Assessment of preference and intake of browse species by Yankasa sheep at Shika, Nigeria

Small Ruminant Research 42 (2001) 203±210

Assessment of preference and intake of browse species by Yankasa sheep at Shika, Nigeria A.T. Omokanye*, R.O. Balogun1, O.S. Onifade2, R.A. Afolayan3, M.E. Olayemi1 National Animal Production Research Institute (NAPRI), Shika, Zaria, Nigeria Accepted 8 June 2001

Abstract Two experiments involving different browse species were carried out during the early dry season in an area of subhumid Nigeria with adult Yankasa sheep. Experiment 1 involved preference studies of nine browse species offered simultaneously in different post-harvest treatments (fresh, wilted or dried state). Experiment 2 determined the short-term intake rate of top four browse species from Experiment 1 offered in two forms (unchopped versus chopped) as either fresh or sun-dried material. In Experiment 1, fresh material was most preferred, followed by wilted and sun-dried material. The overall order of preference of the ®rst four browse species accepted by sheep were: Cajanus cajan, Gmelina arborea, Leucaena leucocephala and Adenodolichos paniculatus. Based on mean dietary preference across the three post-harvest treatments, Khaya senegalensis and Gliricidia sepuim were completely rejected by sheep. Experiment 2 mean dry matter (DM) intake rate was highest (34 g DM/kg LW0.75 h 1) for L. leucocephala and least (6 g DM/kg LW0.75 h 1) for A. paniculatus. Fresh material was consumed more readily than dried (24 versus 10 g DM/kg LW0.75 h 1). Chopping of browse species before offering enhanced intake by around 60%. As the study period progressed, the consumption of fresh and chopped materials remained moderately consistent, while those of dried and unchopped materials in turn increased gradually. Results from Experiment 2 were in agreement with observations from Experiment 1, particularly in terms of order of preference of fresh materials, which matched animals' relative short-term intake. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Browse; Preference; Post-harvest treatments; Intake; Sheep

1. Introduction

*

Corresponding author. Present address: Centre for Farming Systems Research, University of Western Sydney, Locked Bag No. 1797, Penrith South DC 1797, NSW, Australia. Tel.: ‡61-2-4570-1135; fax: ‡61-2-4570-1684. E-mail address: [email protected] (A.T. Omokanye). 1 Present address: Division of Animal Science, University of New England, Armidale, NSW, Australia. 2 Present address: Department of Pasture and Range Management, University of Agriculture, Abeokuta, Nigeria. 3 Present address: Department of Animal Science, The University of Adelaide, Roseworthy, SA, Australia.

In the drier northern parts of Nigeria, where most of the ruminants are located, ®brous standing grass is the major fodder source during the dry season. During this period, herd owners try to vary the diet of stock by providing more-nutritious fodders (from browse, hay from leguminous crops, green regrowth in low-lying and/or burned areas). Among the better fodders, browse ranks ®rst; leaves, ¯owers and fruits of many trees and shrubs are readily consumed (Leeuw, 1975). They are less susceptible to climatic ¯uctuations and provide green foliage biomass of high digestibility and

0921-4488/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 4 8 8 ( 0 1 ) 0 0 2 5 0 - 4

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protein content when most forage resources are low in nitrogen content. Furthermore, 35% of the animal digestible crude protein (CP) requirements of cattle in semi-arid Nigeria comes from browse, with a peak of 80% in the dry season (Bayer et al., 1987). Generally, in Nigeria, cut and carry systems of using browse are common in many areas. However, for good performance of the animals their acceptability, intake, digestibility, nutrient value and utilisation are important factors to be considered (Kenny and Black, 1984). In a number of studies, post-harvest treatments to multipurpose trees and shrubs, pasture grass and legumes, and their effect on acceptability and intake have been assessed (Kenny and Black, 1984; Palmer and Schlink, 1992; Raa¯aub and Lascano, 1995). Information on preference of browse species by sheep and goats in subhumid Nigeria is lacking. Recently, Olayemi et al. (1998) reported that Khaya senegalensis, Adenodolichos paniculatus, and Gmelina arborea were the most selected browse species by goats during the later parts of early dry season. It was suggested that the materials should be wilted or sun-dried before being feed to the animals. The present study evaluated the relative acceptability and/or intake of browse species as forage for sheep. The most recently introduced browse species to Shika is Cratylia argentea. Observations between 1992 and 1994, in a screening trial involving several forage species showed that the browse legume C. argentea had good establishment, vigorous growth after defoliation, profuse ¯owering and was well suited to the environment (Omokanye et al., 1998). Some of these browse species are native to the savannah environments (e.g. A. paniculatus, Desmodium velutinum and Sphenostylis schweinfurthii), while some have been established (e.g. Leucaena leucocephala, G. arborea) after several decades of introduction into Nigeria. Gliricidia sepium is native to western Nigeria. 2. Materials and methods Two experiments were conducted at the National Animal Production Research Institute (NAPRI) premises located at Shika (118120 N; 78330 E) between October and November 1997. The vegetation is typically Northern Guinea Savannah and the zone has

one (unimodal) wet season which begins in April/May, stabilises by June and ®nishes by mid-October. The mean long-term annual rainfall (1985±1997) was 1008 mm. Mean maximum temperature varies between 27 and 35 8C, depending on the season. Kowal (1968) described the physical properties of the soil as well-drained sandy loam soil with a clay fraction consisting mainly of kaolinite and small quantities of illite de®cient in N and P. 2.1. Experiment 1: preference of browse species by group-fed sheep The aim of this experiment was to evaluate the relative preference (Hodgson, 1982) of nine browse species as forage for sheep. Twelve adult Yankasa sheep (six rams and six non-pregnant ewes) averaging 26.9 kg were used. Browse species were grown at NAPRI, except for G. arborea, K. senegalensis and D. velutinum which were sampled from the range roadsides. At the time of the experiment, browse species L. leucocephala, Cajanus cajan, C. argentea and Gliricidia sepuim had been established for approximately 5 years. A. paniculatus and S. schweinfurthii had been established for about 15 years, with fresh regrowth occurring every year. All the browse species were offered as (1) freshly cut (within 60 min of harvest); (2) wilted after harvest (for 24 h under shade); and (3) sun-dried (for at least 5 days) forages, in 30 min tests in the morning before 10:00 h for 4 days each, for a total experimental period of 12 days. The animals were fasted overnight. All the nine feeds were placed side by side in wooden troughs of 1 m …width†  9 m …length†  0:3 m (height) in dimension. The trough was partitioned into nine compartments. Prior to data collection, animals were allowed free access to each form of offer for 1.5 h a day (between 9 and 10:00 h) and then the animals released to graze, lasting for a period of 3 days each, with all the nine browse species presented at once. Before the experiment, L. leucocephala was occasionally cut and carried to the entire ¯ock of sheep available within NAPRI premises. The sheep had no previous experience of the other eight browse species. However, the sheep might have come in contact with A. paniculatus, D. velutinum and S. schweinfurthii in their grazing paddocks, because these are native to the environment.

A.T. Omokanye et al. / Small Ruminant Research 42 (2001) 203±210

The grazing paddocks contained mixtures of forage species. None of the browse species had thorns or other forms of physical plant defence. Two sets of the nine browse species, arranged in troughs, were available on each day and these were offered concurrently to each group of six rams and six ewes. The two groups of animals were housed separately. Each browse was weighed before and after the test and, the difference indicated the amount eaten by each group of sheep. Before the experiment, and after feeding on the test species on each day, the animals were offered concentrate feed before being released with other animals to graze. The starting positions of the troughs were rearranged in a predetermined order after an interval of 15 min. Based on the results obtained during acclimatisation, the test species were offered in excess to maximise animals selectivity and minimise effects of resource depletion. Dry matter (DM) contents of fresh, wilted and sun-dried materials were as follows: 46, 57 and 78% DM (L. leucocephala), 54, 61 and 73% DM (C. cajan), 43, 54 and 80% DM (C. argentea) and 35, 51 and 86% (G. sepuim), 48, 56 and 67% DM (G. arborea), 28, 43 and 84% DM (K. senegalensis), 52, 66 and 78% DM (D. velutinum), 48, 55 and 63% DM (A. paniculatus) and 53, 68 and 79% DM (S. schweinfurthii). Dietary preference index was calculated as feed intake divided by amount of feed offered. Based on the dietary preference index obtained, each browse was classi®ed into one of the following ®ve preference classes: (1) 0.76±1.00, high preference (hp); (2) 0.56±0.75, moderate preference (mp); (3) 0.45±0.55, fair preference (fp); (4) 0.26±0.44, poor preference (pp); and (5) <0.26, no preference (np). The mathematical mode used for the analysis of data included ®xed effect due to nine browse species, three post-harvest treatments and sex groups (rams and ewes), and residual error. For forage analysis for proximate composition, a known amount of each browse species was taken on days 1 and 4 (for fresh), 5 and 8 (for wilted) and 9 and 12 (sun-dried) of the trial. The samples were oven dried at 70 8C for 48 h, re-weighed for determination of DM. Sub-samples were then taken and ground with Christy and Norris Laboratory mill using a 1 mm mesh. These were subsequently analysed for ash, ether extract (EE), crude ®bre (CF) and nitrogen (N) by standard methods (AOAC, 1990). CP was calculated as %N  6:25.

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2.2. Experiment 2: short-term intake by individual sheep The aim of this second experiment was to investigate if the rate of intake of freely accessible browse by hungry sheep varied between feeds and whether there was an in¯uence from changing the form in which it was presented, e.g. cutting into pieces, offered as fresh or dried. The best four browse species emanating from Experiment 1 formed the basis of this second experiment. These species were offered either as fresh (within 60 min of harvest) or sun-dried (for at least 5 days) to two different groups of six adult Yankasa rams (weighing 25.7±27.3 kg and ages between 1.8 and 2 years) for 1 h to determine short-term intake rate. The browse species were offered simultaneously as chopped (2±4 cm pieces) and unchopped in different plastic bowl containers. Each browse species was examined for intake during a 4 days study period. The animals were put each morning into the individual pens at least 30 min before the start of the experiment and individually fed. Prior to data collection, animals were allowed free access to the test browse species for further acclimatisation for at least 3 h a day for 5 days. The test period for data collection was 1 h and the materials were offered as Days Days Days Days

1, 2, 3, 4,

5, 6, 7, 8,

9 and 13 10 and 14 11 and 15 12 and 16

L. leucocephala G. arborea A. paniculatus C. cajan

The amount of test forages consumed was calculated by difference and results expressed as short-term DM intake per h corrected for metabolic liveweight of the animal (LW0.75, where LW is the liveweight of the animal in kg). After the measurements were made, the animals were given concentrate diets and then released for the day's grazing on mixed pastures. The L. leucocephala plant had fresh green leaves, profuse ¯owering and some young pod, while G. arborea had a few mature green leaves, many young leaves, profuse ¯owering and some pods. A. paniculatus on the other hand, contained old leaves, few new shoots from the base, few ¯owers and pods already getting mature. C. cajan had mainly green leaves, was

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a non-leguminous browse had the highest CP (26.7%) while S. schweinfurthii had the lowest CP (13.0%). The CF concentration varied from 7.9% for G. sepium to 37.9% for A. paniculatus. For EE and ash, the highest values were over 5 and 1.5 times, the lowest values, respectively. Table 2 shows stage of growth at the time of examination, calculated dietary preference index and preference classes of nine browse species offered to sheep at the same time in either fresh or wilted or sun-dried form. For materials offered as fresh, L. leucocephala was most selected followed by G. arborea, A. paniculatus and C. cajan in that order. Observations showed that the ¯owers of G. arborea and C. cajan pods were selected more from the forage materials than was the case for other browse with ¯owers. K. senegalensis and G. sepium were completely rejected. Of the materials selected, D. velutinum and S. schweinfurthii were least consumed. Dietary preference index of selected browse, therefore, varied from 0.03 for D. velutinum and S. schweinfurthii to 0.95 for L. leucocephala. Generally, the wilted browse was not as preferred as fresh browse. The preference for wilted browse decreased considerably when compared to fresh form. In wilted form, C. cajan, G. arborea and L. leucocephala were preferred in that order. Most of the browse species were rendered unsuitable by wilting. Dietary preference index was highest for C. cajan (0.74) followed by G. arborea (0.41) and L. leucocephala

¯owering profusely and had some young pods present. CP was analysed, following the procedures described for Experiment 1. The mathematical model included ®xed effect due to replicate, browse, post-harvest treatments, forms of feed on offer and corresponding interactions, and residual error (SAS, 1988). 3. Results 3.1. Experiment 1 The proximate composition of browse species fed to sheep is presented in Table 1. Surprisingly, G. arborea,

Table 1 Proximate composition (% DM) of browse species offered to sheep in a preference trial at Shika, Nigeria (Experiment 1)a Browse species

CP

CF

EE

Ash

L. leucocephala G. arborea C. cajan A. paniculatus D. velutinum C. argentea S. schweinfurthii G. sepuim K. senegalensis

21.3 26.7 18.7 14.9 23.4 21.1 13.0 23.7 19.5

18.2 20.5 28.3 37.9 N.A. 29.2 N.A. 7.9 N.A.

10.6 4.4 3.8 1.9 N.A. 2.0 N.A. 4.6 N.A.

7.9 10.0 7.2 7.1 N.A. 12.0 N.A. 7.1 N.A.

a

N.A.: not available.

Table 2 Dietary preference index, preference class and stage of growth of browse species offered to Yankasa sheep at Shika, Nigeria (Experiment 1) Browse species

Dietary preference index Fresh

C. cajan G. arborea L. leucocephala A. paniculatus C. argentea D. velutinum S. schweinfurthii G. sepuim K. senegalensis a

b

0.40 (pp) 0.93 (hp) 0.95 (hp) 0.49 (fp) 0.06 (np) 0.03 (np) 0.03 (np) ± (np) ± (np)

Wilted

Sun-dried

0.74 (mp) 0.41 (pp) 0.34 (pp) ± (np) ± (np) ± (np) ± (np) ± (np) ± (np)

0.93 (hp) ± (np) ± (np) ± (np) ± (np) ± (np) ± (np) ± (np) ± (np)

Overall rankinga

Stage of growth

1 2 3 4 5 6 7 8 8

Leaves green, flowers and pods present Mature leaves, young green leaves, mid-flowering, some pods Leaves green, early flowering, no pods Mature leaves, few new shoots, full bloom, pods present Leaves green, flowers and some young pods present Mature leaves, flowers and some mature pods Mature leaves, new shoots and no flowers or pods present Leaves green, no flowers and pod present Flush of new leaves, no flowers and pods present

Calculation based on percent DM of feed consumed across the post-harvest treatments. Values in parenthesis indicate preference classes (hp: high preference; fp: fair preference; mp: moderate preference; pp: poor preference; np: no preference). b

A.T. Omokanye et al. / Small Ruminant Research 42 (2001) 203±210

(0.34). Sun-drying the forages for about 5 days before assessing for preference resulted in the sheep completely rejecting all these browse species in favour of only C. cajan with an index of 0.93, thereby making it of highly dietary preference. On each trial day, observations showed that the animals would initially reject all the browse species by moving away from the trough on presentation, but would return a few seconds later and eat only C. cajan. The mean dietary preference index, when averaged over the three post-harvest treatments, was highest for C. cajan (0.69) and least for D. velutinum and S. schweinfurthii (0.03). The overall ranking of the nine browse species examined based on the mean dietary preference index was as follows: C. cajan, G. arborea, L. leucocephala, A. paniculatus, C. argentea, D. velutinum/S. schweinfurthii and G. sepium/K. senegalensis. 3.2. Experiment 2 The results on intake of chopped and unchopped browse offered simultaneously as fresh or dried materials for the four browse species examined are in Table 3. Intake rate on an `as offered basis' (forage consumed in 1 h) was signi®cantly affected by browse species, post-harvest treatments and form offered. Comparisons of the browse species across post-harvest treatments revealed that L. leucocephala was the most readily consumed browse with a mean intake rate of 34 g DM/kg LW0.75 h 1 and intake was lowest (6 g DM/kg LW0.75 h 1) for A. paniculatus.

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The average intake of fresh browse was higher (24 g DM/kg LW0.75 h 1) than when offered as dried (10 g DM/kg LW0.75 h 1). This shows that the intake of fresh as against dried browse was about 71%. L. leucocephala was completely rejected when dried, while intake of dried C. cajan was higher than other browse species under examination. The mean intake of fresh browse when pooled across unchopped and chopped materials was the same (34 g DM/kg LW0.75 h 1) for both L. leucocephala and G. arborea. The average intake was 16 g DM/kg LW0.75 h 1 for unchopped and 21 g DM/kg LW0.75 h 1 when the browse were cut into pieces. Generally, with browse  post-harvest treatments  form interaction (P < 0:01), the amount of any browse (except with sun-dried A. paniculatus) consumed was higher when chopped into pieces of between 2 and 4 cm long than unchopped materials. As shown in Fig. 1a, the intake of L. leucocephala and G. arborea by adult Yankasa sheep was fairly constant as the study period progressed. However, the intake of C. cajan, increased gradually as the feeding period increased, while the reverse was the case for A. paniculatus. The intake of unchopped and chopped materials did not vary widely, and there was a wider difference in consumption of fresh over the sun-dried materials with respect to days of feeding (Fig. 1b and c). However, the rate of intake gradually increased as the study period progressed. The browse species, L. leucocephala, G. arborea, A. paniculatus and C. cajan, had 19.6, 22.4, 12.7 and 19.3% CP, respectively.

Table 3 Short-term intake (g DM/kg LW0.75 h 1) by Yankasa sheep of unchopped and chopped browse fed either as fresh or sun-dried form at Shika, Nigeria (Experiment 2)a L. leucocephala

G. arborea

A. paniculatus

C. cajan

Unchopped Chopped Mean

Unchopped Chopped Mean

Unchopped Chopped Mean

Unchopped Chopped Mean

Treatment Fresh Sun-dried

25.1 ±

42.2 ±

34 ±

29.4 4.0

Mean

25.1 b

42.2 a

16.7 b 24.5 a

38.0 10.9

33.7 a 9.4 7.5 b 2.3

10.9 1.5

5.9

6.2

22.6 a

14.9 b

10.2 a 13.2 1.9 b 16.5

21.3 23.9

17.3 20.2

a Means within row (for a particular browse species) and within column (post-harvest treatments) with different letters differ signi®cantly at P < 0:05. LSD (P < 0:05) for browse treatment …a† ˆ 5:7; LSD (P < 0:05) for form (unchopped or chopped) …b† ˆ 3:9; LSD (P < 0:05) for browse species …c† ˆ 4:6; LSD (P < 0:05) for …a†  …b† interaction ˆ 6:9; LSD (P < 0:05) for …b†  …c† interaction ˆ 3:4; LSD (P < 0:05) for …a†  …c† interaction ˆ 7:7; LSD (P < 0:05) for …a†  …b†  …c† interaction ˆ 9:1.

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Fig. 1. The intake by adult Yankasa sheep of four browse species (a), offered in two forms (b), and in two states (c).

4. Discussion Based on the critical level of 10.88% CP (1.74% N in DM) for ruminants (NRC, 1976), all the browse species generally had high protein content. L. leucocephala and G. arborea contained proportionally more CP and less ®bre when compared with other browse on offer. However, whether or not these browse would also have a high digestibility to help

further in the prediction of diets selected by sheep needs to be examined. Results from this study showed that fresh materials were preferred to wilted or dried ones. This indicated that wilting and drying treatments imposed in this study were fairly severe, as these led to higher DM contents. It could be deduced that moisture content of browse on offer (when preferred by sheep) is a great determinant of acceptability. In a similar study with Red Sokoto goats in the same Institute,

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Olayemi et al. (1998) found that wilted browse was the most preferred in a series of post-harvest treatments considered. The overall ranking of browse preference on offer was as follows: C. cajan, G. arborea, L. leucocephala, A. paniculatus, C. argentea and D. velutinum/ S. schweinfurthii. Selection responses were demonstrated more by sheep to varying amounts of various plants components/parts. The availability of more ¯owers of G. arborea and C. cajan materials led to selection of these plants in preference to others (with the exception of L. leucocephala). In our study, K. senegalensis was completely rejected by sheep. Olayemi et al. (1998) found that this particular browse ranked ®rst in selection studies with goats. In fact, it was consumed almost completely in both wilted and sun-dried forms. Similar to this study, Karbo et al. (1993) and Olayemi et al. (1998) observed that G. sepium was completely rejected by sheep and goats, respectively. Importantly, G. sepium leaves have a characteristic smell which may make them unattractive to ruminants. Earlier reports indicated the presence of a potential toxic substance called coumarin (Anonymous, 1992) which changes to dicoumerol when the leaves are crushed. This could also contribute to its rejection. Dicoumerol is responsible for an antinutritional effect and is known to interfere with the normal blood clotting induced by Vitamin K. Preston and Leng (1987) earlier noted that unpalatable forage appears to give off volatile materials since animals reject it without tasting. Though C. argentea is the most recently introduced browse to the environment the sheep tended to prefer when fresh to K. senegalensis and G. sepium. Sheep particularly selected the ¯owers and tender twigs of this browse. Goats completely rejected C. argentea in any of the post-harvest treatments (Olayemi et al., 1998). Raa¯aub and Lascano (1995) observed low relative acceptability of C. argentea by sheep, particularly when fed immature forage, but not when the forage was mature, as in the present study. The merit of C. argentea is that it is free of tannins, but on the other hand has high protein degradability in the rumen (Aroeira and Xavier, 1990). In spite of high forage potential of C. argentea in subhumid Nigeria, further trials are needed on ways by which its utilisation by animals could be enhanced.

209

The results from this study showed that the intake rate of browse varies substantially by altering postharvest treatments and forms of offer. Our observations show that sheep do not spend an equal time eating a particular browse which was offered simultaneously as chopped and unchopped. Sheep relished the ¯owers (where present and visible) more than twigs, then leaves, young pods and stem in that order. There was further indication that deliberate preference was created for chopped browse as this can be eaten faster than unchopped material, when animals spend more time detaching plants' parts from the whole plant. The high intake of L. leucocephala in comparison to others may not be surprising. This is because the sheep used in this trial had presently been exposed to occasional fresh L. leucocephala forage before this trial. The forage was however, not being offered at a predetermined amount. However, an earlier study had indicated the bene®t of incorporating fresh L. leucocephala in the diet of Yankasa rams fed Hyperrhenia grass as the basal diet (Balogun and Otchere, 1995). Olayemi et al. (1998) however, reported low acceptability of L. leucocephala in a preference study with other six browse species presented to Red Sokoto goats in the same environment. The low acceptability reported by these workers may have been due to lack of previous experience or exposure with goats on L. leucocephala. It is generally known that ruminants on pasture tend to graze plants selectively that contain a high level of CP (Rutter et al., 1997). This may partly explain the order of preference (Experiment 1) by sheep of fresh L. leucocephala, G. arborea, C. cajan and A. paniculatus as being re¯ected in their CP contents. This study show that intake rate was particularly low when animals were fed dried browse, but not when the browse was fresh. This observation could simply be due to moisture reduction as the browse were wilted or sun-dried. The results here are similar to the ®ndings of Palmer and Schlink (1992) on Calliandra calothyrsus offered to sheep as fresh, wilted or dried material. However, Raa¯aub and Lascano (1995) and Olayemi et al. (1998) reported higher intakes resulting from dried browse as opposed to fresh. It can be suggested that post-harvest delays must be kept to the absolute minimum if maximum intake from L. leucocephala and G. arborea is to be achieved by

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sheep. The order of dietary preference of browse species when offered fresh emerging from Experiment 1 matched animals relative short-term intake in Experiment 2. Further research must look for ways of utilising the abundant native browse, particularly A. paniculatus. It is evident from this study that C. cajan was the only browse accepted by sheep when subjected to any of the post-harvest treatments examined. 5. Conclusions Forages offered as fresh were generally preferred over-wilted or sun-dried. C. cajan was selected when presented as fresh or wilted or sun-dried and thus, ranked ®rst across post-harvest treatments. Consequently, the intake rate of the fresh feeds was increased by cutting the species into pieces. L. leucocephala and G. arborea proved satisfactory as fresh materials. Acknowledgements The authors wish to thank Mr. S.A. Abubakar, Tasium Musa and Ashiru Ibrahim for their technical assistance without which this work could not have been carried out. We are most grateful to Dr. C.A.M. Lakpini, Programme Leader, Small Ruminant Research Programme, NAPRI for approving the use of the animals, and Mrs. Afusat Ibrahim for typing the manuscript. References Anonymous, 1992. Toxins from Gliricidia. In: Spore, Bi-monthly Bulletin of the Technical Centre for Agricultural and Rural Cooperation (CTA). Wageningen, The Netherlands, Vol. 39, p. 10. AOAC, Association of Of®cial Analytical Chemists, 1990. Of®cial Methods of Analysis, 15th Edition. Association of Of®cial Analytical Chemists, Washington, DC, USA, pp. 69±88. Aroeira, L.J.M., Xavier, D.F., 1990. Digestibilidade e degradabilidade da Cratylia ¯oribunda no rumen. Pasturars Tropicales 13, 15±19. Balogun, R.O., Otchere, E.O., 1995. Effect of level of Leucaena leucocephala in the diet on feed intake, growth and feed ef®ciency of Yankasa rams. Trop. Grassl. 26, 58±71. Bayer, W., Suleiman, H., Kaufmann, R., Waters-Bayer, A., 1987. Resources used and strategies for development for development

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