The effect of protein supplement source or supply pattern on the intake, digestibility, rumen kinetics, nitrogen utilisation and growth of Ethiopian Menz sheep fed teff straw

ANIMAL FEED SCIENCE AND TECHNOLOCY

ELSFYIER

Animal Feed Science Technology 64 ( 19%) 1I-25

The effect of protein supplement source or supply pattern on the intake, digestibility, rumen kinetics, nitrogen utilisation and growth of Ethiopian Menz sheep fed teff straw M.L.K. Bonsi a’*, AX. Tuah a, P.O. Osuji b, V.I. Nsahlai b, N.N. Umunna b a Department of Animal Science, University of Science and Technology (UST), Kumasi, Ghana b International Livestock Research Institute, Addis Ababa. Ethiopia

Accepted9 May 1996

Abstract A series of trials were conducted to study the effect of either nitrogen source or supply pattern on the growth, rumen fermentation pattern and utilisation of straw by Ethiopian Menz sheep. All experimental sheep were given teff straw basal diet (CON). Irrespective of the trial, treatment sheep were offered either cottonseed cake (CSC), leucaena (LEU) and sesbania (SESM) in the morning prior to teff straw. Additional treatments with sesbania were offered either in the evening (SESE) or morning and evening (SESME). Measurements included roughage intake, digestibility, kinetics, rumen fermentation patterns, nitrogen utilisation, microbial protein supply and growth of sheep. Rate of degradation was highest (P < 0.05) when sesbania was offered once a day compared with twice a day, while supplementation produced higher (P < 0.05) liquid passage rates. Diets with sesbania produced higher (P < 0.05) roughage intake compared with leucaena. Microbial protein supply as well as N economy were similar (P > 0.05) among the foliage diets irrespective of source, time or frequency of feeding. Supplementation enhanced (P < 0.001) growth rates in sheep, while cottonseed cake (CSC) diet was superior (P < 0.01) to the fodder trees. Growth rates declined across treatments during the second phase (6-10 weeks) compared with the initial period

* Corresponding author. 0377~8401/96/$15.00 Copyright 0 1996 Elsevier Science B.V. All rights reserved. HI SO377-8401(96)01048-6

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M.L.K. Bonsi et al. /Animal Feed Science Technology 64 (19%) I I-25

(l-6 weeks). It is also possible for farmers to feed sesbania evening or twice daily without any detrimental effects.

supplements

in the morning

or

Keywords: Digestibility; Growth; Intake; Supplement source; Supply pattern

1. Introduction Differences in the rate and extent of digestion of foliages require varied supplementation strategies to optimise the performance of animals fed poor quality forages (Bonsi et al., 1994; Bonsi et al., 1995). In previous studies with sheep fed isonitrogenous supplements (leucaena and sesbania) (Bonsi et al., 19951, it was deduced that fast degradation of sesbania resulted in increased concentration of rumen metabolites (ammonia nitrogen, minerals, isoacids) compared with leucaena. These occurrences resulted in a proportionately higher intake, digestibility and nitrogen utilisation with sesbania diets compared with leucaena diets (Bonsi et al., 1994). It was therefore hypothesised that these attributes of sesbania might result in higher growth rates in sheep compared with when fed leucaena. Teff straw, like many tropical forages, is very fibrous and degrades slowly (700 g kg-’ > (Osuji, 1994) compared with leaves from trees (Bonsi et al., 1995). When diets containing concentrates are fed more frequently, improved animal performance occurs through an even rumen fermentation pattern (Gibson, 1981). Bacterial growth rate and microbial protein synthesis are some beneficial effects observed in synchronising the release of protein and energy (Henning et al., 1991; Sinclair et al., 1993) although there have been some contrary findings (Herrera-Saldana et al., 1990; Khalili and Huhtanen, 1991). Sesbania has been found (Ahn et al., 1989; Bonsi et al., 1994) to degrade faster than foliages like leucaena or gliricidia. A second or an evening supplementation with sesbania may ensure sustainable release of critical nutrients which might improve nitrogen utilisation by coupling energy release from the slow fermenting roughage. Beneficial effects of more frequent feeding were possible in the event of protein and energy restriction or inadequacy (Robinson and McQueen, 1993). Since these two nutrients are inadequate where low quality roughages form the basal diet, the pattern of supplementation may be beneficial in foliage-containing diets. Unlike protein and energy concentrates, the use of fodder trees to investigate the beneficial effects of supply patterns has yet to be explored. Feeding sesbania in the evening or twice a day could enhance roughage utilisation, promote high microbial protein synthesis and growth of sheep through the coupling of the release of energy and protein from the low quality roughage (teff straw) and sesbania. Cottonseed cake served as a positive control in this study. The objectives of this study were: 1. to determine the effect of supplementing teff straw with cottonseed cake, dry leucaena or sesbania on the intake, digestibility, nitrogen balance, rumen kinetics, ammonia-nitrogen, microbial protein synthesis and growth of sheep; 2. to optimise animal response using the above parameters as indices by supplying sesbania at different times or frequencies.

M.L.K. Bonsi et al./Animal Feed Science Technology 64 (1996) 11-25

13

2. Materials and methods 2.1. Diets The diets offered for sheep on the various treatments during the growth, metabolism and kinetics studies were similar. Unchopped teff straw (Eragrostis tef) was given either alone (CON) or supplemented with cottonseed cake (CSC), sundried leaves of Leucuena leucocephalu (LEU) or sundried leaves of Sesbania se&an fed either in the morning (SESM), evening (SESE) or morning and evening (SESME). The amount of supplement offered was based on 19.56 g kg - ’ BW0.75 (Osuji et al., 1993) and 22 g kg-’ W”.75 (Bonsi et al., 1994) for CSC and the foliages, respectively, estimated to optimise roughage intake in our laboratory. Teff straw was fed ad libitum (about 1000 g h- ’ to ensure about 20% refusal) after complete consumption of the morning supplements, but was fed at 08:OOh to sheep on SESE treatment. Sheep on SESE and SESME treatments had their sesbania supplements offered in separate containers. No minerals were supplied to all the sheep. 2.2. Kinetic studies Twenty-four rumen fistulated Ethiopian Menz sheep (mean f SD body weight 21.9 + 2.42 kg, range 15.8-24.6 kg) about 12 months old, were blocked by weight into six groups. The sheep in each group were randomly assigned to the six dietary treatments in a completely randomised block design. A 1Cday adaptation period was allowed prior to 12 days of data collection. Animals were housed in individual pens with slatted floors equipped with metal feeding and water troughs. All experimental sheep were dewormed regularly. The degradability of teff straw was estimated using the procedure described earlier by Bonsi et al. (1995). Teff straw was ground (2 mm> and samples (2.5 g) put into nylon bags (6 cm X 12 cm and 41 pm pore size; Polymon, Switzerland). Teff straw was incubated in quadruplicate for 3,6, 12,24,48,72,96 and 120 h. On removal of the bags at the end of each incubation time, the bags were rinsed under tap water and stored in a freezer. At the end of each period, samples were washed in a washing machine (Tefal Altematic, Finland) for five cycles of 6 min each and dried in an oven at 60°C for 48 h. A set of bags not incubated (0 h), but containing each of the feed samples was washed and dried under similar conditions. To determine particulate passage rates, teff straw was mordanted with chromium (Uden et al., 1980). Sheep were dosed through the fistula with about 15 g of unchopped mordanted straw at 08:OOh. Faecal samples were collected every 8 h for 72 h, and every 12 h for the next 72 h during the 6-day faecal collection period. The faeces were dried at 100°C for 24 h, ground (1 mm) and stored pending chromium determination. For liquid passage rate measurement, 50 ml of Co-EDTA solution (5.39 mg Co 1-l ) were injected, with a syringe, through the cannula into the mmen at OS:00 h, just before the supplement allocation was given. Rumen fluid was collected at 1, 2, 3, 6, 9, 12, 18 and 24 h after dosing. The rumen fluid was centrifuged and the supematant stored for cobalt analysis.

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M.L.K. Bonsi et al./Animal Feed Science Technology 64 (1996) 11-25

2.3. Growth trial

Thirty Ethiopian Menz sheep (mean + SD body weight 18.31 f 1SO kg, range 15.8-21 kg) about 12 months old, were blocked by weight into six groups in a completely randomised block design (CRBD). The experiment lasted for 84 days (comprising 14 days of adaptation, and 70 days of intake and growth study). Housing and management were similar to the kinetic study. 2.4. Metabolism study After the intake and growth study (12 weeks), four sheep from each treatment were selected (Blocks l-4) and transferred to metabolism crates. After 5 days of adaptation to metabolism crates and harnesses, total faeces and urine were collected for 6 days. 2.4.1. Measurements Faecal bags were used to collect faeces. Faeces were removed every morning, weighed, sampled (100 g kg-‘) and pooled on animal basis. The pooled samples were dried at 60°C for 48 h, ground (1 mm mesh) and stored in plastic containers at room temperature pending analysis. Urine was collected over 25 ml (10%) hydrochloric acid. A sample (50 ml 1-l > of urine was taken each day, pooled for each animal and stored frozen pending nitrogen analysis. The remaining urine was diluted to 2 1 with water and samples taken for analyses of purine derivatives. At the end of the collection, rumen fluid was sampled at 1, 2, 4, 9, 12, 18 and 24 h after morning feeding using a pump and stomach tube. The 10-h rumen fluid was sampled exclusively for sheep given sesbania in the evening or twice daily. The rumen fluid was stirred with a magnetic stirrer (Stuart Scientific, SM8) and the pH read (Kent EIL 7045/46). About 0.15 ml of concentrated hydrochloric acid were added to the rumen fluid samples in plastic containers and stored at - 4°C pending ammonia nitrogen determination. 2.5. Chemical analyses

Dry matter (DM) and organic matter (OM) were determined according to the Association of Official Analytical Chemists (1975). Neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) were determined following the method of Van Soest et al. (1991). Nitrogen (N) and ammonia-N in the rumen fluid were determined by distillation using the micro-Kjeldahl procedure (Tecator 1026, Tecator, Hoganas, Sweden). Faecal samples for the determination of particulate passage were digested at 150°C for 2 h (using 1016 Tecator Digester) by the addition of 3 ml sulphuric, 2 ml perchloric and 1.5 ml nitric acids sequentially to the feed samples in the tubes. The rumen fluid sampled for cobalt analysis was centrifuged at 2016 X g for 10 min and the supematant stored. Chromium (deionised water added to the solution in the microtube up to the 75 ml mark the tubes were then covered with cellophane and shaken to a uniform concentration) and cobalt concentrations were assayed with an atomic absorption spectrophotometer (Perkin-Elmer 2380, USA). The flow rate, combus tion temperature and lamp type were set according to the manufacturer’s instructions.

M.L.K. Bonsi et al./Anitnal Feed Science Technology 64 (1996) II-25

15

The sample was injected with a microlitre syringe and the sample atomised to read the concentration. 2.6. Data and statistical analyses Growth rate was determined using simple regression analysis. The disappearance of dry matter from nylon bags was described by an exponential model (P = a + b(1 - e-“‘1 Orskov and McDonald, 1979) where P is DM disappearance at time t, a is the zero time intercept, b is the slowly degradable fraction and c is the rate of degradation. The lag time (TL) was calculated as follows TL = {(- l/c>ln[ 1 - ((w - a)/b)])where w is the washing loss. The fractional rates of particulate passage were derived by fitting the model of Grovum and Williams (1973) to the passage data: Y = 0 for t < ZT and y=Ae-kl(f-TT)_Aek2('TT) for t 2 l’T where Y and A are chromium concentrations in the faecal DM at time t after dosage,’ k, and k, are the rate constants, n is the calculated time for first appearance of the marker in the faeces. First, the initial values for the rate constants (k, and k2) and the transit time (P) were estimated. Then, by using a curve-fitting package which allows direct iterative estimation of non-linear parameters, the final values of the rate constants and transit time were determined from the computer. Graphically, the natural logarithm of the marker concentration in the faeces DM was plotted against time and regression analysis performed as the linear portion of the descending slope. The regression coefficient and the Y-intercept correspond to the slowest rate constant (K,) and A,, respectively. The liquid outflow rate was estimated using the non-linear model: C = Aemklx’, where C is Co concentration with time, A is the predicted zero time concentration and k, is the fractional liquid outflow rate. The rumen liquid volume (Ru) was calculated as dose/A and the absolute outflow rate as Rv X k,. The differences between treatments with respect to rumen ammonia concentration and pH were analysed using repeated measure analyses (Wirier, 1971; Statistical Analysis Systems Institute Inc., 1987). All variables were subjected to analysis of variance (ANOVA) using the general linear models (GLM) (Statistical Analysis Systems Institute Inc., 1987). The other supplements were isolated before analysing for the effect of supply pattern of sesbania. The treatment sums of square were further partitioned into linear components of the non-orthogonal contrasts: (1) 1 vs. rest; (2) 2 vs. 3 and 4; (3) 3 vs. 4; (4) 4 vs. 5; (5) 4 and 5 vs. 6.

3. Results 3.1. Kinetic study. The chemical composition of the experimental diets is shown in Table 1. Teff straw was incubated in the rumens of sheep fed the various diets for 120 h. The intercept or rapidly soluble fraction (a), potentially degradable fraction (6) and the potential degradability (PD = a + b) were similar (P > 0.05) for all treatments (Table 2). Sesbania offered in the morning increased (P < 0.05) the rate of degradation (c) of teff straw

M.LK. Bonsi et al./Animal

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Feed Science Technology 64 (1996) II-25

Table 1 Chemical composition of experimental feeds Parameter a Drymattercgkg-‘)

gkg-'

cake

Leucaena leucocephala

Sesbania sesban

951

940

930

934

911

914 454 210 244 77.8 28.5

901 280 158 122 39.6 10.4 185.3 28.96

889 272 193 79 38.4 8.7 151.5 13.21

Teff straw

Cottonseed

DM

Organic matter NDF ADF Hemicellulose Nitrogen NDF-N Soluble tannins Condensed tannins (550 nm g - ’ NDF)

804 478 326 7.0 4.4 54.2 3.24

11.86

a NDF, neutral detergent tibre; ADF, acid detergent fibre; NDF-N, NDF nitrogen.

Table 2 Rumen degradation and rate of passage characteristics of teff straw observed in Ethiopian Menz sheep fed teff straw only (CON) supplemented with cottonseed cake (CSC), leucaena (LEU) or sesbania offered in the morning (SESM), evening (SESE) or morning and evening (SESME) Parameter a

CON

csc

LEU

SESM

SESE

SESME

133 199 234 332 427 557 604 651

150 147 228 348 494 563 593 660

150 139 206 320 338 461 501 553

123 152 163 221 328 382 526 489

110 659

SED (n=4)

F-value

Dry matter disappearance (g kg - ‘) Incubation time (h)

0 3 6 12 24 48 72 % 120

106 115 122 122 328 409 399 432 581

126 141 211 285 408 520 568 549

Degradation constants (g kg - ‘) a 87 81 b 487 593 PD(a+b) 574 674 c (h-‘1 0.0167 0.0228 Rate of passage k,, (h-‘1

Rumen volume (1) Flow rate (I h- ’) k,, (h-l) RTR (h)

124

93

73

623

592

471

26.2 100.3 747 688 545 769 111.1 0.0165 0.0227 0.0363 0.0101 0.01107

0.075

0.091

0.089

0.102

8.07

7.69 0.707 0.014 -73

9.15 0.808 0.020 55

8.22 0.83 1 0.024 56

0.609 0.019 54

17.9 16.5 33.3 62.7 56.6 53.9 53.9 37.9

0.109 8.79 0.948 0.014 77

0.0% 9.93 0.836 0.018 59

0.0122 1.001 0.0%75 0.0058 14.4

NS ** NS NS NS ** * **

NS NS NS NS

NS NS NS NS NS

a a, intercept; b, potentially degradable component; c, rate of degradation; PD, potential degradability; k,,, the fractional outflow rate. of liquid from the rumen; klpr fractional outflow rate of particulate matter from the rumen; RTR, retention time in the rumen. SED, standard error of difference. NS, P > 0.05; P < 0.01; * P < 0.05. ?? ??

M.L.K. Bonsi et al./Animol

Feed Science Technology 64 (19%) II-25

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compared with twice daily feeding. Supplementation increased potential degradability (P < 0.05). Sesbania offered in the morning only tended to increase (P < 0.06) the rate of degradation (Table 2) compared with evening (5) or morning and evening (6) supplies. Supplementation improved (P < 0.05) the fractional outflow rate and flow rate of liquid (Table 21, but no differences (P > 0.05) were observed between the foliage types. Dietary treatment had no effect on particulate passage rate (k,,) or retention time in the rumen (RTR). The time or frequency of sesbania offer did not influence (P > 0.05) the kinetics of roughage in the rumen. 3.2. Growth study Supplementation tended to enhance (P < 0.09) straw intake (Table 3). Intake of teff straw and total DM tended to increase (P < 0.06) for sesbania compared with leucaena. Compared with the teff straw only diet (negative control), total intakes of DM, OM, NDF, ADF, hemicellulose, nitrogen and NDF-N were increased (P < 0.001) by supple-

Table 3 Feed intakes and growth rates of Ethiopian Menz sheep fed teff straw only (CON) supplemented with either cottonseed cake (CSC), Leucaeno (LEU) or Sesbania offered in the morning (SESM), evening (SESE) or morning and evening (SESME) Parameter

*

Intake Teff straw (g DM) Teff straw (g DM kg-’ W”.75) Supplements (g DM) Total feed (g DM) Total feed (g DM kg- ’W”.75) Organic matter(g) NDF (g) ADF (g) Hemicellulose (g) Nitrogen (g) NDF-N (g) Growth Initial weight (kg) Final weight (kg) Growth rate (g day- ’) 1-42 days 43-70 days 70 days Growth (g g - ’ N intake) FCE b (gain/feed)

CON

csc

LEU

SESM

SESE

SESME

SED (n=S)

P-value

508 58.6 0 508 58.6 463 408 243 165 3.6 2.2

564 60.1 169 733 78.1 668 530 305 225 17.1 7.3

544 60.6 193 737 81.9 670 492 291 201 11.4 4.4

543 59.3 192 735 80.4 666 489 297 192 11.2 4.1

548 58.3 192 740 78.9 670 493 299 194 11.2 4.1

568 61.3 193 761 82.2 689 509 309 200 11.4 4.2

30.5 3.02 30.5 3.01 27.8 24.5 14.6 9.9 0.21 0.13

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

17.84 16.88

17.86 23.26

17.84 21.20

17.84 21.26

17.75 21.33

17.86 21.26

- 15.9 -22.8 - 19.9 -5.69 -0.039

85.7 51.0 62.9 3.72 0.086

49.1 30.9 37.8 3.29 0.051

60.5 26.5 42.4 3.66 0.058

61.2 16.6 32.6 2.89 0.044

59.7 19.5 35.8 3.17 0.047

a See Tables 1 and 2 for explanation b Feed conversion efficiency.

of abbreviations.

1.037 1.026 10.16 8.01 7.19 -

NS NS *** *** *** -

rnen~~on~ There

were no differences tP > 0.051 for these variables amcxlg the supplements or between the times and &quency of sesbania supp!y_ Sheep given the negative control diet experienced weight loss and differed (P < 0.001) from supplemented sheep (Table 3). The positive control (CSCS diet promoted higher (P < 0.001) growth rates than the foliage-containing diets. Similar CP > 0.05) growth rates were observed in sheep fed leucaena or sesbania diets. Growth was higher for all supplemented sheep within the initial 6 weeks compared with the last 4 weeks. Sesbania supplied in the morning, evening or twice daily effected similar (P > 0X15)growth responses.

The nutrient intakes and d~~stib~~~~es dming the ~~~~j~ trial are indicated in Table 4. Supplementation increased (P < 0.1) straw intake. Suppleme~t~tjon improved the intakes of total DM cP < Oldie, GM, NDF, ADF and herni~l~~lose f P < 0.01). R&age supplements enhaneed (P < 0.0505) total DM intake in sheep compared with cottonseed cake. Leucaena, compared with sesbanja, depressed (P < 0.01) ADF dig~stib~li~.Neither time nor frequency of feeding sesbania ~~uenced nutrient digestibility, Nitrogen and ND&N intakes were lower (P < 0_001) for sheep fed the unsupplemented &et while sheep given the CSC diet had higher fP < 0.001) intakes of N and

Table 4 Fe& intakes and d~g~~ti~i~~d~durbg the rne~~~~rn study wittr Ed&p&m Menu sheep fed reff stmw on& fCON1 s~~pierne~~d with either cait~nseed cake (CSC), Ieucaena @EU> or sesbania offered in the morning fSESM), evening 6~s~)ormorning and eve13ing 6Esb2~) Parameter a

CON

CSC

LEU

SESM

SJZSE

SESME

SED (n=4)

P-value

hake Teff straw (g DM) Teff straw tg DM kg- ’) Tatal feed (g DM) Total feed (g DM kg- ’) ?&g&c matter t9) NDF tg> ADF &I ~ern~i~M~~ (9, DOMI b

500 50.58 5oa 50.5g 456 4&?. 239 163 194

538 54.42 707 71.7.5 645 510 293 217 393

548 55.26 740 74.72 672 494 292 202 372

601 60.5g 794 go.02 719 536 325 2lf 403

557 56.35 749 75.88 679 500 303 $97 365

56 56.41 752 75.79 681 503 305 198 395

27.1 2,826 27.1 2.W 24.7 21.8 12.9 8s 18.9

NS NS *** *** *** + ** * ***

~~~~~~b~~~~~~~~~ ? Dry matter ~~~i~ matter NDF ADF ~~rn~~~~~~~~

490 518 544 so3 604

539 568 579 511 672

521 546 516 360 741

524 5.53 544 478 644

510 537 525 434 667

545 574 558 474 688

26.7 26.8 30.4 34.4 36.1

NS NS NS ** *

’ See Tables I and 2. b ~~g~~~~~ organic ma8er Ins&e_

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19

Table 5 Rumen characteristics, nitrogen utilisation and microbial protein synthesis in Ethiopian Menz sheep fed teff straw only (CON) supplemented with cottonseed cake (CSC), leucaena (LEUC) or sesbania offered in the morning (SESM), evening (SESE) or morning and evening (SESME) CON

Parameter a

csc

LEU

SESM

SESE

SESME

SED

P-value

(n=4) Rumen characteristics

PU Minimum Maximum Mean Ammonia (mg N I- ’) Minimum Maximum Mean

6.0 7.0 6.69 20 33 26

6.0 6.9 6.45

6.0 7.0 6.54

6.2 7.0 6.61

158 263 210

138 85

3.5 15 2.20 2.18 0.33 243 577 0.37 125

16.93 44 7.19 6.11 5.14 647 718 6.05 350

11.46 11.59 31 29 4.41 4.32 6.65 5.14 1.39 2.05 424 560 256 491 3.49 4.49 303 384

1.98 0.67 2.65 3.15 2.29 12.2

8.01

16.26

48

82 203 136

6.1 7.0 6.75 64 206 132

5.9 7.1 6.65 87 160 119

0.065

_ **

9.8

_ ***

0.189 1.6 0.119 0.246 0.199 24.6 63.9 0.225 30.9

*** *** *** *** *** *** *** *** ***

Nitrogen urilisation

Nintake(gday”) N intake (g kg-’ DOMI) NDFN intake (g day-’ ) Faecal N (g day-’) Urinary N (g day“) N digestibility (g kg-‘) NDFN digestibility (g kg- ’) N balance (g day-‘) N balance (g kg-’ N intake)

11.28 11.31 31 29 4.12 4.14 5.02 4.64 2.16 2.27 556 592 503 512 4.11 4.46 365 392

Microbial protein

Allantoin (mmol day .’) Uric acid (mmol day-‘) Total PDs b (mmol day-‘) Microbial PDs (mmol day- ’) Microbial N (g day“) Microbial efficiency (g kg- ’ DOMU ’ Microbial efftciency (g kg - ’OMADR) d

9.35 11.13 8.09 20.80

6.11 1.24 7.35 8.75 6.36 15.98

6.21 1.30 7.51 8.94 6.50 17.46

7.49 1.15 8.64 10.28 7.47 20.57

6.10 1.26 7.35 8.75 6.36 16.20

0.889 0.127 0.889 1.058 0.769 2.668

*** *** *** *** *** *

27.74

21.31

23.27

27.43

21.59

3.557

*

1.34

a See Tables 1 and 2. b Total PDs (purine derivatives) was the sum of allantoin + uric acid. ’ Digestible organic matter intake. d OM apparently digested in the rumen (OMADR) = 0.75 (Osuji et al., 1993). SED, standard error of difference. NS, P > 0.05; * P < 0.05; * P < 0.01; * * * P < 0.001. ??

NDF-N compared with the foliage-containing diets (Table 5). Nitrogen and NDF-N digestibilities varied (P < O.OOl>among the treatments. Sheep given the sesbania diets had similar (P > 0.05) digestibilities of nitrogen and NDF-N. Sheep offered the negative control diet had lower (P < O.OOl> faecal and urinary nitrogen outputs than the supplemented ones. Urinary nitrogen output was higher (P < 0.001) for the CSC fed sheep than for the foliage fed ones. Between the two foliages, leucaena feeding

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Feed Science Technology 64 (1996) II-25

produced lower (P < 0.01) urinary nitrogen than sesbania, irrespective of the supply pattern, while the reverse trend was observed for faecal nitrogen. The sesbania-fed sheep produced similar (P > 0.05) urinary nitrogen output, but twice daily feeding tended to reduce (P < 0.08) faecal nitrogen output. Nitrogen balance (g day-’ ) was lowest (P < 0.001) in the control diet. The CSC diet promoted higher (P < 0.001) nitrogen balance than the foliages, while leucaena relative to sesbania, depressed (P < 0.05) nitrogen balance. Time or frequency of feeding sesbania did not affect (P > 0.05) nitrogen balance. Supplementation elicited greater (P < 0.001) urinary concentrations of allantoin, uric acid, total purine derivatives (PD), microbial-N and efficiency of microbial-N synthesis (Table 5). The CSC diet produced higher (P < 0.05) levels of allantoin, microbial PD and nitrogen than ‘the two foliages, which were similar (P > 0.05). Though the frequency of sesbania feeding did not influence (P > 0.05) the excretion of purine derivatives, sesbania offered in the evening tended to enhance (P < 0.1) microbial N efficiency (g kg- ’ OMADR) compared with morning feeding. 3.4. Rumen characteristics All mean pH values were above 6.4 (Table 5). The negative control diet had higher (P < 0.01) pH value than the CSC or leucaena-containing diets. Time X treatment interaction was significant for rumen pH (P < 0.001) but not significant (P > 0.05) for NH,-N. Sheep given the CSC diet elicited higher (P < 0.001) ammonia levels than the foliage-containing diets, which differed (P < 0.01) in favour of sesbania. Feeding sesbania in the morning tended to stimulate (P < 0.08) higher ammonia concentration compared with morning and evening feeding, but not evening alone (P > 0.05).

4. Discussion 4.1. Protein source In this study, roughage intake and nutrient digestibility were proportionately improved by 0.13 and 0.06, respectively, in the foliage- supplemented diets. The stimulatory effect of the foliage supplements on nutrient intake and digestibility of cell wall was expected since sesbania and leucaena have higher nutrient concentrations (Bonsi et al., 1995) and degrade faster than teff straw (Bonsi et al., 1995). The rapid degradation of the foliages, especially sesbania (Bonsi et al., 1995) was reflected in the high rumen ammonia-nitrogen release which is an index of rumen proteolytic activity (Woodward and Reed, 1989). The higher roughage intake experienced with the supplemented diets, especially in sesbania-fed sheep, could be a sum of various activities. The leucaena, which is less digestible than sesbania, provides less energy to the rumen microbes to effect particle breakdown. Moreover, leucaena has a higher NDF content than sesbania. Thus, roughage breakdown will be lower in the leucaena-fed diet while particles will be broken down faster in the sesbania diets and move out of the rumen faster (Hobson and Jouany, 1988), thus liberating ruminal space for consumption of additional material.

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Slight improvements in roughage intake as a consequence of high protein in the supplemented diets is consistent with previous findings (Hennessy et al., 1983; Lusby and Wagner, 1986; Lee et al., 1988). The foliage diets provided higher intakes of digestible organic matter (DOMI) and protein than the unsupplemented diet. The increased energy intake as evidenced from DOMI could counterbalance energy release from tissues, thus reducing net tissue mobilisation or liveweight loss (Oldham and Smith, 1982). This might have enhanced growth but the growth differences between sesbania and leucaena, at least in the initial phase, can be attributed to the individual traits of the foliages. The efficiency of utilisation of absorbed amino acids is enhanced in diets containing readily fermentable carbohydrates (McRae et al., 1993) such as those containing sesbania. Sesbania has earlier been shown (Bonsi et al., 1995) to promote a higher propionate concentration in rumen fluid compared with leucaena or teff straw only diets. Propionate can spare gluconeogenesis from glucogenic amino acids such as valerate and isobutyrate (Kempton et al., 19781, which can thus be used for protein accretion. Sesbania and leucaena were coincidentally isonitrogenous. The superiority of sesbania compared with leucaena with regard to nitrogen balance (0.221, microbial protein synthesis (0.08) and growth rate (0.19) (42 days) might be related to their differences in degradation, tannins and amino acids. Leucaena has higher essential and non-essential amino acid concentrations than sesbania (Brown et al., 1987; Wanapat, 1990). The faster degradation of sesbania released greater quantities of rumen metabolites to enhance rumen microbial function and proliferation (Mackie and White, 1990). Leucaena has a higher tannin concentration than sesbania (Bonsi et al., 1995) and this might have caused the higher faecal nitrogen observed in the leucaena diet. Tannins bind proteins and reduce the efficiency of their utilisation post-ruminally (Woodward and Reed, 1989). In the study of Wiegand et al. (19941, fibre digestibilities and nitrogen balance declined with increasing levels of tannins in four sesbania accessions, which were attributed to complexing and inefficient utilisation post-ruminally. Apart from tannins, the role of mimosine cannot be ignored, since mimosine in the rumen of leucaena-fed animals has antimitotic activity (Tangendjaja et al., 1990), which can affect both microbial and host animal cells. This has adverse effects on feed utilisation and animal growth. Reynolds and Adediran (1987) and Adejumo and Ademosun (1991) observed depressed growth rates in West African sheep supplemented with leucaena. Ruminants fed a better quality diet tend to compensate through protein repletion and consequently high initial growth rates. On meeting body protein requirements, ruminants deposit more fat than protein; thus, efficiency of gain reduces tremendously in the later phase (E.R. Orskov, personal communication, 1994). The cottonseed cake and teff straw diets served as positive and negative controls, respectively. The inability of cottonseed cake to stimulate greater roughage intake and digestion, despite being high in nitrogen compared with the foliages, could be attributed to its high NDF and NDF-N levels. Cell wall content can account for rumen fill and is highly correlated with both rumination and chewing time among a wide range of forages (Van Soest, 1994). The consequence of this is depressed forage intake (Van Soest, 1994).

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In this study, the dominance in growth rate with the CSC diet was certainly not a function of superior intake or digestibility. The possibility of superior amino acid profile coupled with its excellent phosphorus concentration (Taylor, 19921, higher nitrogen consumption (Tables 3 and 5) and microbial protein supply (Table 5) post-ruminally might have enhanced the growth rates recorded. The very high urinary nitrogen loss associated with the CSC-containing diet was also seen in the study of Amaning-Kwarteng et al. (1986). The low nutrient intake that occurs when low quality roughages are fed alone cannot support growth. Sheep on the unsupplemented diet needed to mobilise energy and protein from the tissues, which might have led to the weight loss experienced in this trial and in others (Silva et al., 1989; Sarwatt, 1990). 4.2. Pattern of supply This aspect of the study was undertaken in order to exploit the superior kinetic characteristics of sesbania, aimed at obtaining greater ruminant growth. Synchronising the release of nutrients from both sesbania and the slowly fermenting roughage determined the additional treatments (evening or morning and evening offer) to the morning-only offer. No significant beneficial or detrimental effects were observed in this study in terms of intake, digestibility, stability in rumen fermentation or growth. The proportionate increase (0.15) in microbial nitrogen supply and efficiency by sheep fed sesbania in the evening compared with morning only cannot easily be explained. Providing only part of the optimum level of sesbania supplement in the morning for SESME sheep might not have been enough to stimulate microbial activity. This could have led to the decline in the rate of roughage degradation (Table 2) when sesbania was offered in two portions. Response to frequency of feeding is positively manifested during restricted feeding and in young animals (Gibson, 1981). Robinson and McQueen (1993) confirmed this assertion when they observed no beneficial effects on intake, milk yield or composition due to frequency of feeding. Aronen (1989) observed a positive effect on grass silage intake and liveweight gains in ruminants fed two times a day compared with single feeding while more stable rumen pH (Yun and Han, 19891, volatile fatty acids and ammonia nitrogen (Aronen, 1989) were observed when feed was offered more than once a day. Ward and Adams (1987) reported no effect of time of supplementation on voluntary forage intake. Howard et al. (1992) reported increased forage and total dry matter intakes, nitrogen intake, faecal nitrogen excretion and cyclical changes in pH when the supplement was offered at 08:OO h, but digestibilities of ADF and organic matter were higher when it was offered at 15:OOh. Feeding maize supplements on alternate days did not affect consumption of hay or total organic matter, particulate or liquid passage rates (Chase and Hibberd, 1989). Previous results on synchronisation trials are conflicting since the frequency of feeding may not be in concert with the pattern of nutrient supply (Gill, 1990). Herrera-Saldana et al. (1990) found a 0.26 increase in microbial growth efficiency while microbial protein flow at the duodenum tended to increase (Sinclair et al., 1993). Satter et al. (1983) did not register an increase in the efficiency of nitrogen utilisation. The lack

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23

effect of feeding frequency on ruminal turnover rates and volume in the study of Yang and Varga (1989) agrees with the results of this study.

of

5. Conclusion

The important role of supplements for higher growth through improved rumen environment has been confirmed. Future trials should investigate supply patterns vis-a-vis levels of inclusion and such assays should be broadened to include other foliages. It is recommended that farmers in the tropics can supplement with sesbania either in the morning or evening or both without any detrimental effects, provided that labour costs are negligible.

Acknowledgements

MLKB is grateful to the International Livestock Research Institute (ILRI) (formerly ILCA), Addis Ababa, Ethiopia for sponsoring this project. The assistance of Dr. David Anindo (Ag. Nutrition Laboratory Manager), the staff and workers of ILRI Sheep barn and Nutrition laboratory is highly appreciated. The secretarial assistance of Y. Mamo is well acknowledged.

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