Effect of feeding protein according to ARC and NRC recommendations on dry matter intake, digestibility and production performance in crossbred cows in late lactation

Animal Feed Science and Technology 73 (1998) 271±279

Effect of feeding protein according to ARC and NRC recommendations on dry matter intake, digestibility and production performance in crossbred cows in late lactation M. Venkatesh1,a, U. Krishnamoorthyb, Farooq Mohammeda,*, B.P. Hegdeb a

Department of Animal Nutrition, Veterinary College, University of Agricultural Sciences, Hebbal, Bangalore, 560 024, India b Department of Dairy Production, Dairy Science College, University of Agricultural Sciences, Hebbal, Bangalore, 560 024, India Received 8 August 1997; accepted 2 March 1998

Abstract The effect of feeding protein according to the ARC (1984) and NRC (1989) recommendations on dry matter intake, digestibility, N balance, milk yield and milk composition was studied in crossbred dairy cows in late lactation. The study included a feeding trial and a metabolism trial. The feeding trial was conducted using eight multiparous cows in late lactation in a switch over design. The cows were divided into two groups of four cows. Group I (Gp I) received an ARC protein diet and Group II (Gp II) an NRC protein diet. The duration of the trial was fourteen weeks, each period lasting for seven weeks. The diet consisted of mixed straw of finger millet and paddy (FM-P) and a compound feed mixture (CFM). The roughage dry matter intake for Gp I and Gp II was 3.87 and 3.69 kg dÿ1, respectively. The 4% FCM yield (kg dÿ1) for the corresponding two groups was 6.44 and 6.75. The fat, SNF and protein contents (%) for Gp I and Gp II were, respectively 4.69, 8.82, 3.93 and 4.95, 9.04, 4.28. The difference between the two groups in roughage DMI, body condition score, milk yield and milk composition was not significant (P>0.05). The DOMD of the two diets was similar. However, N balance (g dÿ1) in Gp II (39) was significantly (P<0.01) higher than in Gp I (4). The

* Corresponding author. 1 Present address: Animal Nutrition Innovation Centre, Hindustan Lever Ltd., No. 67-D, Bommasandra Industrial Area, Hosur Road, Bommasandra, Bangalore 562 158, Karnataka, India. 0377-8401/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved PII S 0 3 7 7 - 8 4 0 1 ( 9 8 ) 0 0 1 5 1 - 5

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results indicated that although N balance improved with feeding higher UDP level according to NRC, it had no beneficial effect on roughage DMI, milk yield, milk composition and body condition score. Therefore, it is concluded that in crossbred cows in late lactation, with low levels of production, feeding protein according to the ARC recommendations is adequate. # 1998 Elsevier Science B.V. Keywords: Undegraded dietary protein; ARC; NRC; Dairy cows

1. Introduction Although the Agriculture Research Council (ARC, 1984) and National Research Council (NRC, 1989) protein systems for dairy cattle are both based on the requirements of rumen microbes and the host animal, the undegraded dietary protein (UDP) recommended by the NRC (NRC-UDP) is approximately 30% higher than the UDP recommended by the ARC (ARC-UDP). Comparison of NRC and ARC protein feeding in mid and late lactation cows producing upto 30 kg of milk per day revealed that the ARC-UDP is adequate (Robinson and Kennelly, 1988; Robinson et al., 1991). The difference between ARC-UDP and NRC-UDP for milk production in the range of 5 to 10 kg is about 315 g per day. In view of the shortage of feeds and fodders in the developing countries, a considerable saving in protein feeding can be achieved, if the ARC recommendation can be adopted for low producers. However, Ramachandra and Sampath (1995) reported that in crossbred cows (400 kg body weight) in early lactation fed with rice (Oryza sativa) straw and para grass (Brachiaria mutica) as the roughage, the supply of UDP at levels higher than the NRC-UDP increased milk yield from 8.5 to 10.0 kg, in spite of providing adequate RDP according to the NRC (1989) recommendations. This has resulted in a dilemma as to whether ARC-UDP or NRCUDP should be adopted to crossbred cows fed on crop residues and medium quality compound feeds. The requirement for UDP at higher levels of milk production is a consequence of the inability of the cows to eat adequate dry matter to produce microbial protein in quantities sufficient to meet the tissue requirement. With low quality roughages and compound feeds, microbial protein flow to the duodenum may be limited by inadequate rumen fermentable dry matter intake and/or lower microbial efficiency in the rumen. Nevertheless, in late lactation cows and in cows with low production levels, since the requirement for metabolizable protein is reduced and the feed consumption is more relative to milk production, rumen microbial protein may be sufficient to meet the tissue requirement. Although crossbred cows in India reaching a peak milk yield of 30 kg per day is not unusual, the average milk yield is not more than 8 kg per day. Under such circumstance, if ARC-UDP can be adopted, the feeding cost can be minimized to that extent. Therefore, this study was undertaken to examine whether feeding higher levels of UDP as recommended by NRC has any advantage over feeding of UDP as recommended by the ARC in crossbred cows fed with straw as the sole source of roughage.

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2. Materials and methods 2.1. Animals and diet Eight multiparous crossbred cows (Holstein FriesianBos indicus, or JerseyBos indicus) in late-lactation, inseminated but too early for pregnancy confirmation, were divided into two groups of four each based on the comparable milk yield, body weight, number of lactations completed and days in lactation (Gp I 216, Gp II 217). The experimental animals, housed in individual stalls, were provided with similar managemental practices. The diet of the experimental cows included mixed straw of finger millet (Eleucine coracana) and paddy (Oryza sativa) (FM-P) offered ad libitum (6 kg dÿ1) and a compound feed mixture (CFM) as a supplement to provide adequate energy, protein and other nutrients as specified by the ARC (1984) in Group I (Gp I) and NRC (1989) in Group II (Gp II). The ingredient composition of CFM(ARC) and CFM(NRC) is presented in Table 1. FM-P and CFM were offered separately. The daily allowance of CFM was calculated based on the previous weeks FM-P intake, milk yield, milk fat and body weight. The CFM was fed in two equal portions at 06.00 and 13.00 h while milking. The cows were milked by hand and were allowed to have free access to water at 08.00 and 15.00 h. 2.1.1. Lactation trial (LT) The lactation trial lasted for 14 weeks in two periods in a switch over design. Each period lasted for seven weeks with an adjustment period of two weeks and an observation period of five weeks. Feed intake and milk yield were recorded daily. Samples of FM-P and CFM offered were collected weekly once for the determination of dry matter. Two or three weeks samples were pooled for chemical analyses. Milk samples were taken one

Table 1 Ingredient composition (g kgÿ1as is) of the diets Ingredient

Gp I

Gp II

CFM Tapioca pulp Molasses Maize Sunflower meal, s.e.a Cotton seed meal, s.e. Rice bran, s.e. Urea Common salt Mineral mixture FM-Pb straw

630 237 95 189 78 ± ± 13 6 12 370

700 231 105 21 ± 128 186 8 7 14 300

Vitamin A acetate (5000 I.U. kgÿ1), Zinc oxide (10 mg kgÿ1) and Sodium sulphate (3.8 g kgÿ1 in Gp I and 3.0 g kgÿ1 in Gp II), were added to the compound feed mixture. a Solvent extracted. b FM-P strawˆMixed straw of finger millet and paddy.

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day per week. The cows were weighed once in a week, after milking, before having access to water. The body weights were recorded on a Weighing Platform Scale (Avery). The cows were also scored for the body condition at the beginning and the end of each period, on a 5 point scale (Edmonson et al., 1989). 2.1.2. Metabolism trial (MT) One metabolic trial lasting for five days was conducted in period II, during which the daily intake of feed and fodder, milk yield and output of faeces and urine were recorded. Faeces and urine were collected manually as and when voided and stored separately until weighed and sampled. Samples of feed offered, feed refusals, faeces and urine were collected every day in the morning. One thousandth by weight of the daily faeces voided by each animal was used for dry matter (DM) determination. DM in the feeds and faeces was determined by drying at 708C to a constant weight. Dried samples of each day for five days of collection were pooled, ground through a 1 mm sieve and preserved for chemical analyses and in vitro rumen studies. For N determination, the faeces samples (1/ 1000 of daily voids) were preserved in 25% sulphuric acid for five days. Samples of urine (1/500 of the total output) from individual animals were collected everyday in the morning for five days in a 500 ml Kjeldahl flask containing 15 ml concentrated sulphuric acid and stored at room temperature for N determination. 2.2. Chemical analyses The samples of feed and faeces were analysed for proximate constituents (AOAC, 1984) except for crude fibre (CF) which was determined according to the Indian Standards Institution (ISI, 1975). Neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin and silica were determined according to Van Soest and Robertson (1985). The metabolizable energy (ME) was determined according to Menke and Steingass (1988). UDP was determined using protease enzyme (Krishnamoorthy et al., 1983). The samples of milk were pooled in proportion to the corresponding yield in the morning and evening. Total solids, protein and fat (Gerbers method) were determined according to AOAC (1984). 2.3. Statistical analysis The data of the feeding trial were analysed by an analysis of variance (ANOVA) in a switch over design with two periods and two treatments (Federer, 1967). The data of the metabolism trial were analysed by the Student `t'test (Snedecor and Cochran, 1968). 3. Results 3.1. Lactation trial The chemical composition of FM-P and CFM (for the three composite samples collected during the experimental period) is presented in Table 2.

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Table 2 Chemical composition (g kgÿ1DM) of compound feed mixture (CFM) and mixed straw (FM-P) used in the lactation trial (LT) and metabolism trial (MT) CFM Gp I Crude protein Ether extract Crude fibre Total ash Neutral detergent fibre Acid detergent fibre Acid detergent lignin ME (MJ kgÿ1 DM) UDP a Protease insoluble CP a

126 14 133 110 382 147 84 10.3 15 21

FM-P Gp II 155 10 169 145 400 221 125 8.4 59 48

LT

MT

36 11 400 58 824 524 64 5.2 21 22

63 16 365 159 804 511 162 4.8 37 36

Undegraded dietary protein, calculated from the published data (Sampath, 1990).

3.1.1. Feed intake, body weight and condition score, milk yield and milk composition The mean daily intakes of DM, NDF and ADF, average body weight, condition score, milk yield and milk composition for the two groups over 5 weeks are presented in Table 3. The intake of DM, NDF and ADF in Gp II was significantly higher than in Gp I. The change in condition score for Gp I and Gp II was ÿ0.13 and ÿ0.11, respectively and was not significantly (P>0.05) different. The mean daily 4% FCM yield (kg) for Gp I and Gp II was 6.44 and 6.75, respectively. The difference between the two groups for milk yield, 4% FCM and milk composition (total solids, fat, solids not fat, protein) was not significant (P>0.05). 3.2. Metabolism trial The mean intake and digestibility of DM, OM and N balance for the two groups are presented in Table 4. The digestibility of DM, OM and fibre fractions in the two groups was similar. The difference between the two groups in DOMD was not statistically significant. The daily intake and faecal excretion of N (g) for Gp II (234, 107) were significantly higher than for Gp I (174, 82). However, the urinary N excretion for Gp I and Gp II were 55 and 48, respectively and the difference was not significant. N retention (g dÿ1) in Gp I and II was, respectively, 4 and 39 and the difference was statistically significant (P<.01).

4. Discussion The CFM of Gp I and Gp II differed in chemical composition, ME content and RDP : UDP ratio. The protease insoluble protein (PIP) of CFM for Gp I and FM-P agreed closely with the UDP content calculated from the published dacron bag data (Sampath, 1990). Although the PIP of the CFM for Gp II was lower (48 g/kg) than the calculated

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Table 3 Body weight (kg), body condition score, intake (kg dÿ1) of DM, CP, NDF and ADF, milk yield (kg dÿ1) and milk composition (%) for the two groups during the lactation trial (MeanSE)

Body weight Body condition score Initial Final Gain Intake Dry matter Roughage CFM Total Crude protein RDP UDP NDF ADF Milk yield and composition Yield Total 4% FCM Composition Total solids Fat SNF Protein

Gp I

Gp II

367

370

3.38 3.25 ÿ0.13

3.43 3.32 ÿ0.11

NS

3.870.34 6.550.25 10.420.25 0.970.02 0.740.02 0.230.01 5.680.23 2.990.15

3.690.16 8.800.20 12.490.20 1.490.03 0.980.02 0.510.01 6.550.12 3.840.08

NS ** ** ** * ** ** **

5.860.25 6.440.81

5.930.25 6.750.21

NS NS

13.510.22 4.690.12 8.820.13 3.930.10

13.990.25 4.950.17 9.040.10 4.280.15

NS NS NS NS

NSˆNot significant (P>0.05).

UDP (59 g/kg), the difference between the two diets in UDP content was sufficiently large as desired. Although the total DMI for Gp II was significantly higher than for Gp I, the intake of roughage DM by the two groups was similar. Therefore, the higher intake of DM, NDF and ADF in Gp II is attributable to the higher allowance of CFM (Table 3). The different allowance of CFM for the two groups was necessary, to meet the protein requirements according to ARC in Gp I and NRC in Gp II, while assuring a similar supply of energy. The formulation of CFM (ARC) with a similar ME content as in CFM (NRC) but much lower UDP content was difficult because of the limited choice of available ingredients. To avoid possibilities of rumen degradable protein sources (urea vs feed proteins) and fermentation rate of feedstuffs, influencing microbial protein flow to the duodenum, the two CFM were formulated to be similar in source of rumen degraded proteins and fermentation rate to the extent possible. The use of urea as the sole source of RDP in CFM (ARC) was not favoured since this would necessitate the use of the same source of RDP in CFM (NRC). But to have urea as the sole source of RDP in CFM (NRC) was not possible because the feedstuffs chosen for UDP also contributed substantial amount of RDP. Since the RDP of feed origin, unlike urea, contributed proteins and amino acids,

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Table 4 Body weight (kg), DMI (kg dÿ1), digestibility (%) and N balance (g dÿ1) for the two groups during the metabolism trial

Body weight Intake Roughage CFM Total Digestibility Dry matter Organic matter Crude protein Crude fibre Ether extract Neutral detergent fibre Acid detergent fibre TDN DOMD Nitrogen balance N intake N output Milk Faeces Urine N retained

Gp I

Gp II

367

371

5.000.09 6.100.20 11.100.16

3.710.37 7.890.37 11.600.39

* ** NS

48.02.53 53.52.22 52.72.55 34.94.83 47.11.70 40.03.57 17.24.58 47.11.63 46.51.92

51.61.92 57.51.73 54.32.00 38.61.74 36.43.17 40.03.00 25.02.62 49.41.31 48.91.48

NS NS NS NS * NS NS NS NS

1743.64

2348.20

**

333.50 826.08 555.15 42.85

401.43 1074.10 484.05 3911.20

NS ** NS **

CFM (ARC) was formulated to provide 50% RDP of feed origin while limiting the level of UDP. Apart from this, it was also intended to have similar fermentation characteristics for the energy components. The fermentation rate (k) for CFM of Gp I and Gp II, calculated from the published data on fermentation kinetics for different ingredients (Krishnamoorthy et al., 1995 and unpublished data) were 0.112 hÿ1 and 0.108 hÿ1, respectively. Therefore, although the ARC (1984) recommends 130 g UDP for cows producing 5 kg of milk, supply of UDP marginally in excess of the recommendation could not be avoided. The RDP and UDP supplied (kg) in Gp I were 0.74 and 0.23, compared with the ARC (1984) recommendation of 0.69 and 0.13, respectively. The respective figures for Gp II were 0.98 and 0.51, compared with the NRC recommendation of 0.70 and 0.48. The higher amount of UDP fed to Gp II neither influenced body condition score, nor milk yield and milk composition (Table 3) suggesting that protein feeding according to ARC is adequate to support low levels of milk production. Robinson and Kennelly (1988) and Robinson et al. (1991) reported that for cows in mid and late lactation producing upto 30 kg of milk, fed on silage diets, UDP levels recommended by ARC are adequate. In view of these findings, increase in milk yield on feeding more UDP than the NRC levels (Baradkar et al., 1995; Sampath et al., 1995; Walli et al., 1995; Kalbande and Thomas, 1995) should be considered with caution. The response in milk production to UDP supply may vary with the energy status of the cows (érskov et al., 1981). The digestibility of the two diets was similar, resulting in ME

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contents of 7.12 and 7.47 MJ/kg DM, respectively (Table 4). The mean ME intake, calculated from the mean DMI in the feeding trial (10.42 and 12.49 kg) and the ME content of the diet obtained from the digestion trial and corrected to level of intake (7.50 and 7.94 MJ) (NRC, 1989; Nataraja et al., 1998), for the entire feeding trial for Gp I and Gp II was 78.2 and 99.2 MJ/day, respectively. Since the average body weight and 4% FCM yield for the two groups were 367, 6.4 and 370, 6.8, respectively, ME requirement (MJ) for maintenance and milk yield for Gp I and Gp II are respectively 76.0 and 78.5 (ARC, 1980) and 81.4 and 83.7 (NRC, 1989). Thus, ME supplied in the diet for both groups was adequate to support maintenance and milk production. Although the body condition score reflected otherwise (Table 3) and the body weights revealed neither gain nor loss, the positive N balance in both groups supports this view. A significantly higher N retention in Gp II (Table 4) may be considered as the effect of feeding higher amounts of both RDP and UDP under positive energy balance. Although the supply of additional RDP and UDP in Gp II increased N retention, it had no effect on roughage DMI, milk yield and milk composition indicating that feeding protein according to ARC (1984) recommendation may be adequate.

5. Conclusions Feeding of protein according to NRC (1989) recommendations improved N balance but had no influence on roughage DMI, milk yield and milk composition as compared to feeding protein according to ARC (1984). Therefore, protein feeding according to ARC may be adequate to support the low levels of milk production (7 kg d) in crossbred cows fed on low quality roughages. Since the difference between the ARC and NRC protein feeding recommendation at this level of production is about 315 g, adoption of the ARC (1984) recommendation would be advantageous in view of the need to use scarce and rather expensive feeds in an economic way. Acknowledgements The authors wish to thank M/s Mysore Feeds Bangalore, India, for providing the supplements. This work was a part of the project `Studies on nitrogen utilization in ruminants' (DR/UAS/9 and 11/96) jointly sponsored by the Alexander von Humboldt Foundation, Germany in the form of equipment donation and the University of Agricultural Sciences, Hebbal, Bangalore, India.

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