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Integration of forage legumes with cereal crops
Livestock Production Science 79 (2003) 213–226 www.elsevier.com / locate / livprodsci
Integration of forage legumes with cereal crops II. Effect of supplementation with lablab hay and incremental levels of wheat bran on voluntary food intake, digestibility, milk yield and milk composition of crossbred cows fed maize–lablab stover or oats–vetch hay ad libitum a, b a ,1 a a D.R. Mpairwe *, E.N. Sabiiti , N.N. Ummuna , A. Tegegne , P. Osuji a
International Livestock Research Institute ( ILRI), Debre Zeit Research Station, P.O. Box 5689, Addis Ababa, Ethiopia b Faculty of Agriculture, Makerere University, P.O. Box 7062, Kampala, Uganda Received 24 April 2001; received in revised form 3 July 2002; accepted 5 July 2002
Abstract This study examined the effects of lablab hay and graded levels of wheat bran supplementation on feed intake, feed degradation characteristics, apparent digestibility, milk yield and milk composition of crossbred cows fed forages from cereal crops 1 legume intercropping (maize / lablab (ML) stover or oats / vetch (OV) hay). Forty eight multiparous crossbred cows arranged in a randomised complete design with eight dietary treatments and six animals per treatment were used in the study. The dietary treatments comprised of either ad libitum ML stover 1 0.5% BW lablab hay or ad libitum OV hay 1 0.9% BW lablab hay, each supplemented with 0, 1.25, 2.50, and 3.75 kg DM of wheat bran. The combination of wheat bran and lablab hay as supplements to cows fed ML stover and OV hay basal diets significantly improved DM digestibility (P , 0.01), which increased (P , 0.001) total DM intake by 21%. DM and OM degradation and the rates of degradation of DM, OM, N and NDF in the rumen were slightly improved by supplementing ML stover or OV hay basal diets with a combination of lablab hay and wheat bran. Supplementation with lablab hay and wheat bran combination increased milk yield by 21% (P , 0.05). Milk yield response to supplementation with lablab hay and wheat bran for the cows consuming ML stover diets was a linear increase (P , 0.001, R 2 5 0.996) with a mean increment of 1.09 kg milk per kg increase of wheat bran DM intake. Milk yield increased by 0.95, 1.3 and 0.95 kg / day for the first, second and third levels of wheat bran supplementation of cows fed ML stover. For OV hay treatments, the relationship between milk yield and increasing levels of wheat bran supplementation was quadratic (P , 0.001; R 2 5 0.990) and the mean response was highest (0.72 kg milk per kg wheat bran intake) at 2.50 kg DM level of wheat bran supplement. Increasing levels of wheat bran supplementation increased milk fat (P , 0.01) and total solids (P , 0.05) for crossbred cows fed ML stover treatments but the increases were not significant for OV hay-based diets. Milk protein concentration was not affected by wheat bran supplementation for both forages. It was concluded from this study that for optimum milk production, cows fed ML stover basal forage should be supplemented with 2.5 kg
*Corresponding author. Present address: Department of Animal Science, Faculty of Agriculture, Makerere University, P.O. Box 7062, Kampala, Uganda. Tel.: 1256-41-532-269. E-mail address: [email protected] (D.R. Mpairwe). 1 Deceased. 0301-6226 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0301-6226( 02 )00178-1
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DM / head / day of wheat bran in addition to 0.5% BW lablab hay while for cows consuming OV hay forage should be supplemented with a combination of 2.5 kg DM / head / day of wheat bran and 0.9% BW lablab hay. The optimum levels of supplementation in this trial were associated with a mean milk yield of 10.94 kg / cow / day for the cows on ML stover basal diet, and 10.84 kg / cow / day milk yield for those on OV hay basal diet. The improved milk yields obtained in the present trial as compared with the results of our previous trial where lablab hay alone was used as a supplement, were attributed to the additive effects of both lablab hay and wheat bran supplements which resulted in improved intake of DM, CP and metabolisable energy. 2002 Elsevier Science B.V. All rights reserved. Keywords: Cereals; Forage legumes; Lablab hay; Wheat bran; Intake; Digestibility; Milk production
1. Introduction Cattle feeding in the tropics and subtropics are often based on natural pastures, hays and / or crop residues, which are generally low in nutritive value and unable to support the higher nutrient requirements of crossbred cows. Cross breeding local cattle (Bos indicus) with exotic species (Bos taurus) has been the policy used in developing countries in the tropics for increasing milk production. Improved feeding of the crossbred cow could be accomplished through the production of better quality forages through intercropping (Khalili et al., 1992, Umunna et al., 1995; Mpairwe, 1998) or appropriate supplementation with locally available by-products. However, the supplement should not have a significantly detrimental effect on intake of the basal food especially where concentrates are scarce and costly relative to forage which are the limiting factors among smallholder farmers in the tropics. Part 1 of this study (Mpairwe et al., 2002b) evaluated the use of forage legume (lablab hay) as a supplement for crossbred (Bos indicus 3 Bos taurus) cows fed maize / lablab (ML) stover or oats / vetch (OV) hay basal forages on diet utilisation and subsequent milk production. The results indicated that supplementation of crossbred cows fed ML stover or OV hay basal forages with increasing levels of lablab hay increased dry matter and crude protein (CP) intake but resulted in moderate levels of animal performance despite the higher increase in CP intake. There was no increased response in milk production of cows given ML stover and OV hay basal forages above supplementation levels of 0.4 and 0.8% BW lablab hay, respectively. The optimum level of lablab hay supplementation that maximised milk production
and reproductive efficiency of crossbred cows was obtained at 0.52 and 0.85% of BW supplementation for ML stover and OV hay basal diets, respectively. The lack of response to higher levels of proteinrich lablab hay supplement was interpreted as resulting from a deficit of dietary energy. It was, therefore, suggested that an intervention with a high energy supplement at the derived optimum levels of lablab hay supplementation may result in higher milk yields. It is important to ensure additivity of the forage legume and wheat bran supplement. Earlier studies (Campling and Lean, 1983) have shown that small amounts of supplementary grains and protein rich concentrates will ensure this. However, it is noteworthy that large amounts of cereal grains are likely to decrease forage intake and result in substitution of concentrate for forage (Campling and Murdoch, 1966). Therefore, the present study was initiated to evaluate the effects of supplementation with a combination of lablab hay and increasing levels of wheat bran, a high energy crop by-product, on feed utilisation and lactation of crossbred cows fed ML stover and OV hay basal diets.
2. Materials and methods
2.1. Animal management and data collection The experiment started at the end of experiment 1 (Mpairwe et al., 2002b). Before the start of the experiment, a total of 60 multiparous crossbred cows were selected from the ILRI—Debre Zeit Research Station dairy herd. The cows were palpated per rectum for ovarian activity and the presence of a corpus luteum. Cows with confirmed presence of a
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corpus luteum were synchronised with estrumate (2 ml per animal) administered intramuscularly, so that they could be inseminated and calve around the same time. The animals were artificially bred at first observed oestrus about 1–5 days after first injection which coincided with 60 days postpartum. After insemination, 48 cows which were confirmed pregnant formed the experimental group. Animal management and data collection were as described by Mpairwe et al. (2002b).
2.2. Feeds, dietary treatments and experimental design Feeds for this experiment (ML stover, OV hay and lablab hay) were produced during the 1996 cropping season and management was as described for experiment 1 (Mpairwe et al., 2002b). Wheat bran was purchased in a single batch from a commercial flour mill. The percentage proportions of cereal and forage legumes in the intercropped feeds used in this study were 67% maize and 33% lablab (i.e. 2:1 ratio) for ML stover, while OV hay comprised 70% oats and 30% vetch (2.3:1 ratio). The experiment was a randomized complete block design with eight dietary treatments and six animals per treatment. The dietary treatments comprised of either ad libitum ML stover 1 0.5% BW lablab hay or ad libitum OV hay 1 0.9% BW lablab hay, each supplemented with 0, 1.25, 2.50, and 3.75 kg DM of wheat bran. The optimum levels of lablab hay supplementation of cows fed ML stover (0.5% BW) and for cows on OV hay (0.9% BW) were determined in experiment 1 (Mpairwe et al., 2002b). The experiment started 2 months before calving and ended 120 days (4 months) after calving for each experimental cow. Body weight changes of the cows and DM of the feeds on offer and refusals were monitored fortnightly and adjustments of the supplement on offer made accordingly. The rest of the experimental procedures were as described in experiment 1.
2.3. Feed degradation characteristics Feed degradation characteristics of intercropped feeds (ML stover and OV hay), supplements (lablab hay and wheat bran) and sululta hay for comparison were established using nylon bags (Mehrez and
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Orskov, 1977). Six rumen fistulated crossbred (Bos taurus 3 Bos indicus) steers (mean live body weight 330637 kg), housed and fed individually were used. The trial was a completely randomized block design with two dietary treatments and three replications. The animals were blocked by weight into two blocks and allotted randomly to two dietary treatments: ML stover supplemented with 0.5% BW lablab hay and 2.8 kg DM wheat bran and OV hay supplemented with 0.9% BW lablab hay and 2.8 kg DM wheat bran. The level of 2.8 kg DM wheat bran supplementation in this trial was the optimum level which was determined with crossbred cows fed ML stover10.5% BW lablab hay and OV hay10.9% BW lablab hay. The animals were adapted for 14 days followed by 6 days for nylon bag incubation. The feeds (ML stover, OV hay, Sululta hay, lablab hay and wheat bran) were ground to pass through a 2-mm screen and DM, OM, N and NDF degradabilities studied (Mehrez and Orskov, 1977). Bags of Sululta and lablab hays were incubated in all the animals together with either ML stover bags for the animals consuming ML basal diet or OV hay bags for animals fed OV hay basal diet. Wheat bran bags were incubated in the wheat bran supplemented animals only. The procedure for nylon bag incubation and processing were as described in experiment 1.
3. Results
3.1. Chemical composition and degradation characteristics of the feeds The chemical composition of the feeds is presented in Table 1. Organic matter (OM) concentrations were similar among the forage feedstuffs and was highest in wheat bran. The two basal forages did not vary much in their NDF concentrations but OV hay had higher CP concentration than ML stover. Mineral concentrations were similar in both basal forages and were higher than the estimated requirements of rations for dairy cattle (experiment 1) indicating that concentrations of the essential minerals for dairy cows were not limiting in the two basal forages. The level of CP in ML stover (8.2% CP) was lower while that in OV hay (11% CP) was
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Table 1 Chemical composition (g / kg DM) of experimental feeds
Dry matter (g / kg) Organic matter Neutral detergent fibre (NDF) NDF–Nitrogen (g / kg NDF) Acid detergent fibre Acid detergent lignin Crude protein (N 36.25) Minerals (g / kg DM) Calcium Phosphorus Magnesium Potassium a
Maize / lablab stover
Oats / vetch hay
Lablab hay
Offer
Refusal
Offer
Refusal
Offer
Refusal
888 883 593 2.82 381 45.4 81.9
852 909 635 ND ND ND 48.7
899 885 602 3.67 390 49.5 109.9
858 899 722 ND ND ND 54.4
901 885 412 2.62 346 60.7 148.8
885 884 538 ND ND ND 86.9
8.1 3.9 2.7 22.8
ND ND ND ND
6.4 5.5 2.0 31.9
ND ND ND ND
17.1 5.4 3.8 29.7
ND ND ND ND
Wheat bran Offer
Grass a (sululta) hay
868 946 487 5.76 134 27.7 161.2
920 888 624 ND ND ND 61.9
1.7 11.9 5.2 13.1
ND ND ND ND
Grass hay was used in the degradability studies. ND, not determined.
within the range of 11–12% CP required for moderate levels of ruminant production (ARC, 1980). However, these CP concentrations in the two basal forages were higher than the limiting level (6–8% CP) below which appetite and forage intake are depressed (Minson, 1982; Forbes, 1986). The supplements (lablab hay and wheat bran) had the highest CP and lowest NDF concentrations relative to the basal diets (ML stover and OV hay). Mineral concentrations were also higher in the supplements than in the basal forages. Lablab hay had higher calcium concentration (17.1 g / kg) than wheat bran (1.7 g / kg) but the concentration of phosphorous was higher in wheat bran (11.9 g / kg) than in lablab hay (5.4 g / kg). Crude protein concentrations were higher while the NDF concentrations were lower for the two basal forages than that in grass (Sululta) hay; thus showing the superiority of intercropped feeds over the commonly used pasture hays. Rumen degradation characteristics of the feedstuffs are presented in Table 2. Potential DM and OM degradabilities were significantly (P,0.05) higher in wheat bran than in lablab hay but the effective degradabilities were similar. However, lablab hay had higher DM and OM degradation rate (P,0.001) than wheat bran. The potential and effective DM, OM, N and NDF degradabilities were similar for ML stover and OV hay basal diets and did not differ significantly (P.0.05) from that of grass hay. DM, OM and NDF degradation rates did not differ between the basal diets, wheat bran and the
grass hay but wheat bran had faster N degradation rate (P,0.001 than the basal diets.
3.2. Nutrient intake and diet apparent digestibility The results of the effects of lablab hay and wheat bran supplementation of cows fed ML stover or OV hay basal diets on intake and diet apparent digestibility are presented in Table 3. Dry matter intake of the basal diet tended to be higher for ML stover treatments than for cows on OV hay treatments. Total DM intake for the control treatments was significantly (P,0.01) higher for cows fed OV hay10.9% BW lablab hay than for cows consuming ML stover10.5% BW lablab hay. Wheat bran supplementation did not affect ML stover intake at 1.25 kg DM level of supplement but higher levels of wheat bran supplementation significantly (P,0.05) decreased ML stover intake. However, there was no significant difference in basal diet intake between the control treatment and supplemented ML stover treatments up to the level of 2.50 kg DM wheat bran. Maize–lablab stover intake was significantly (P, 0.01) reduced at the highest level of wheat bran (3.75 kg DM). For OV hay treatments, increasing levels of wheat bran supplementation significantly (P,0.001) decreased OV hay DM intake. Total DM intake for the control treatment was significantly (P,0.001) lower than for the wheat bran supplemented ML stover treatments; and it increased with increasing levels of wheat bran supple-
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Table 2 Degradation constants (g / kg DM) of dry matter (DM), organic matter (OM), nitrogen (N) and neutral detergent fibre (NDF) of experimental feeds
DM
OM
N
NDF
Maize/lablab stover (1)
Oats/vetch hay (2)
Lablab hay (3)
Wheat bran (4)
Sululta hay (5)
S.E.D. (n54)
Significance level (P) 1&2 vs. 5
1&2 vs. 3
1&2 vs. 4
3 vs. 4
Solubility a b PD ED TL c
293 220 526 746 539 24.3 0.039
302 251 468 719 525 20.6 0.037
419 295 489 784 693 23.1 0.102
474 300 544 844 693 211.3 0.047
213 156 502 658 425 21.1 0.030
19.98 20.02 11.31 12.22 2.63 0.01
0.001 ns 0.001 0.001 ns ns
0.001 ns 0.001 0.001 ns 0.001
0.001 0.05 0.001 0.001 0.001 ns
ns 0.01 0.001 ns 0.01 0.001
Solubility a b PD ED TL c
232 211 537 748 512 20.3 0.037
270 186 531 717 501 21.7 0.037
382 280 489 769 670 22.8 0.100
477 302 543 845 681 213.8 0.040
166 146 492 638 397 1.2 0.030
19.29 20.54 11.75 12.97 2.47 0.01
0.01 0.05 0.001 0.001 ns ns
0.001 0.01 0.001 0.001 ns 0.001
0.001 ns 0.001 0.001 0.001 ns
ns 0.01 0.001 ns 0.001 0.001
Solubility a b PD ED TL c
466 300 480 780 698 25.8 0.099
431 274 483 757 680 22.9 0.107
532 244 676 920 849 23.0 0.153
606 240 698 938 889 24.9 0.227
399 107 408 515 440 22.4 0.033
20.14 28.83 24.77 13.31 2.11 0.038
0.001 0.01 0.001 0.001 ns 0.05
0.05 0.001 0.001 0.001 ns ns
0.01 0.001 0.001 0.001 ns 0.001
ns ns ns 0.001 ns 0.05
Solubility a b PD ED TL c
54 84 596 680 384 4.1 0.037
82 104 550 654 376 4.8 0.035
154 191 426 617 462 0.2 0.068
110 202 569 771 421 20.1 0.029
58 69 547 616 325 5.0 0.029
25.06 25.21 16.93 17.90 1.77 0.008
ns ns 0.001 0.001 ns ns
0.001 0.001 0.001 0.001 0.01 0.001
0.001 ns 0.001 0.01 0.01 ns
ns 0.001 0.001 0.01 ns 0.001
a5zero time intercept; b5insoluble but potentially (slowly) degradable component; c5the rate of degradation of b component; PD5(a 1 b), potential degradability (g / kg); TL5lagtime (h); ED5effective degradability (g / kg) at outflow rate of 0.03; ns5not significant; S.E.D.5standard error of difference.
mentation. However, there were no significant differences in total DM intake among the wheat bran supplemented treatments. Total DM intake for the control treatment of OV hay-based treatments was not different from the wheat bran supplemented treatments but among the supplemented treatments, it significantly (P,0.01) increased with increasing levels of wheat bran. Substitution rates (SR) were calculated as the ratio of the difference in intake of ML stover or OV hay between the control treatment and the supplemented treatment to the quantity of wheat bran supplement. SR were 20.08, 0.25 and 0.43 (i.e. 21.4, 8.5 and
22.5%) for ML stover-based diets and 0.83, 0.66, 0.54 (i.e. 15, 25, and 31.5%) for OV hay based diets at 1.25, 2.50 and 3.75 kg DM levels of wheat bran supplementation, respectively. This indicated that wheat bran supplementation did not substitute the basal diet up to the level of 1.25 kg DM in ML stover based diets but substituted OV hay at all levels of supplementation. Intake of organic matter (OMI) and digestible organic matter (DOM) for wheat bran supplemented treatments were significantly higher (P,0.01) for ML stover diets and (P,0.001) for OV hay diets than the control treatments. Increasing levels of
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Table 3 Mean daily nutrient intake and apparent digestibility by crossbred cows fed ad libitum maize / lablab10.5% BW lablab hay (ML1LB) or oats / vetch hay10.9% BW lablab hay supplemented with graded levels of wheat bran
Basal diets:
Treatments
S.E.D.
Significance (P)
ML stover10.5% BW lablab (ML) OV hay10.9% BW lablab (OV)
(n56)
Treatment
ML vs. OV
ML vs. SP
OV vs. SP
Wheat bran (kg DM): Dry matter intake (kg/day) Basal diet Lablab hay Wheat bran Total DM digestibility (g/kg) Organic matter OMI (kg/day) DOMI (kg/day) OMD (g/kg) DOMD (g/kg) CP intake (kg/day) Digestibility (g/kg) NDF intake (kg/day) Digestibilty (g/kg) Metabolisable energy MEF (MJ/kg DM) Intake (MJ/head/day)
0
7.1 2.2
1.25
2.50
3.75
9.3 658
7.2 2.1 1.2 10.5 683
6.5 2.2 2.4 11.2 705
5.5 2.2 3.7 11.4 678
8.1 6.4 677 591 1.02 676 4.95 613
9.2 7.4 701 619 1.20 713 5.56 627
9.9 8.2 725 645 1.36 743 5.83 654
10.2 8.0 700 627 1.48 729 5.80 590
–
0
6.3 4.1
1.25
2.50
3.75
4.7 4.1 2.4 11.2 688
4.3 4.1 3.7 12.1 700
0.44 – – 0.46 16.46
0.001
ns
ns
0.001
– 10.4 637
5.3 4.1 1.2 10.6 672
0.001 0.01
0.01 ns
0.001 0.05
ns 0.01
9.3 7.5 695 617 1.53 727 5.07 532
9.4 7.8 717 632 1.58 749 5.05 587
10.0 8.1 714 639 1.71 772 5.23 599
10.9 0.40 8.9 0.50 726 14.33 653 12.68 1.93 0.04 787 7.59 5.56 0.29 595 33.00
0.001 0.001 0.01 0.001 0.001 0.001 ns ns
0.01 0.01 0.01 0.01 0.001 0.001 ns ns
0.001 0.001 0.01 0.001 0.001 0.001 0.01 ns
0.05 ns ns ns 0.001 0.001 ns ns
0.001 0.001
0.01 0.01
0.001 0.001
ns ns
9.10 9.53 9.93 9.65 9.50 9.72 9.83 10.1 85.6 100.7 111.7 110.5 102.2 105.3 111.5 123.6
0.19 6.79
OMD5digestibility of the organic matter; DOMD5digestible organic matter in the dry matter; MEF5metabolisable energy of feed (MEF50.153DOMD%); ML vs. SP5(ML10.5% Lablab) vs. (ML10.5% BW Lablab1wheat bran); OV vs. SP5(OV10.9% BW Lablab) vs. (OV10.9% BW Lablab1 wheat bran); ns5not significant; S.E.D.5standard error of difference.
wheat bran led to increased OMI and DOMI but the increases were not significant for OV hay based diets. Diet apparent DM digestibility (DMD) and organic matter (OMD) were improved by wheat bran supplementation when compared with ML stover1 0.5% BW and OV hay10.9% BW lablab hay treatments. However, there were no significant differences in DMD among the wheat bran supplemented diets. Digestible organic matter in the dry matter (DOMD) for OV hay10.9% BW lablab hay was higher than that of ML stover10.5% BW lablab hay. Supplementation improved DOMD but there was no significant difference among the supplemented treatments. Treatment effects on crude protein intake (CPI) were highly significant (P,0.001) (Table 3). CPI with ML stover10.5% BW lablab hay was lower than that of OV hay10.9% BW lablab hay. CP intake of wheat bran supplemented treatments was significantly (P,0.001) higher than the control treatments (ML stover10.5% BW lablab hay and
OV hay10.9% BW lablab hay). NDF intake and digestibility were similar in both ML10.5% BW lablab hay and OV hay10.9% lablab hay. However, supplementation with wheat bran led to improved NDF intake for cows consuming ML stover diets (P,0.01) while for OV hay the increase was not significant. NDF digestibility was not affected by the different dietary treatments. Metabolisable energy of the feed (MEF) for ML stover10.5% BW lablab hay was lower than that for OV hay10.9% BW lablab hay. Wheat bran supplementation significantly (P,0.001) increased MEF from 9.10 to 9.93 MJ / kg DM for ML stover-based diets and from 9.50 to 10.1 MJ / kg DM for OV hay diets but the increase was not significant for OV hay-based diets. Wheat bran supplementation increased metabolisable energy intake (MEI) from 85.6 to 110.5 and from 102.2 to 123.6 MJ / head / day for ML stover and OV hay treatments, respectively; but there were no significant differences among OV hay treatments. The mean responses to increased ME
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intake (estimated according to MAFF, 1987) were 0.038 and 0.058 kg milk per MJ MEI for ML stoverand OV hay-based diets, respectively.
3.3. Mineral intake and Ca: P ratio The effect of wheat bran supplementation of cows fed ML stover or OV hay basal forages at optimum levels of lablab hay on mineral intakes (Ca, P, Mg and K) and the calcium to phosphorous (Ca:P) ratios are presented in Table 4. Chemical composition of the feeds (Table 1) showed that the concentrations of Ca, P, Mg and K differed between ML stover, OV hay, lablab hay and wheat bran. Consequently, treatment effects on mineral intake and Ca:P ratio were highly significant (P,0.001). Ca intake from ML stover10.5% BW lablab hay based diets was significantly (P,0.001) lower than that from OV hay10.9% BW lablab hay diets. Mg intake was similar for both control diets while increasing levels of wheat bran supplementation significantly (P, 0.001) increased Mg intake in both forage diets but there were no significant differences among the
219
wheat bran supplemented treatments. ML stoverbased diets promoted significantly (P,0.001) lower K intake than OV hay treatments but there were no significant treatment differences within each forage type. Calcium to phosphorus ratio was significantly (P, 0.001) higher for the control treatments than the wheat bran supplemented treatments. Ca:P ratios of ML stover10.5% BW lablab hay (2.41) and OV hay10.9% BW lablab hay (2.04) control treatments were similar to the ratios obtained in experiment 1, thus, indicating the repeatability of the results. However, supplementation with wheat bran significantly (P,0.001) reduced the Ca:P ratios in both forage diets but were within the recommended range 1–2:1 for cattle (McDonald et al., 1987).
3.4. Milk yield and milk composition The results for the effects of lablab hay and wheat bran supplementation on milk yield and milk composition are presented in Table 5. There were no significant (P.0.05) differences in milk yield be-
Table 4 Mineral intake a by crossbred cows fed ad libitum maize / lablab stover10.5% BW lablab hay (ML1LB) or oats / vetch hay10.9% BW lablab hay (OV1LB) supplemented with graded levels of wheat bran Treatments Basal diet
Mean mineral intake (g / head / day) Wheat bran level (kg DM)
Calcium
Phosphorus
Magnesium
Potassium
Ca:P
ML1LB T1 T2 T3 T4
0 1.25 2.50 3.75
94 96 95 88
39 54 66 77
27 34 39 43
226 242 246 238
2.41 1.79 1.43 1.12
OV1LB T5 T6 T7 T8
0 1.25 2.50 3.75
115 106 103 105
58 66 77 90
29 32 37 44
327 307 302 308
2.04 1.62 1.34 1.16
S.E.D. (n56) Significance Treatment T1 vs. T5 T1 vs. (T21T31T4) T5 vs. (T61T71T8) (T21T31T4) vs. (T61T71T8) a
3.62
2.40
1.05
0.001 0.001
0.001 0.001 0.001 0.001 0.001
0.001 ns 0.001 0.001 ns
ns 0.05 0.001
13.87 0.001 0.001 ns ns 0.001
0.03 0.001 0.001 0.001 0.001 0.001
Mineral intake from the experimental forages only (in addition, the animals were provided with mineral blocks). ns5not significant; S.E.D.5standard error of difference.
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Table 5 Mean daily milk production characteristics and mean body weight changes of crossbred cows fed ad libitum maize / lablab10.5% BW lablab hay (ML1LB) or ad libitum oats / vetch hay10.9% BW lablab hay (OV1LB) supplemented with graded levels of wheat bran Treatments Basal diets: Wheat bran (kg DM): Milk production Milk yield (kg/day) Fat yield (g/day) Protein yield (g/day) Total solids (g/day)
ML stover10.5% BW lablab (ML) 0
1.25
2.50
3.75
OV hay10.9% BW lablab (OV) 0
1.25
2.50
S.E.D.
Significance (P)
(n56)
Treatment
ML vs. OV
ML vs. SP
OV vs. SP
0.05 0.001 0.001 0.001
ns ns ns ns
0.01 0.001 0.01 0.001
0.05 0.01 0.01 0.01
3.75
8.69 9.64 10.94 11.89 9.04 9.89 10.84 11.15 0.85 360 428 522 564 409 471 549 567 36.16 256 294 340 366 281 318 354 360 24.98 1043 1211 1425 1442 1130 1294 1439 1435 100.07
Milk composition (g/kg) Fat Protein Total solids
43.2 30.5 125.1
44.6 30.7 126.1
48.8 31.5 131.7
50.7 32.5 128.6
45.8 31.3 125.6
47.9 32.1 131.0
51.4 33.0 133.6
52.3 33.5 132.6
2.53 0.95 3.07
0.01 0.05 0.05
ns ns ns
0.01 ns 0.05
ns ns ns
Body weight changes (calving to 120 days) Calving weight (kg) LW at 120 days (kg) Mean weight change (kg) Mean weight gain (g/day)
434 408 23.8 29.8
451 403 25.83 227.3
463 418 1.17 210.2
463 426 27.1 6.9
445 419 21.2 18.9
446 389 24.6 215.5
441 382 24.0 218.9
456 438 24.5 223.5
12.97 13.97 11.82 48.63
0.05 0.05 ns ns
ns ns ns ns
0.01 ns ns ns
ns 0.05 ns ns
ML vs. SP5(ML10.5% lablab) vs. (ML10.5% BW lablab1wheat bran); OV vs. SP5(OV10.9% BW lablab) vs. (OV10.9% BW lablab1 wheat bran); LW5live weight; ns5not significant; S.E.D.5standard error of difference.
tween the control treatments although animals on OV hay10.9% BW lablab hay tended to have higher milk yield than those on ML stover10.5% BW lablab hay. For ML stover-based treatments, wheat bran supplementation significantly (P,0.01) increased milk yield from 8.69 to 11.89 kg / head / day while for OV hay-based diets there was also a significant (P,0.05) increase in milk yield from 9.04 to 11.15 kg / head / day. The response in milk yield for ML stover treatments was a linear increase (P,0.001, R 2 50.996), resulting in a mean increment of 1.09 kg milk per kg increase in the wheat bran DM intake (Fig. 1). Milk yield increased by 0.95, 1.3 and 0.95 kg / day for the first, second and third levels of wheat bran supplementation of cows fed ML stover. The corresponding increases in milk yields per kg of wheat bran intake as compared to the control diet (T1) were 0.76, 0.90 and 0.85 kg / day at 1.25, 2.50 and 3.75 kg DM levels of wheat bran, respectively. This indicated that milk yield of crossbred cows fed ML stover basal forage was optimised when supplemented with a combination of 0.5% BW lablab hay and 2.50 kg DM wheat bran. For OV hay treatments, although the linear re-
Fig. 1. Milk yield regression response curve for crossbred cows fed ML stover10.5% BW lablab hay supplemented with graded levels of wheat bran.
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sponse was significant (P,0.05, R 2 50.963), there was a strong quadratic relationship (P,0.001, R 2 5 0.990) between milk yield and increasing levels of wheat bran supplementation (Fig. 2). Milk yield increased by 0.85, 0.95 and 0.31 kg / head / day and the corresponding increases in milk yields per kg wheat bran intake compared with the control diet were 0.68, 0.72 and 0.56 kg / day at 1.25, 2.50 and 3.75 kg DM levels of wheat bran supplementation, respectively. The mean response to wheat bran supplementation was highest at the second increment of supplement (0.72 kg milk per kg wheat bran intake) as compared with responses of 0.68 and 0.56 to the first and third increments, respectively. The results, thus indicated that for crossbred cows fed OV hay basal forage, milk yield was optimised when the cows were supplemented with a combination of 0.9% BW lablab hay and 2.50 kg DM wheat bran per cow each day. Treatment effects were significant for milk fat, protein and total solids (Table 5). However, there were no significant differences in any of the milk
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components studied between the control treatments (T1 vs. T5). Increasing levels of wheat bran supplementation significantly increased the concentrations of milk fat (P,0.01) and total solids (P,0.05) for crossbred cows fed ML stover treatments. Similarly, for OV hay-based diets, the concentrations of milk fat and total solids increased with increasing levels of wheat bran supplementation but the differences were not significant (P.0.05). Milk protein concentration was not affected by wheat bran supplementation. Milk components (fat, protein and total solids) yield followed a similar trend as milk yield. There were no significant differences in milk fat, protein and total solids yield between the control diets (T1 and T5). Increasing levels of wheat bran supplementation significantly increased milk fat, protein and total solids yield (P,0.001) for cows fed ML stover treatments and (P,0.01) for cows on OV hay treatments.
4. Discussion
4.1. Chemical composition and degradability of the feeds
Fig. 2. Milk yield regression response curve for crossbred cows fed OV hay10.9% BW lablab hay supplemented with graded levels of wheat bran.
The quality of ML stover used in this experiment was lower than that used in our previous trial (Mpairwe et al., 2002b) and was attributed to the unexpected rains of November 1996 up to January 1997 that occurred during the harvesting and storage period. During the drying process, some leaves, especially of the lablab component in the harvested material, became rotten due to excessive moisture while others shattered because the maize component in the mixture took longer to dry. As a result the proportion of lablab in ML stover was lower than expected and hence the lower CP concentration when compared with the ML stover used in experiment 1. The better quality of OV hay used in the present trial was attributed to the well-distributed rains of June to September 1996 and to the subsequent dry conditions in October. Therefore, the OV hay, which was harvested at the beginning of October, was dried and stored in a favourable good weather for haymaking. Consequently, the proportion of vetch in the OV hay was higher than that of the OV hay used in experiment 1 and hence the higher CP concentration.
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4.2. Nutrient intake and diet apparent digestibility The differences in DM intake between the ML stover and OV hay-based treatments were attributed to the differences in quality of the two basal forages. It has been noted that if the basal diet has a low nitrogen content, the addition of a forage legume will increase the nitrogen content of the total diet. This is likely to increase feed intake and the rate of degradation of the basal diet in the rumen (Topps, 1997). This, therefore, explains why supplementation increased total DM intake for ML stover-based treatments while it did not affect total DM intake for OV hay-based treatments when compared with the control treatments. The addition of lablab hay into ML stover (which had low CP content) treatments increased total DMI as opposed to OV hay which was of better quality (high CP) when compared with the control treatments. The improved total dry matter intake observed in this experiment was associated with the improved DMD and OMD which in turn was attributed to the increased rates of DM and OM degradation (Mpairwe, 1998) deriving from supplementation with wheat bran. In addition, from the results of Mpairwe (1998), the reduced total mean retention time with increasing levels of wheat bran could have contributed to the improved total DM and OM intake. On the other hand, the increased CPI experienced in this study was attributed to the intake of both lablab hay and wheat bran, which were high in CP. When compared with calculated values, the CP intakes of the cows in this trial were adequate for estimated CP intake (MAFF, 1987) requirements for maintenance and milk production (excluding live weight changes) except for the control diet of ML stover-based diets, which indicated a deficit of 273 g CPI. Supplementing cows consuming ML stover10.5% BW lablab hay with 2.5 kg DM wheat bran and for cows on OV hay10.9% BW lablab hay with 1.25 kg DM increased total DM intake without significant substitution of the basal diet. Consequently, total OM intake increased by the amount of supplement given. However, when wheat bran was given at a higher level (3.75 kg DM / day) the DMI of ML stover was reduced by 1.6 kg (22.5%) and the DMI of OV hay was reduced by 2.0 kg (31.8%), thus, indicating that substitution of the basal diet by wheat bran was
greater for OV hay than for ML stover. Campling and Murdoch (1966) reported that when concentrates were given to cows the substitution rate tended to be greatest with the hays of highest digestibility. Similarly, Faverdin et al. (1991) observed that substitution rate was greater with silage that had an energy value superior to that of hay. Therefore, the better nutritive value (higher CP content and ME) of OV hay forage could have contributed to the higher substitution rates by wheat bran supplementation than was observed in ML stover. The substitution rates obtained in this experiment were lower than the SR obtained by Mpairwe et al. (2002b) indicating that supplementing cows fed ML stover or OV hay with a combination of lablab hay and wheat bran reduced the substitution effects which were experienced when lablab hay alone was used as a supplement. The estimated MEI requirements for maintenance and milk production (excluding body weight changes) of a lactating dairy cow weighing 400 kg and producing 10 kg / day milk of 4.8% butter fat) was 106 MJ / head / day (MAFF, 1987). For the control treatments and at the lowest level of wheat bran (1.25 kg DM) supplementation in both forages, the results indicated a deficit in MEI that was highly significant (P,0.001) for ML10.5% BW lablab hay diet which had a negative MEI of 20.4 MJ / head / day. The lower MEI in the control treatment for ML stover-based diets as compared to the wheat bran supplemented treatments in this experiment was attributed to the lower total DM and OM intakes (Table 3). However, wheat bran supplementation of cows fed ML stover10.5% BW lablab hay or OV hay10.9% BW lablab hay at the level equal to and higher than 2.50 kg DM of wheat bran met the estimated ME requirements of the cows. Compared with the results in experiment 1 (Mpairwe et al., 2002b), the mean ME intake (110.6 MJ / head / day) for the wheat bran supplemented treatments in addition to the optimum level of lablab hay was similar to the mean ME intake (108.1 MJ / head / day) obtained when lablab hay alone was used as a supplement. The mean responses to increased ME intake (estimated according to MAFF, 1987) were 0.038 and 0.058 kg milk per MJ MEI for ML stover- and OV hay-based diets, respectively. These values were higher than the response of 0.037 and 0.044 kg milk per MJ ME for ML and OV diets,
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respectively, in response to wheat-middlings (Khalili et al., 1994). The values, however, were lower than the response of 0.14 kg milk per MJ change in intake of cows producing 20 kg / day (Broster and Thomas, 1981). The improved metabolisable energy intake in the present trial was associated with improved OMI and DOMD as a result of lablab hay and increasing levels of wheat bran in the diets.
4.3. Mineral intake The lower Ca intake for ML stover10.5% BW lablab hay based diets than for OV hay10.9% lablab hay diets was attributed mainly to the difference in the amount of lablab hay intake. The amount of lablab hay consumed in the OV hay based diets was higher than that consumed by animals fed ML stover diets (Table 1). Increasing levels of wheat bran supplementation tended to decrease Ca intake while P intake increased with increasing levels of wheat bran supplementation in both forages. The decrease in Ca intake was associated with increase in wheat bran intake which had very low Ca concentration while the increased P intake was attributed to the intake of both lablab hay and increasing levels of wheat bran which both had substantial quantities of P (Table 1). Supplementation with wheat bran reduced the Ca:P for both ML stover and OV hay based diets and the values were within the recommended range of 1–2:1 for cattle (McDonald et al., 1987). The results of this experiment therefore revealed the advantage of supplementing intercropped feeds with a combination of lablab hay and wheat bran. The high levels of Ca in lablab hay were probably counterbalanced by the high levels of P in wheat bran and thus optimising the Ca:P ratio. Furthermore, the results in this study indicated that the intakes of Ca and P were adequate for estimated (MAFF, 1987) mineral requirements (36.6 and 27.4 g / head / day for Ca and P, respectively) of a dairy cow of mean live weight 400 kg, producing 8–13 kg milk of 4% butter fat. The combination of lablab hay and wheat bran supplements, thus satisfied the essential mineral requirements for cattle especially Ca and P which are the most limiting minerals for milk production and often encountered in high grade cows fed low quality forages.
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4.4. Milk yield and milk composition The tendency for the animals on OV hay10.9% BW lablab hay to have higher milk yield than those on ML stover10.5% BW lablab hay was associated with the higher CP concentration of OV hay (Table 1) and the higher amount of lablab hay offered. This resulted in higher CP intake and CP digestibility of cows fed OV10.9% BW lablab hay (Table 3) than the cows on ML stover10.5% BW lablab hay. The average daily milk yield for each of the 17-week lactation period of the trial (Fig. 3) clearly showed that milk production was always higher for crossbred cows receiving wheat bran supplementation than for the cows on the control treatments. This showed that additional wheat bran supplementation added to lablab hay increased milk yield of crossbred cows fed ML stover or OV hay basal diets. The increased milk fat with wheat bran supplementation may have been due to increasing concentrations of rumen butyrate (Mpairwe, 1998). Previous studies have shown increased milk fat to result from increased rumen butyrate (Bowman and Huber, 1967; Broster et al., 1970). The trend toward increased milk protein concentrations could be attributed to the higher levels of CP intake with increasing levels of wheat bran supplementation which has been reported to increase milk yield and milk protein concentration (DePeters and Cant, 1992; Phipps, 1994). The higher milk production of crossbred cows fed ML stover and OV hay basal diets supplemented with lablab hay and wheat bran than in the previous experiment when the crossbred cows fed the same basal forages were supplemented with lablab hay only was explained by the greater degradabilities of DM, OM, N and NDF reported by Mpairwe (1998). In addition, the combination of lablab hay and wheat bran supplementation had higher values of degradation rate constants (c value) than when the two forages were fed to crossbred cows supplemented with lablab hay alone. The differences between the two experiments suggest that probably there was more of both energy and nitrogen available for the rumen microbes when the cows fed ML stover and OV hay basal forages were supplemented with a combination of lablab hay and wheat bran than when supplemented with lablab hay alone. This was evidenced by the results for crude protein intake (CPI)
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Fig. 3. Lactation curves for crossbred cows fed maize / lablab stover10.5% BW lablab hay (ML1LB) or oats / vetch hay10.9% BW lablab hay (OV1LB) basal forages supplemented with graded levels of wheat bran.
and metabolisable energy intake (MEI) (Table 3). Crude protein and metabolisable energy intakes of the wheat bran supplemented treatments were above the estimated CPI (1.29 kg) and MEI (106 MJ / head / day) requirements for maintenance and milk production of a dairy cow weighing 400 kg, producing 8 kg / day milk of 4% butter fat. Since wheat bran provided additional crude protein and energy (Table 1) for the crossbred cows it was difficult to separate the effect of increased protein and / or energy supply on feed intake, apparent digestibility and milk yield. Therefore, the results of this trial could not explain whether the lower milk yields obtained with lablab hay supplementation (experiment 1) were as a result of inadequate energy supply to the cows during lactation. Instead, the improved milk yields obtained in the present trial as compared with the results of experiment 1 were attributed to the additive effects of improved feed intake, CP intake and ME intake from both lablab hay and wheat bran supplements. Therefore, it was suggested that research involving the use of additional energy supplements from non-proteinaceous feed sources like molasses should be conducted to establish the lower milk yields experienced when the crossbred cows fed ML stover and OV hay basal forages were supplemented with lablab hay alone. The present study showed that the mean milk yield response to wheat bran supplementation was highest at the second increment of wheat bran supplement (0.90 kg for ML and 0.72 kg for OV hay milk yield per kg wheat bran intake). This indicated that milk
yield of crossbred cows fed ML stover and OV hay basal forages was optimised when supplemented with a combination of either 0.5% BW lablab hay for ML stover or 0.9% BW lablab hay for OV hay with 2.50 kg DM wheat bran. At the current farm gate price of milk (US$0.286 per kg) in Ethiopia, the responses in milk yield per kg DM wheat bran fed were US$0.217, 0.257 and 0.243 for the first, second and third increments of wheat bran, respectively, in ML stover-based diets. For OV hay-based diets the corresponding responses in milk yield to wheat bran supplementation were US$0.195, 0.206 and 0.160 per kg DM wheat bran fed. The current cost of wheat bran in Debre Zeit, Ethiopia is about US$0.071 / kg. Based on the treatment milk yield responses per kg wheat bran and the corresponding monetary values, it was recommended that for optimum milk yields, crossbred cows fed ML stover10.5% BW lablab hay or OV hay10.9% BW lablab hay should be supplemented with additional 2.50 kg DM wheat bran. However, there is need for more research to determine suitable economic optimum levels for smallholder that should be adopted in relation to local quantities and qualities of the basal forages and lablab that can be expected. The optimum levels of supplementation in this trial were associated with a mean milk yield of 10.94 kg / cow / day, for the cows on ML stover basal diet; and 10.84 kg / cow / day milk yield, for those on OV hay basal diet. At these optimum levels of lablab hay and wheat bran supplementation when compared with the optimum level where lablab hay supplement
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alone in our previous trial (Mpairwe et al., 2002b), milk yield increased by 24.7% (8.77 vs. 10.94 kg / head / day) for ML based diets and 12% (9.68 vs. 10.84 kg / head / day) for cross bred cows fed OV hay diets. These improvements were attributed to the additive effects of improved intake of feed DM, CP and ME from both lablab hay and wheat bran supplements. Differences in the nutritional value of the two basal forages were associated with the better quality of OV hay, which had higher CP content than ML stover (Table 1). OV hay was harvested at milk stage and hence had higher CP content than ML stover, which was harvested at full maturity of the cereal component in the mixture. As such, the difference in the response of the cows was attributed to the difference in the nutritional value of the two forages whereby supplementation benefited more the low quality ML forage than OV hay.
4.5. Socio-economic implications of the study There is need to develop feeding systems based on locally available feed resources in order to improve production in smallholder dairy farming systems in the tropics. In Eastern and southern Africa, cereal crop residues especially maize stovers are readily available as a by-product of maize grain production and most farmers collect and store it for dry season feeding. Smallholder farmers grow cereal crops especially maize although not in very large amounts owing to the small land size per household. Methu et al. (2002) reported that these smallholders produce an average of 1.8 tonnes of stover per household per year. This is substantial amount given that the average herd size for smallholders is normally two milking cows and two calves and that maize stover is mainly used as a dry season feed. Lablab grows well in mixtures with maize or soghum and can be interplanted into banana and coffee plantations and whatever space available on farm. It produces herbage high in DM and CP and improves the quality of the stovers (Mpairwe et al., 2002a). Moreover, lablab is widespread throughout the tropics especially in Africa as a food crop (Gohl, 1975). There is increasing emphasis on the use of lablab and is being promoted as a fodder crop for supplementing low quality forages in intensive smallholder dairy production systems in Eastern and Southern Africa (Kiflewahid and Mosimanyama, 1987; Sabiiti et al.,
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1994; Mpairwe, 1998). Agro-industrial crop by products like wheat bran are readily available from flour mills within the region since maize and wheat flour are the major stable foodstuffs in the developing tropics. Therefore, the technology of utilising lablab to improve the quality of cereal stovers and as a supplement in combination with wheat bran can be an effective strategy to improve intake and milk production of crossbred cows in smallholder farming systems.
5. Conclusions It was concluded that although forages resulting from cereal and forage legume intercropping are of superior quality when compared with their respective cereal crop residues, there is need for supplementation when they are fed to crossbred cows for optimum milk production. In smallholder dairy production systems in the tropics where resources are scarce, supplementation could be achieved by utilising forage legumes (lablab hay) and locally available agro-industrial crop by-products like wheat bran. The results clearly showed that additional wheat bran supplementation added to lablab hay increased milk yield of crossbred cows fed ML stover or OV hay basal diets thus confirming the hypothesis of this study. It was, therefore, recommended that for optimum milk yield, crossbred cows consuming ML stover basal forages should be supplemented with a combination of 0.5% BW lablab hay and 2.50 kg DM wheat bran, while a combination of 0.9% BW lablab hay and 2.50 kg DM wheat bran was recommended as supplement for cows consuming OV hay basal forages.
Acknowledgements The authors are grateful to the International Livestock Research Institute (ILRI) and the Livestock Services Project (World Bank) in the Ministry of Agriculture, Animal Industry and Fisheries, Uganda for funding this study. We are greatly indebted to the late Professor N.N. Ummuna for the close supervision he rendered to this research and this paper is dedicated to him. The technical assistance of the staff members of ILRI, both at the Debre Zeit
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Research Station and Addis Ababa who contributed to this study during data collection and analysis is gratefully acknowledged. The computing skills of the staff of the Biometrics Department at ILRI, especially Mamadou Diedhiou, Zerihun Tadesse, Amare Atale and Aklilu Bogale, are also highly appreciated.
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purpureus) in by-product based diets for lactating cows in Botswana. In: Said, A.N., Dzowela, B.H. (Eds.), Overcoming Constraints to the Efficient Utilisation of Agricultural Byproducts as Animal Feed. International Livestock Centre for Africa (ILCA), Addis Ababa, Ethiopia, pp. 155–175. Ministry of Agriculture, Fisheries and Food (MAFF), 1987. Energy Allowances and Feeding Systems For Ruminants. Reference Book 433. Her Majesty’s Stationery Office, London, pp. 68–73. McDonald, P., Edwards, R.A., Greenhalgh, J.F.D., 1987. Animal Nutrition, 4th Edition. Longman, London, 543 pp. Mehrez, N.P., Orskov, E.R., 1977. A study of the artificial fibre bag technique for determining the digestibility of feeds in the rumen. J. Agric. Sci. 88, 645–650. Methu, J.N., Owen, E., Abate, A.L., Tanner, J.C., 2002. Botanical and nutritional composition of maize stover, intakes and feed selection by dairy cattle. Livest. Prod. Sci. 71, 87–96. Minson, D.J., 1982. Effects of chemical and physical composition of herbage eaten upon intake. In: Hacker, J.B. (Ed.), Nutritional Limits to Animal Production from Pasture. Commonwealth Agricultural Bureau, Farnharm Royal, UK, pp. 167–182. Mpairwe, D.R., 1998. Integration of forage legumes with cereal crops for improved grain yield, forage production and utilisation for smallholder dairy production systems. PhD thesis, Makerere University, Kampala, Uganda, 241 pp. Mpairwe, D.R., Sabiiti, E.N., Ummuna, N.N., Tegegne, A., Osuji, P., 2002a. Effect of intercropping cereal crops with forage legumes and source of nutrients on cereal grain yield and fodder dry matter yields. Afr. Crop Sci. J. 10 (1), 81–97. Mpairwe, D.R., Sabiiti, E.N., Ummuna, N.N., Tegegne, A., Osuji, P., 2002b. Integration of forage legumes with cereal crops. 1. Effects of supplementation with graded levels of lablab hay on voluntary food intake, digestibility, milk yield and milk composition of crossbred cows fed maize–lablab stover or oats–vetch hay ad libitum. Livest. Prod. Sci. (In press). Phipps, R.H., 1994. Complementary forages for milk production. In: Garnsworthy, P.C., Cole, D.J.A. (Eds.), Recent Advances in Animal Nutrition. University Press, Nottingham, pp. 215–230. Sabiiti, E.N., Mugerwa, J.S., Bareeba, F.B., 1994. Agronomic evaluation of forage legumes for improving native pasture systems in Uganda. In: Ekwamu, A., Ogenga-Latigo, M.W., Bekunda, M.A. (Eds.). African Crop Science Conference Proceedings, Vol. 1. African Crop Society, Kampala, pp. 171– 173. Topps, J.H., 1997. Forage legumes as protein supplements to poor quality diets in the semi-arid tropics. In: Wallace, R.J., LahlouKassi, A. (Eds.), Rumen Ecology Research Planning. Proceedings of a Workshop held at ILRI Addis Ababa, Ethiopia. 13–18 March 1995. Umunna, N.N., Osuji, P.O., Khalili, H., Nsahlai, I.V., Crosse, S., 1995. Comparative feeding value of forages from two cereal legume-based cropping systems for beef production from crossbred (Bos taurus3Bos indicus) steers and subsequent performance of underfed and realimented steers. Anim. Sci. 61, 35–42.
Integration of forage legumes with cereal crops II. Effect of supplementation with lablab hay and incremental levels of wheat bran on voluntary food intake, digestibility, milk yield and milk composition of crossbred cows fed maize–lablab stover or oats–vetch hay ad libitum a, b a ,1 a a D.R. Mpairwe *, E.N. Sabiiti , N.N. Ummuna , A. Tegegne , P. Osuji a
International Livestock Research Institute ( ILRI), Debre Zeit Research Station, P.O. Box 5689, Addis Ababa, Ethiopia b Faculty of Agriculture, Makerere University, P.O. Box 7062, Kampala, Uganda Received 24 April 2001; received in revised form 3 July 2002; accepted 5 July 2002
Abstract This study examined the effects of lablab hay and graded levels of wheat bran supplementation on feed intake, feed degradation characteristics, apparent digestibility, milk yield and milk composition of crossbred cows fed forages from cereal crops 1 legume intercropping (maize / lablab (ML) stover or oats / vetch (OV) hay). Forty eight multiparous crossbred cows arranged in a randomised complete design with eight dietary treatments and six animals per treatment were used in the study. The dietary treatments comprised of either ad libitum ML stover 1 0.5% BW lablab hay or ad libitum OV hay 1 0.9% BW lablab hay, each supplemented with 0, 1.25, 2.50, and 3.75 kg DM of wheat bran. The combination of wheat bran and lablab hay as supplements to cows fed ML stover and OV hay basal diets significantly improved DM digestibility (P , 0.01), which increased (P , 0.001) total DM intake by 21%. DM and OM degradation and the rates of degradation of DM, OM, N and NDF in the rumen were slightly improved by supplementing ML stover or OV hay basal diets with a combination of lablab hay and wheat bran. Supplementation with lablab hay and wheat bran combination increased milk yield by 21% (P , 0.05). Milk yield response to supplementation with lablab hay and wheat bran for the cows consuming ML stover diets was a linear increase (P , 0.001, R 2 5 0.996) with a mean increment of 1.09 kg milk per kg increase of wheat bran DM intake. Milk yield increased by 0.95, 1.3 and 0.95 kg / day for the first, second and third levels of wheat bran supplementation of cows fed ML stover. For OV hay treatments, the relationship between milk yield and increasing levels of wheat bran supplementation was quadratic (P , 0.001; R 2 5 0.990) and the mean response was highest (0.72 kg milk per kg wheat bran intake) at 2.50 kg DM level of wheat bran supplement. Increasing levels of wheat bran supplementation increased milk fat (P , 0.01) and total solids (P , 0.05) for crossbred cows fed ML stover treatments but the increases were not significant for OV hay-based diets. Milk protein concentration was not affected by wheat bran supplementation for both forages. It was concluded from this study that for optimum milk production, cows fed ML stover basal forage should be supplemented with 2.5 kg
*Corresponding author. Present address: Department of Animal Science, Faculty of Agriculture, Makerere University, P.O. Box 7062, Kampala, Uganda. Tel.: 1256-41-532-269. E-mail address: [email protected] (D.R. Mpairwe). 1 Deceased. 0301-6226 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0301-6226( 02 )00178-1
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DM / head / day of wheat bran in addition to 0.5% BW lablab hay while for cows consuming OV hay forage should be supplemented with a combination of 2.5 kg DM / head / day of wheat bran and 0.9% BW lablab hay. The optimum levels of supplementation in this trial were associated with a mean milk yield of 10.94 kg / cow / day for the cows on ML stover basal diet, and 10.84 kg / cow / day milk yield for those on OV hay basal diet. The improved milk yields obtained in the present trial as compared with the results of our previous trial where lablab hay alone was used as a supplement, were attributed to the additive effects of both lablab hay and wheat bran supplements which resulted in improved intake of DM, CP and metabolisable energy. 2002 Elsevier Science B.V. All rights reserved. Keywords: Cereals; Forage legumes; Lablab hay; Wheat bran; Intake; Digestibility; Milk production
1. Introduction Cattle feeding in the tropics and subtropics are often based on natural pastures, hays and / or crop residues, which are generally low in nutritive value and unable to support the higher nutrient requirements of crossbred cows. Cross breeding local cattle (Bos indicus) with exotic species (Bos taurus) has been the policy used in developing countries in the tropics for increasing milk production. Improved feeding of the crossbred cow could be accomplished through the production of better quality forages through intercropping (Khalili et al., 1992, Umunna et al., 1995; Mpairwe, 1998) or appropriate supplementation with locally available by-products. However, the supplement should not have a significantly detrimental effect on intake of the basal food especially where concentrates are scarce and costly relative to forage which are the limiting factors among smallholder farmers in the tropics. Part 1 of this study (Mpairwe et al., 2002b) evaluated the use of forage legume (lablab hay) as a supplement for crossbred (Bos indicus 3 Bos taurus) cows fed maize / lablab (ML) stover or oats / vetch (OV) hay basal forages on diet utilisation and subsequent milk production. The results indicated that supplementation of crossbred cows fed ML stover or OV hay basal forages with increasing levels of lablab hay increased dry matter and crude protein (CP) intake but resulted in moderate levels of animal performance despite the higher increase in CP intake. There was no increased response in milk production of cows given ML stover and OV hay basal forages above supplementation levels of 0.4 and 0.8% BW lablab hay, respectively. The optimum level of lablab hay supplementation that maximised milk production
and reproductive efficiency of crossbred cows was obtained at 0.52 and 0.85% of BW supplementation for ML stover and OV hay basal diets, respectively. The lack of response to higher levels of proteinrich lablab hay supplement was interpreted as resulting from a deficit of dietary energy. It was, therefore, suggested that an intervention with a high energy supplement at the derived optimum levels of lablab hay supplementation may result in higher milk yields. It is important to ensure additivity of the forage legume and wheat bran supplement. Earlier studies (Campling and Lean, 1983) have shown that small amounts of supplementary grains and protein rich concentrates will ensure this. However, it is noteworthy that large amounts of cereal grains are likely to decrease forage intake and result in substitution of concentrate for forage (Campling and Murdoch, 1966). Therefore, the present study was initiated to evaluate the effects of supplementation with a combination of lablab hay and increasing levels of wheat bran, a high energy crop by-product, on feed utilisation and lactation of crossbred cows fed ML stover and OV hay basal diets.
2. Materials and methods
2.1. Animal management and data collection The experiment started at the end of experiment 1 (Mpairwe et al., 2002b). Before the start of the experiment, a total of 60 multiparous crossbred cows were selected from the ILRI—Debre Zeit Research Station dairy herd. The cows were palpated per rectum for ovarian activity and the presence of a corpus luteum. Cows with confirmed presence of a
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corpus luteum were synchronised with estrumate (2 ml per animal) administered intramuscularly, so that they could be inseminated and calve around the same time. The animals were artificially bred at first observed oestrus about 1–5 days after first injection which coincided with 60 days postpartum. After insemination, 48 cows which were confirmed pregnant formed the experimental group. Animal management and data collection were as described by Mpairwe et al. (2002b).
2.2. Feeds, dietary treatments and experimental design Feeds for this experiment (ML stover, OV hay and lablab hay) were produced during the 1996 cropping season and management was as described for experiment 1 (Mpairwe et al., 2002b). Wheat bran was purchased in a single batch from a commercial flour mill. The percentage proportions of cereal and forage legumes in the intercropped feeds used in this study were 67% maize and 33% lablab (i.e. 2:1 ratio) for ML stover, while OV hay comprised 70% oats and 30% vetch (2.3:1 ratio). The experiment was a randomized complete block design with eight dietary treatments and six animals per treatment. The dietary treatments comprised of either ad libitum ML stover 1 0.5% BW lablab hay or ad libitum OV hay 1 0.9% BW lablab hay, each supplemented with 0, 1.25, 2.50, and 3.75 kg DM of wheat bran. The optimum levels of lablab hay supplementation of cows fed ML stover (0.5% BW) and for cows on OV hay (0.9% BW) were determined in experiment 1 (Mpairwe et al., 2002b). The experiment started 2 months before calving and ended 120 days (4 months) after calving for each experimental cow. Body weight changes of the cows and DM of the feeds on offer and refusals were monitored fortnightly and adjustments of the supplement on offer made accordingly. The rest of the experimental procedures were as described in experiment 1.
2.3. Feed degradation characteristics Feed degradation characteristics of intercropped feeds (ML stover and OV hay), supplements (lablab hay and wheat bran) and sululta hay for comparison were established using nylon bags (Mehrez and
215
Orskov, 1977). Six rumen fistulated crossbred (Bos taurus 3 Bos indicus) steers (mean live body weight 330637 kg), housed and fed individually were used. The trial was a completely randomized block design with two dietary treatments and three replications. The animals were blocked by weight into two blocks and allotted randomly to two dietary treatments: ML stover supplemented with 0.5% BW lablab hay and 2.8 kg DM wheat bran and OV hay supplemented with 0.9% BW lablab hay and 2.8 kg DM wheat bran. The level of 2.8 kg DM wheat bran supplementation in this trial was the optimum level which was determined with crossbred cows fed ML stover10.5% BW lablab hay and OV hay10.9% BW lablab hay. The animals were adapted for 14 days followed by 6 days for nylon bag incubation. The feeds (ML stover, OV hay, Sululta hay, lablab hay and wheat bran) were ground to pass through a 2-mm screen and DM, OM, N and NDF degradabilities studied (Mehrez and Orskov, 1977). Bags of Sululta and lablab hays were incubated in all the animals together with either ML stover bags for the animals consuming ML basal diet or OV hay bags for animals fed OV hay basal diet. Wheat bran bags were incubated in the wheat bran supplemented animals only. The procedure for nylon bag incubation and processing were as described in experiment 1.
3. Results
3.1. Chemical composition and degradation characteristics of the feeds The chemical composition of the feeds is presented in Table 1. Organic matter (OM) concentrations were similar among the forage feedstuffs and was highest in wheat bran. The two basal forages did not vary much in their NDF concentrations but OV hay had higher CP concentration than ML stover. Mineral concentrations were similar in both basal forages and were higher than the estimated requirements of rations for dairy cattle (experiment 1) indicating that concentrations of the essential minerals for dairy cows were not limiting in the two basal forages. The level of CP in ML stover (8.2% CP) was lower while that in OV hay (11% CP) was
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Table 1 Chemical composition (g / kg DM) of experimental feeds
Dry matter (g / kg) Organic matter Neutral detergent fibre (NDF) NDF–Nitrogen (g / kg NDF) Acid detergent fibre Acid detergent lignin Crude protein (N 36.25) Minerals (g / kg DM) Calcium Phosphorus Magnesium Potassium a
Maize / lablab stover
Oats / vetch hay
Lablab hay
Offer
Refusal
Offer
Refusal
Offer
Refusal
888 883 593 2.82 381 45.4 81.9
852 909 635 ND ND ND 48.7
899 885 602 3.67 390 49.5 109.9
858 899 722 ND ND ND 54.4
901 885 412 2.62 346 60.7 148.8
885 884 538 ND ND ND 86.9
8.1 3.9 2.7 22.8
ND ND ND ND
6.4 5.5 2.0 31.9
ND ND ND ND
17.1 5.4 3.8 29.7
ND ND ND ND
Wheat bran Offer
Grass a (sululta) hay
868 946 487 5.76 134 27.7 161.2
920 888 624 ND ND ND 61.9
1.7 11.9 5.2 13.1
ND ND ND ND
Grass hay was used in the degradability studies. ND, not determined.
within the range of 11–12% CP required for moderate levels of ruminant production (ARC, 1980). However, these CP concentrations in the two basal forages were higher than the limiting level (6–8% CP) below which appetite and forage intake are depressed (Minson, 1982; Forbes, 1986). The supplements (lablab hay and wheat bran) had the highest CP and lowest NDF concentrations relative to the basal diets (ML stover and OV hay). Mineral concentrations were also higher in the supplements than in the basal forages. Lablab hay had higher calcium concentration (17.1 g / kg) than wheat bran (1.7 g / kg) but the concentration of phosphorous was higher in wheat bran (11.9 g / kg) than in lablab hay (5.4 g / kg). Crude protein concentrations were higher while the NDF concentrations were lower for the two basal forages than that in grass (Sululta) hay; thus showing the superiority of intercropped feeds over the commonly used pasture hays. Rumen degradation characteristics of the feedstuffs are presented in Table 2. Potential DM and OM degradabilities were significantly (P,0.05) higher in wheat bran than in lablab hay but the effective degradabilities were similar. However, lablab hay had higher DM and OM degradation rate (P,0.001) than wheat bran. The potential and effective DM, OM, N and NDF degradabilities were similar for ML stover and OV hay basal diets and did not differ significantly (P.0.05) from that of grass hay. DM, OM and NDF degradation rates did not differ between the basal diets, wheat bran and the
grass hay but wheat bran had faster N degradation rate (P,0.001 than the basal diets.
3.2. Nutrient intake and diet apparent digestibility The results of the effects of lablab hay and wheat bran supplementation of cows fed ML stover or OV hay basal diets on intake and diet apparent digestibility are presented in Table 3. Dry matter intake of the basal diet tended to be higher for ML stover treatments than for cows on OV hay treatments. Total DM intake for the control treatments was significantly (P,0.01) higher for cows fed OV hay10.9% BW lablab hay than for cows consuming ML stover10.5% BW lablab hay. Wheat bran supplementation did not affect ML stover intake at 1.25 kg DM level of supplement but higher levels of wheat bran supplementation significantly (P,0.05) decreased ML stover intake. However, there was no significant difference in basal diet intake between the control treatment and supplemented ML stover treatments up to the level of 2.50 kg DM wheat bran. Maize–lablab stover intake was significantly (P, 0.01) reduced at the highest level of wheat bran (3.75 kg DM). For OV hay treatments, increasing levels of wheat bran supplementation significantly (P,0.001) decreased OV hay DM intake. Total DM intake for the control treatment was significantly (P,0.001) lower than for the wheat bran supplemented ML stover treatments; and it increased with increasing levels of wheat bran supple-
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Table 2 Degradation constants (g / kg DM) of dry matter (DM), organic matter (OM), nitrogen (N) and neutral detergent fibre (NDF) of experimental feeds
DM
OM
N
NDF
Maize/lablab stover (1)
Oats/vetch hay (2)
Lablab hay (3)
Wheat bran (4)
Sululta hay (5)
S.E.D. (n54)
Significance level (P) 1&2 vs. 5
1&2 vs. 3
1&2 vs. 4
3 vs. 4
Solubility a b PD ED TL c
293 220 526 746 539 24.3 0.039
302 251 468 719 525 20.6 0.037
419 295 489 784 693 23.1 0.102
474 300 544 844 693 211.3 0.047
213 156 502 658 425 21.1 0.030
19.98 20.02 11.31 12.22 2.63 0.01
0.001 ns 0.001 0.001 ns ns
0.001 ns 0.001 0.001 ns 0.001
0.001 0.05 0.001 0.001 0.001 ns
ns 0.01 0.001 ns 0.01 0.001
Solubility a b PD ED TL c
232 211 537 748 512 20.3 0.037
270 186 531 717 501 21.7 0.037
382 280 489 769 670 22.8 0.100
477 302 543 845 681 213.8 0.040
166 146 492 638 397 1.2 0.030
19.29 20.54 11.75 12.97 2.47 0.01
0.01 0.05 0.001 0.001 ns ns
0.001 0.01 0.001 0.001 ns 0.001
0.001 ns 0.001 0.001 0.001 ns
ns 0.01 0.001 ns 0.001 0.001
Solubility a b PD ED TL c
466 300 480 780 698 25.8 0.099
431 274 483 757 680 22.9 0.107
532 244 676 920 849 23.0 0.153
606 240 698 938 889 24.9 0.227
399 107 408 515 440 22.4 0.033
20.14 28.83 24.77 13.31 2.11 0.038
0.001 0.01 0.001 0.001 ns 0.05
0.05 0.001 0.001 0.001 ns ns
0.01 0.001 0.001 0.001 ns 0.001
ns ns ns 0.001 ns 0.05
Solubility a b PD ED TL c
54 84 596 680 384 4.1 0.037
82 104 550 654 376 4.8 0.035
154 191 426 617 462 0.2 0.068
110 202 569 771 421 20.1 0.029
58 69 547 616 325 5.0 0.029
25.06 25.21 16.93 17.90 1.77 0.008
ns ns 0.001 0.001 ns ns
0.001 0.001 0.001 0.001 0.01 0.001
0.001 ns 0.001 0.01 0.01 ns
ns 0.001 0.001 0.01 ns 0.001
a5zero time intercept; b5insoluble but potentially (slowly) degradable component; c5the rate of degradation of b component; PD5(a 1 b), potential degradability (g / kg); TL5lagtime (h); ED5effective degradability (g / kg) at outflow rate of 0.03; ns5not significant; S.E.D.5standard error of difference.
mentation. However, there were no significant differences in total DM intake among the wheat bran supplemented treatments. Total DM intake for the control treatment of OV hay-based treatments was not different from the wheat bran supplemented treatments but among the supplemented treatments, it significantly (P,0.01) increased with increasing levels of wheat bran. Substitution rates (SR) were calculated as the ratio of the difference in intake of ML stover or OV hay between the control treatment and the supplemented treatment to the quantity of wheat bran supplement. SR were 20.08, 0.25 and 0.43 (i.e. 21.4, 8.5 and
22.5%) for ML stover-based diets and 0.83, 0.66, 0.54 (i.e. 15, 25, and 31.5%) for OV hay based diets at 1.25, 2.50 and 3.75 kg DM levels of wheat bran supplementation, respectively. This indicated that wheat bran supplementation did not substitute the basal diet up to the level of 1.25 kg DM in ML stover based diets but substituted OV hay at all levels of supplementation. Intake of organic matter (OMI) and digestible organic matter (DOM) for wheat bran supplemented treatments were significantly higher (P,0.01) for ML stover diets and (P,0.001) for OV hay diets than the control treatments. Increasing levels of
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Table 3 Mean daily nutrient intake and apparent digestibility by crossbred cows fed ad libitum maize / lablab10.5% BW lablab hay (ML1LB) or oats / vetch hay10.9% BW lablab hay supplemented with graded levels of wheat bran
Basal diets:
Treatments
S.E.D.
Significance (P)
ML stover10.5% BW lablab (ML) OV hay10.9% BW lablab (OV)
(n56)
Treatment
ML vs. OV
ML vs. SP
OV vs. SP
Wheat bran (kg DM): Dry matter intake (kg/day) Basal diet Lablab hay Wheat bran Total DM digestibility (g/kg) Organic matter OMI (kg/day) DOMI (kg/day) OMD (g/kg) DOMD (g/kg) CP intake (kg/day) Digestibility (g/kg) NDF intake (kg/day) Digestibilty (g/kg) Metabolisable energy MEF (MJ/kg DM) Intake (MJ/head/day)
0
7.1 2.2
1.25
2.50
3.75
9.3 658
7.2 2.1 1.2 10.5 683
6.5 2.2 2.4 11.2 705
5.5 2.2 3.7 11.4 678
8.1 6.4 677 591 1.02 676 4.95 613
9.2 7.4 701 619 1.20 713 5.56 627
9.9 8.2 725 645 1.36 743 5.83 654
10.2 8.0 700 627 1.48 729 5.80 590
–
0
6.3 4.1
1.25
2.50
3.75
4.7 4.1 2.4 11.2 688
4.3 4.1 3.7 12.1 700
0.44 – – 0.46 16.46
0.001
ns
ns
0.001
– 10.4 637
5.3 4.1 1.2 10.6 672
0.001 0.01
0.01 ns
0.001 0.05
ns 0.01
9.3 7.5 695 617 1.53 727 5.07 532
9.4 7.8 717 632 1.58 749 5.05 587
10.0 8.1 714 639 1.71 772 5.23 599
10.9 0.40 8.9 0.50 726 14.33 653 12.68 1.93 0.04 787 7.59 5.56 0.29 595 33.00
0.001 0.001 0.01 0.001 0.001 0.001 ns ns
0.01 0.01 0.01 0.01 0.001 0.001 ns ns
0.001 0.001 0.01 0.001 0.001 0.001 0.01 ns
0.05 ns ns ns 0.001 0.001 ns ns
0.001 0.001
0.01 0.01
0.001 0.001
ns ns
9.10 9.53 9.93 9.65 9.50 9.72 9.83 10.1 85.6 100.7 111.7 110.5 102.2 105.3 111.5 123.6
0.19 6.79
OMD5digestibility of the organic matter; DOMD5digestible organic matter in the dry matter; MEF5metabolisable energy of feed (MEF50.153DOMD%); ML vs. SP5(ML10.5% Lablab) vs. (ML10.5% BW Lablab1wheat bran); OV vs. SP5(OV10.9% BW Lablab) vs. (OV10.9% BW Lablab1 wheat bran); ns5not significant; S.E.D.5standard error of difference.
wheat bran led to increased OMI and DOMI but the increases were not significant for OV hay based diets. Diet apparent DM digestibility (DMD) and organic matter (OMD) were improved by wheat bran supplementation when compared with ML stover1 0.5% BW and OV hay10.9% BW lablab hay treatments. However, there were no significant differences in DMD among the wheat bran supplemented diets. Digestible organic matter in the dry matter (DOMD) for OV hay10.9% BW lablab hay was higher than that of ML stover10.5% BW lablab hay. Supplementation improved DOMD but there was no significant difference among the supplemented treatments. Treatment effects on crude protein intake (CPI) were highly significant (P,0.001) (Table 3). CPI with ML stover10.5% BW lablab hay was lower than that of OV hay10.9% BW lablab hay. CP intake of wheat bran supplemented treatments was significantly (P,0.001) higher than the control treatments (ML stover10.5% BW lablab hay and
OV hay10.9% BW lablab hay). NDF intake and digestibility were similar in both ML10.5% BW lablab hay and OV hay10.9% lablab hay. However, supplementation with wheat bran led to improved NDF intake for cows consuming ML stover diets (P,0.01) while for OV hay the increase was not significant. NDF digestibility was not affected by the different dietary treatments. Metabolisable energy of the feed (MEF) for ML stover10.5% BW lablab hay was lower than that for OV hay10.9% BW lablab hay. Wheat bran supplementation significantly (P,0.001) increased MEF from 9.10 to 9.93 MJ / kg DM for ML stover-based diets and from 9.50 to 10.1 MJ / kg DM for OV hay diets but the increase was not significant for OV hay-based diets. Wheat bran supplementation increased metabolisable energy intake (MEI) from 85.6 to 110.5 and from 102.2 to 123.6 MJ / head / day for ML stover and OV hay treatments, respectively; but there were no significant differences among OV hay treatments. The mean responses to increased ME
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intake (estimated according to MAFF, 1987) were 0.038 and 0.058 kg milk per MJ MEI for ML stoverand OV hay-based diets, respectively.
3.3. Mineral intake and Ca: P ratio The effect of wheat bran supplementation of cows fed ML stover or OV hay basal forages at optimum levels of lablab hay on mineral intakes (Ca, P, Mg and K) and the calcium to phosphorous (Ca:P) ratios are presented in Table 4. Chemical composition of the feeds (Table 1) showed that the concentrations of Ca, P, Mg and K differed between ML stover, OV hay, lablab hay and wheat bran. Consequently, treatment effects on mineral intake and Ca:P ratio were highly significant (P,0.001). Ca intake from ML stover10.5% BW lablab hay based diets was significantly (P,0.001) lower than that from OV hay10.9% BW lablab hay diets. Mg intake was similar for both control diets while increasing levels of wheat bran supplementation significantly (P, 0.001) increased Mg intake in both forage diets but there were no significant differences among the
219
wheat bran supplemented treatments. ML stoverbased diets promoted significantly (P,0.001) lower K intake than OV hay treatments but there were no significant treatment differences within each forage type. Calcium to phosphorus ratio was significantly (P, 0.001) higher for the control treatments than the wheat bran supplemented treatments. Ca:P ratios of ML stover10.5% BW lablab hay (2.41) and OV hay10.9% BW lablab hay (2.04) control treatments were similar to the ratios obtained in experiment 1, thus, indicating the repeatability of the results. However, supplementation with wheat bran significantly (P,0.001) reduced the Ca:P ratios in both forage diets but were within the recommended range 1–2:1 for cattle (McDonald et al., 1987).
3.4. Milk yield and milk composition The results for the effects of lablab hay and wheat bran supplementation on milk yield and milk composition are presented in Table 5. There were no significant (P.0.05) differences in milk yield be-
Table 4 Mineral intake a by crossbred cows fed ad libitum maize / lablab stover10.5% BW lablab hay (ML1LB) or oats / vetch hay10.9% BW lablab hay (OV1LB) supplemented with graded levels of wheat bran Treatments Basal diet
Mean mineral intake (g / head / day) Wheat bran level (kg DM)
Calcium
Phosphorus
Magnesium
Potassium
Ca:P
ML1LB T1 T2 T3 T4
0 1.25 2.50 3.75
94 96 95 88
39 54 66 77
27 34 39 43
226 242 246 238
2.41 1.79 1.43 1.12
OV1LB T5 T6 T7 T8
0 1.25 2.50 3.75
115 106 103 105
58 66 77 90
29 32 37 44
327 307 302 308
2.04 1.62 1.34 1.16
S.E.D. (n56) Significance Treatment T1 vs. T5 T1 vs. (T21T31T4) T5 vs. (T61T71T8) (T21T31T4) vs. (T61T71T8) a
3.62
2.40
1.05
0.001 0.001
0.001 0.001 0.001 0.001 0.001
0.001 ns 0.001 0.001 ns
ns 0.05 0.001
13.87 0.001 0.001 ns ns 0.001
0.03 0.001 0.001 0.001 0.001 0.001
Mineral intake from the experimental forages only (in addition, the animals were provided with mineral blocks). ns5not significant; S.E.D.5standard error of difference.
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Table 5 Mean daily milk production characteristics and mean body weight changes of crossbred cows fed ad libitum maize / lablab10.5% BW lablab hay (ML1LB) or ad libitum oats / vetch hay10.9% BW lablab hay (OV1LB) supplemented with graded levels of wheat bran Treatments Basal diets: Wheat bran (kg DM): Milk production Milk yield (kg/day) Fat yield (g/day) Protein yield (g/day) Total solids (g/day)
ML stover10.5% BW lablab (ML) 0
1.25
2.50
3.75
OV hay10.9% BW lablab (OV) 0
1.25
2.50
S.E.D.
Significance (P)
(n56)
Treatment
ML vs. OV
ML vs. SP
OV vs. SP
0.05 0.001 0.001 0.001
ns ns ns ns
0.01 0.001 0.01 0.001
0.05 0.01 0.01 0.01
3.75
8.69 9.64 10.94 11.89 9.04 9.89 10.84 11.15 0.85 360 428 522 564 409 471 549 567 36.16 256 294 340 366 281 318 354 360 24.98 1043 1211 1425 1442 1130 1294 1439 1435 100.07
Milk composition (g/kg) Fat Protein Total solids
43.2 30.5 125.1
44.6 30.7 126.1
48.8 31.5 131.7
50.7 32.5 128.6
45.8 31.3 125.6
47.9 32.1 131.0
51.4 33.0 133.6
52.3 33.5 132.6
2.53 0.95 3.07
0.01 0.05 0.05
ns ns ns
0.01 ns 0.05
ns ns ns
Body weight changes (calving to 120 days) Calving weight (kg) LW at 120 days (kg) Mean weight change (kg) Mean weight gain (g/day)
434 408 23.8 29.8
451 403 25.83 227.3
463 418 1.17 210.2
463 426 27.1 6.9
445 419 21.2 18.9
446 389 24.6 215.5
441 382 24.0 218.9
456 438 24.5 223.5
12.97 13.97 11.82 48.63
0.05 0.05 ns ns
ns ns ns ns
0.01 ns ns ns
ns 0.05 ns ns
ML vs. SP5(ML10.5% lablab) vs. (ML10.5% BW lablab1wheat bran); OV vs. SP5(OV10.9% BW lablab) vs. (OV10.9% BW lablab1 wheat bran); LW5live weight; ns5not significant; S.E.D.5standard error of difference.
tween the control treatments although animals on OV hay10.9% BW lablab hay tended to have higher milk yield than those on ML stover10.5% BW lablab hay. For ML stover-based treatments, wheat bran supplementation significantly (P,0.01) increased milk yield from 8.69 to 11.89 kg / head / day while for OV hay-based diets there was also a significant (P,0.05) increase in milk yield from 9.04 to 11.15 kg / head / day. The response in milk yield for ML stover treatments was a linear increase (P,0.001, R 2 50.996), resulting in a mean increment of 1.09 kg milk per kg increase in the wheat bran DM intake (Fig. 1). Milk yield increased by 0.95, 1.3 and 0.95 kg / day for the first, second and third levels of wheat bran supplementation of cows fed ML stover. The corresponding increases in milk yields per kg of wheat bran intake as compared to the control diet (T1) were 0.76, 0.90 and 0.85 kg / day at 1.25, 2.50 and 3.75 kg DM levels of wheat bran, respectively. This indicated that milk yield of crossbred cows fed ML stover basal forage was optimised when supplemented with a combination of 0.5% BW lablab hay and 2.50 kg DM wheat bran. For OV hay treatments, although the linear re-
Fig. 1. Milk yield regression response curve for crossbred cows fed ML stover10.5% BW lablab hay supplemented with graded levels of wheat bran.
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sponse was significant (P,0.05, R 2 50.963), there was a strong quadratic relationship (P,0.001, R 2 5 0.990) between milk yield and increasing levels of wheat bran supplementation (Fig. 2). Milk yield increased by 0.85, 0.95 and 0.31 kg / head / day and the corresponding increases in milk yields per kg wheat bran intake compared with the control diet were 0.68, 0.72 and 0.56 kg / day at 1.25, 2.50 and 3.75 kg DM levels of wheat bran supplementation, respectively. The mean response to wheat bran supplementation was highest at the second increment of supplement (0.72 kg milk per kg wheat bran intake) as compared with responses of 0.68 and 0.56 to the first and third increments, respectively. The results, thus indicated that for crossbred cows fed OV hay basal forage, milk yield was optimised when the cows were supplemented with a combination of 0.9% BW lablab hay and 2.50 kg DM wheat bran per cow each day. Treatment effects were significant for milk fat, protein and total solids (Table 5). However, there were no significant differences in any of the milk
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components studied between the control treatments (T1 vs. T5). Increasing levels of wheat bran supplementation significantly increased the concentrations of milk fat (P,0.01) and total solids (P,0.05) for crossbred cows fed ML stover treatments. Similarly, for OV hay-based diets, the concentrations of milk fat and total solids increased with increasing levels of wheat bran supplementation but the differences were not significant (P.0.05). Milk protein concentration was not affected by wheat bran supplementation. Milk components (fat, protein and total solids) yield followed a similar trend as milk yield. There were no significant differences in milk fat, protein and total solids yield between the control diets (T1 and T5). Increasing levels of wheat bran supplementation significantly increased milk fat, protein and total solids yield (P,0.001) for cows fed ML stover treatments and (P,0.01) for cows on OV hay treatments.
4. Discussion
4.1. Chemical composition and degradability of the feeds
Fig. 2. Milk yield regression response curve for crossbred cows fed OV hay10.9% BW lablab hay supplemented with graded levels of wheat bran.
The quality of ML stover used in this experiment was lower than that used in our previous trial (Mpairwe et al., 2002b) and was attributed to the unexpected rains of November 1996 up to January 1997 that occurred during the harvesting and storage period. During the drying process, some leaves, especially of the lablab component in the harvested material, became rotten due to excessive moisture while others shattered because the maize component in the mixture took longer to dry. As a result the proportion of lablab in ML stover was lower than expected and hence the lower CP concentration when compared with the ML stover used in experiment 1. The better quality of OV hay used in the present trial was attributed to the well-distributed rains of June to September 1996 and to the subsequent dry conditions in October. Therefore, the OV hay, which was harvested at the beginning of October, was dried and stored in a favourable good weather for haymaking. Consequently, the proportion of vetch in the OV hay was higher than that of the OV hay used in experiment 1 and hence the higher CP concentration.
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4.2. Nutrient intake and diet apparent digestibility The differences in DM intake between the ML stover and OV hay-based treatments were attributed to the differences in quality of the two basal forages. It has been noted that if the basal diet has a low nitrogen content, the addition of a forage legume will increase the nitrogen content of the total diet. This is likely to increase feed intake and the rate of degradation of the basal diet in the rumen (Topps, 1997). This, therefore, explains why supplementation increased total DM intake for ML stover-based treatments while it did not affect total DM intake for OV hay-based treatments when compared with the control treatments. The addition of lablab hay into ML stover (which had low CP content) treatments increased total DMI as opposed to OV hay which was of better quality (high CP) when compared with the control treatments. The improved total dry matter intake observed in this experiment was associated with the improved DMD and OMD which in turn was attributed to the increased rates of DM and OM degradation (Mpairwe, 1998) deriving from supplementation with wheat bran. In addition, from the results of Mpairwe (1998), the reduced total mean retention time with increasing levels of wheat bran could have contributed to the improved total DM and OM intake. On the other hand, the increased CPI experienced in this study was attributed to the intake of both lablab hay and wheat bran, which were high in CP. When compared with calculated values, the CP intakes of the cows in this trial were adequate for estimated CP intake (MAFF, 1987) requirements for maintenance and milk production (excluding live weight changes) except for the control diet of ML stover-based diets, which indicated a deficit of 273 g CPI. Supplementing cows consuming ML stover10.5% BW lablab hay with 2.5 kg DM wheat bran and for cows on OV hay10.9% BW lablab hay with 1.25 kg DM increased total DM intake without significant substitution of the basal diet. Consequently, total OM intake increased by the amount of supplement given. However, when wheat bran was given at a higher level (3.75 kg DM / day) the DMI of ML stover was reduced by 1.6 kg (22.5%) and the DMI of OV hay was reduced by 2.0 kg (31.8%), thus, indicating that substitution of the basal diet by wheat bran was
greater for OV hay than for ML stover. Campling and Murdoch (1966) reported that when concentrates were given to cows the substitution rate tended to be greatest with the hays of highest digestibility. Similarly, Faverdin et al. (1991) observed that substitution rate was greater with silage that had an energy value superior to that of hay. Therefore, the better nutritive value (higher CP content and ME) of OV hay forage could have contributed to the higher substitution rates by wheat bran supplementation than was observed in ML stover. The substitution rates obtained in this experiment were lower than the SR obtained by Mpairwe et al. (2002b) indicating that supplementing cows fed ML stover or OV hay with a combination of lablab hay and wheat bran reduced the substitution effects which were experienced when lablab hay alone was used as a supplement. The estimated MEI requirements for maintenance and milk production (excluding body weight changes) of a lactating dairy cow weighing 400 kg and producing 10 kg / day milk of 4.8% butter fat) was 106 MJ / head / day (MAFF, 1987). For the control treatments and at the lowest level of wheat bran (1.25 kg DM) supplementation in both forages, the results indicated a deficit in MEI that was highly significant (P,0.001) for ML10.5% BW lablab hay diet which had a negative MEI of 20.4 MJ / head / day. The lower MEI in the control treatment for ML stover-based diets as compared to the wheat bran supplemented treatments in this experiment was attributed to the lower total DM and OM intakes (Table 3). However, wheat bran supplementation of cows fed ML stover10.5% BW lablab hay or OV hay10.9% BW lablab hay at the level equal to and higher than 2.50 kg DM of wheat bran met the estimated ME requirements of the cows. Compared with the results in experiment 1 (Mpairwe et al., 2002b), the mean ME intake (110.6 MJ / head / day) for the wheat bran supplemented treatments in addition to the optimum level of lablab hay was similar to the mean ME intake (108.1 MJ / head / day) obtained when lablab hay alone was used as a supplement. The mean responses to increased ME intake (estimated according to MAFF, 1987) were 0.038 and 0.058 kg milk per MJ MEI for ML stover- and OV hay-based diets, respectively. These values were higher than the response of 0.037 and 0.044 kg milk per MJ ME for ML and OV diets,
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respectively, in response to wheat-middlings (Khalili et al., 1994). The values, however, were lower than the response of 0.14 kg milk per MJ change in intake of cows producing 20 kg / day (Broster and Thomas, 1981). The improved metabolisable energy intake in the present trial was associated with improved OMI and DOMD as a result of lablab hay and increasing levels of wheat bran in the diets.
4.3. Mineral intake The lower Ca intake for ML stover10.5% BW lablab hay based diets than for OV hay10.9% lablab hay diets was attributed mainly to the difference in the amount of lablab hay intake. The amount of lablab hay consumed in the OV hay based diets was higher than that consumed by animals fed ML stover diets (Table 1). Increasing levels of wheat bran supplementation tended to decrease Ca intake while P intake increased with increasing levels of wheat bran supplementation in both forages. The decrease in Ca intake was associated with increase in wheat bran intake which had very low Ca concentration while the increased P intake was attributed to the intake of both lablab hay and increasing levels of wheat bran which both had substantial quantities of P (Table 1). Supplementation with wheat bran reduced the Ca:P for both ML stover and OV hay based diets and the values were within the recommended range of 1–2:1 for cattle (McDonald et al., 1987). The results of this experiment therefore revealed the advantage of supplementing intercropped feeds with a combination of lablab hay and wheat bran. The high levels of Ca in lablab hay were probably counterbalanced by the high levels of P in wheat bran and thus optimising the Ca:P ratio. Furthermore, the results in this study indicated that the intakes of Ca and P were adequate for estimated (MAFF, 1987) mineral requirements (36.6 and 27.4 g / head / day for Ca and P, respectively) of a dairy cow of mean live weight 400 kg, producing 8–13 kg milk of 4% butter fat. The combination of lablab hay and wheat bran supplements, thus satisfied the essential mineral requirements for cattle especially Ca and P which are the most limiting minerals for milk production and often encountered in high grade cows fed low quality forages.
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4.4. Milk yield and milk composition The tendency for the animals on OV hay10.9% BW lablab hay to have higher milk yield than those on ML stover10.5% BW lablab hay was associated with the higher CP concentration of OV hay (Table 1) and the higher amount of lablab hay offered. This resulted in higher CP intake and CP digestibility of cows fed OV10.9% BW lablab hay (Table 3) than the cows on ML stover10.5% BW lablab hay. The average daily milk yield for each of the 17-week lactation period of the trial (Fig. 3) clearly showed that milk production was always higher for crossbred cows receiving wheat bran supplementation than for the cows on the control treatments. This showed that additional wheat bran supplementation added to lablab hay increased milk yield of crossbred cows fed ML stover or OV hay basal diets. The increased milk fat with wheat bran supplementation may have been due to increasing concentrations of rumen butyrate (Mpairwe, 1998). Previous studies have shown increased milk fat to result from increased rumen butyrate (Bowman and Huber, 1967; Broster et al., 1970). The trend toward increased milk protein concentrations could be attributed to the higher levels of CP intake with increasing levels of wheat bran supplementation which has been reported to increase milk yield and milk protein concentration (DePeters and Cant, 1992; Phipps, 1994). The higher milk production of crossbred cows fed ML stover and OV hay basal diets supplemented with lablab hay and wheat bran than in the previous experiment when the crossbred cows fed the same basal forages were supplemented with lablab hay only was explained by the greater degradabilities of DM, OM, N and NDF reported by Mpairwe (1998). In addition, the combination of lablab hay and wheat bran supplementation had higher values of degradation rate constants (c value) than when the two forages were fed to crossbred cows supplemented with lablab hay alone. The differences between the two experiments suggest that probably there was more of both energy and nitrogen available for the rumen microbes when the cows fed ML stover and OV hay basal forages were supplemented with a combination of lablab hay and wheat bran than when supplemented with lablab hay alone. This was evidenced by the results for crude protein intake (CPI)
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Fig. 3. Lactation curves for crossbred cows fed maize / lablab stover10.5% BW lablab hay (ML1LB) or oats / vetch hay10.9% BW lablab hay (OV1LB) basal forages supplemented with graded levels of wheat bran.
and metabolisable energy intake (MEI) (Table 3). Crude protein and metabolisable energy intakes of the wheat bran supplemented treatments were above the estimated CPI (1.29 kg) and MEI (106 MJ / head / day) requirements for maintenance and milk production of a dairy cow weighing 400 kg, producing 8 kg / day milk of 4% butter fat. Since wheat bran provided additional crude protein and energy (Table 1) for the crossbred cows it was difficult to separate the effect of increased protein and / or energy supply on feed intake, apparent digestibility and milk yield. Therefore, the results of this trial could not explain whether the lower milk yields obtained with lablab hay supplementation (experiment 1) were as a result of inadequate energy supply to the cows during lactation. Instead, the improved milk yields obtained in the present trial as compared with the results of experiment 1 were attributed to the additive effects of improved feed intake, CP intake and ME intake from both lablab hay and wheat bran supplements. Therefore, it was suggested that research involving the use of additional energy supplements from non-proteinaceous feed sources like molasses should be conducted to establish the lower milk yields experienced when the crossbred cows fed ML stover and OV hay basal forages were supplemented with lablab hay alone. The present study showed that the mean milk yield response to wheat bran supplementation was highest at the second increment of wheat bran supplement (0.90 kg for ML and 0.72 kg for OV hay milk yield per kg wheat bran intake). This indicated that milk
yield of crossbred cows fed ML stover and OV hay basal forages was optimised when supplemented with a combination of either 0.5% BW lablab hay for ML stover or 0.9% BW lablab hay for OV hay with 2.50 kg DM wheat bran. At the current farm gate price of milk (US$0.286 per kg) in Ethiopia, the responses in milk yield per kg DM wheat bran fed were US$0.217, 0.257 and 0.243 for the first, second and third increments of wheat bran, respectively, in ML stover-based diets. For OV hay-based diets the corresponding responses in milk yield to wheat bran supplementation were US$0.195, 0.206 and 0.160 per kg DM wheat bran fed. The current cost of wheat bran in Debre Zeit, Ethiopia is about US$0.071 / kg. Based on the treatment milk yield responses per kg wheat bran and the corresponding monetary values, it was recommended that for optimum milk yields, crossbred cows fed ML stover10.5% BW lablab hay or OV hay10.9% BW lablab hay should be supplemented with additional 2.50 kg DM wheat bran. However, there is need for more research to determine suitable economic optimum levels for smallholder that should be adopted in relation to local quantities and qualities of the basal forages and lablab that can be expected. The optimum levels of supplementation in this trial were associated with a mean milk yield of 10.94 kg / cow / day, for the cows on ML stover basal diet; and 10.84 kg / cow / day milk yield, for those on OV hay basal diet. At these optimum levels of lablab hay and wheat bran supplementation when compared with the optimum level where lablab hay supplement
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alone in our previous trial (Mpairwe et al., 2002b), milk yield increased by 24.7% (8.77 vs. 10.94 kg / head / day) for ML based diets and 12% (9.68 vs. 10.84 kg / head / day) for cross bred cows fed OV hay diets. These improvements were attributed to the additive effects of improved intake of feed DM, CP and ME from both lablab hay and wheat bran supplements. Differences in the nutritional value of the two basal forages were associated with the better quality of OV hay, which had higher CP content than ML stover (Table 1). OV hay was harvested at milk stage and hence had higher CP content than ML stover, which was harvested at full maturity of the cereal component in the mixture. As such, the difference in the response of the cows was attributed to the difference in the nutritional value of the two forages whereby supplementation benefited more the low quality ML forage than OV hay.
4.5. Socio-economic implications of the study There is need to develop feeding systems based on locally available feed resources in order to improve production in smallholder dairy farming systems in the tropics. In Eastern and southern Africa, cereal crop residues especially maize stovers are readily available as a by-product of maize grain production and most farmers collect and store it for dry season feeding. Smallholder farmers grow cereal crops especially maize although not in very large amounts owing to the small land size per household. Methu et al. (2002) reported that these smallholders produce an average of 1.8 tonnes of stover per household per year. This is substantial amount given that the average herd size for smallholders is normally two milking cows and two calves and that maize stover is mainly used as a dry season feed. Lablab grows well in mixtures with maize or soghum and can be interplanted into banana and coffee plantations and whatever space available on farm. It produces herbage high in DM and CP and improves the quality of the stovers (Mpairwe et al., 2002a). Moreover, lablab is widespread throughout the tropics especially in Africa as a food crop (Gohl, 1975). There is increasing emphasis on the use of lablab and is being promoted as a fodder crop for supplementing low quality forages in intensive smallholder dairy production systems in Eastern and Southern Africa (Kiflewahid and Mosimanyama, 1987; Sabiiti et al.,
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1994; Mpairwe, 1998). Agro-industrial crop by products like wheat bran are readily available from flour mills within the region since maize and wheat flour are the major stable foodstuffs in the developing tropics. Therefore, the technology of utilising lablab to improve the quality of cereal stovers and as a supplement in combination with wheat bran can be an effective strategy to improve intake and milk production of crossbred cows in smallholder farming systems.
5. Conclusions It was concluded that although forages resulting from cereal and forage legume intercropping are of superior quality when compared with their respective cereal crop residues, there is need for supplementation when they are fed to crossbred cows for optimum milk production. In smallholder dairy production systems in the tropics where resources are scarce, supplementation could be achieved by utilising forage legumes (lablab hay) and locally available agro-industrial crop by-products like wheat bran. The results clearly showed that additional wheat bran supplementation added to lablab hay increased milk yield of crossbred cows fed ML stover or OV hay basal diets thus confirming the hypothesis of this study. It was, therefore, recommended that for optimum milk yield, crossbred cows consuming ML stover basal forages should be supplemented with a combination of 0.5% BW lablab hay and 2.50 kg DM wheat bran, while a combination of 0.9% BW lablab hay and 2.50 kg DM wheat bran was recommended as supplement for cows consuming OV hay basal forages.
Acknowledgements The authors are grateful to the International Livestock Research Institute (ILRI) and the Livestock Services Project (World Bank) in the Ministry of Agriculture, Animal Industry and Fisheries, Uganda for funding this study. We are greatly indebted to the late Professor N.N. Ummuna for the close supervision he rendered to this research and this paper is dedicated to him. The technical assistance of the staff members of ILRI, both at the Debre Zeit
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Research Station and Addis Ababa who contributed to this study during data collection and analysis is gratefully acknowledged. The computing skills of the staff of the Biometrics Department at ILRI, especially Mamadou Diedhiou, Zerihun Tadesse, Amare Atale and Aklilu Bogale, are also highly appreciated.
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