Effects of supplementation with foliages of selected multipurpose trees, their mixtures or wheat bran on feed intake, plasma enzyme activities, live weight and scrotal circumference gains in Menz sheep

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Abstract

The experiment was conducted at Debre Zeit Research Station of the International Livestock Research Institute in Ethiopia for 126 days. Fifty-four male Menz sheep with initial live weight (LW) of 15.7±0.32 kg (mean±S.D.) were blocked on initial LW and randomly assigned to one of the nine treatments, giving six animals per treatment. The basal feed used in the experiment was tef (Eragrostis tef) straw. The supplement treatments consisted of wheat bran (positive control) or dried foliage of the multipurpose trees (MPT), Sesbania sesban 1198, S. sesban 15019, Acacia angustissima 15132, and Leucaena pallida 14203, or the mixtures of S. sesban 1198 and S. sesban 15019 with either L. pallida 14203 or A. angustissima 15132 at a ratio of 2:1. The level of supplementation was at 0.9% of LW on dry matter (DM) basis. The objectives of the experiment were to evaluate the effects of supplementation on feed intake, plasma activities of certain enzymes, daily LW and scrotal circumference gains. The crude protein (CP) content in the MPT leaves and their mixtures ranged between 21.6% and 27.8% of DM. Supplementation with mixtures of MPTs promoted higher organic matter (OM) (P<0.01), supplement and total DM (P<0.001) intakes and higher feed conversion efficiency (FCE) (P<0.001) than sole MPTs. Mixtures of MPTs also promoted higher (P<0.05) daily LW and scrotal circumference gains than wheat bran or sole MPTs. Plasma activities of alanine aminotransferase (ALT), γ-glutamyl transpeptidase (γ-GT), and aspartate aminotransferase (AST) were not different (P>0.05) between treatments at the beginning and at the end of the experiment. It is concluded that supplementation with mixtures of MPTs promoted better utilization of nutrients and animal performance compared to sole MPTs or wheat bran in sheep fed on a basal diet of tef straw.

Introduction

Multipurpose trees (MPTs) are widely used as protein supplements to animals maintained on low quality feeds in tropical smallholder farming systems. Supplementation with MPTs is mainly meant to correct deficiencies of nutrients like nitrogen (N) and sulfur (Egan, 1986). Alleviation of these deficiencies improves degradation of fibrous feeds in the rumen and the animals' metabolic capacity to use energy, both of which increase the voluntary intake of digestible organic matter (DOM) and animal production (Goodchild and McMeniman, 1994). Despite differences in rumen degradability characteristics Kaitho, 1997, Siaw et al., 1993, MPTs in the genera Sesbania and Leucaena were reported to improve the intake of DOM when supplemented to sheep fed tef straw (Umunna et al., 1995).

However, animals feeding on foliages of some MPTs may encounter adverse effects in terms of feed intake, digestibility and metabolic functions due to effects that arise from commonly occurring secondary plant metabolites contained in the MPTs D'Mello, 1992, Kumar and Singh, 1984. A good example of such effects is the mortality observed in sheep supplemented with Acacia angustissima 15132 without gradual adaptation (Odenyo et al., 1997). Animals minimize the deleterious effects of tannins or other plant secondary compounds by feeding on mixtures of plant species under natural grazing conditions (Dicko and Sikena, 1992). Le Houérou (1980) also reported that consumption of mixed shrubs was higher than that of single species under range browsing situations. These may lead to the suggestion that supplementing MPTs to animals as mixtures could dilute the negative effects of tannins and other secondary plant metabolites contained in them. Topps (1992) also suggested the most practical alternative to dilute the effect of secondary plant metabolites in MPTs is to use them as supplements at low levels in a suitable mixture, or to feed them as a combination of two or more rather than one MPT species. Indeed, Madsen et al. (1997) remarked that the nutritive value of a certain feed is influenced by the composition of the total ration in which it is fed, and usually, mixtures of feeds will allow for maximization of benefits drawn from each component. However, most experiments conducted on the supplementation of MPTs to animals fed poor quality roughages did not employ the mixture strategy. The use of the mixture strategy could possibly dilute the effects of antinutritional constituents limiting the utilization of some of the MPTs, and/or could harness and maximize the utilization of nutrients contained in the MPTs for improved animal performance. Therefore, this study was conducted with the objectives of evaluating the effects of supplementation with sole or mixtures of selected MPTs on feed nutrients intake, daily live weight (LW) and scrotal circumference gains, and levels of certain plasma enzymes in Menz sheep.

Section snippets

Site of study

The research was conducted at the International Livestock Research Institute's Debre Zeit Research Station, which is situated in the central highlands of Ethiopia at 38°58′E, 8°44′N with an elevation of 1850 m above sea level.

Preparation of treatment feeds

The MPT leaf supplements were harvested from the trees grown on the research farm at Debre Zeit Research Station. The fresh leaves were spread on plastic sheets and dried in a shade for 4–5 days, and were then packed in polythene sacks and stored for later use. The basal

Chemical composition of treatment feeds

CP in all the MPTs and their mixtures ranged between 21.6% and 27.8%, and the CP in wheat bran was 16.5% (Table 2). OM and fiber in the MPTs ranged between 88.4–93.1% and 20.4–33.8%, respectively. The highest levels of OM, CP, NDF, ADF and NDF-N and the lowest levels of ash were observed in A. angustissima 15132. ADL was highest in L. pallida 14203. Both S. sesban 1198 and S. sesban 15019 contained relatively lower OM, NDF, ADF, ADL and NDF-N, and higher ash than A. angustissima 15132 and L.

Chemical composition of treatment feeds

High CP content of the MPTs and their mixtures qualifies them as appropriate protein supplements to animals fed on a basal diet of tef straw, which is deficient in CP. However, high SP content in A. angustissima 15132, and FCT in L. pallida 14203 make these MPTs less desirable supplements compared with both accessions of S. sesban and their mixtures with the former MPTs.

Daily feed and nutrients intake

Higher daily basal feed DM intake in animals supplemented with sole or mixtures of MPTs than those supplemented with wheat

Conclusions

High level of SP in A. angustissima 15132 appear to have played a major role in reducing its palatability and thereby limiting daily feed intake and animal performance arising thereof. Moreover, consistent consumption of A. angustissima 15132 for 3–4 days at around 0.9% of LW on DM basis can lead to acute toxicity that may result in mortality of sheep. Such negative aspects of A. angustissima 15132 were offset when it was supplemented in mixture with both accessions of S. sesban resulting in

Acknowledgements

The first author is grateful to the German Academic Exchange Services (DAAD) for financial support to undertake Ph.D. studies at Humboldt University, Berlin, Germany and the International Livestock Research Institute for funding the research work at Debre Zeit Research Station.

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