Multipurpose trees (MPTs) which are generally richer and maintain a higher nutrient quality than grasses throughout the year, constitute an important feed resource in ruminant nutrition. The tree and shrub legume forages are rich in most essential nutrients such as proteins and minerals and tend to be more digestible than grasses and crop residues [1] . According to [2] , browse plants are available in the off season but most of them are less beneficial to livestock as they contain antinutritional factors. Enterolobium cyclocarpum is a tropical multipurpose tree whose leaves contain the antinutritonal factor saponin [3] , tannins, phytate and oxalates [4] . It is a Central American native species that grows in central Mexico, from the Pacific Ocean coasts and the Gulf of Mexico to the North of Brazil and Columbia [5] . It has defaunating properties [6] and the heartwood extracts have dissuasive effects on termites [7] . In the south western Nigeria, Enterolobium cyclocarpum foliage has not been accepted by sheep, goats and cattle possibly due to the presence of antinutritional factors [2] .

Fermentation is one of the oldest applied biotechnologies, having been used in food processing and preservation as well as beverages production for over 6000 years [8] . Biological treatments of lignocellulosic substrates include cultivation with specific fungi capable of producing a spectrum of lignin and cellulose-degrading enzymes during solid state fermentation [9] . However, forage quality and overall potential are best measured in terms of animal productivity [10] . The purpose of this study was to appraise the effects of biodegrading Enterolobium cyclocarpum with Aspergillus niger on improving its utilization by WAD sheep.

The study was conducted at the Teaching and Research farm of the University of Ibadan, Ibadan. Leaves of Enterolobium cyclocarpum were obtained from an established plot in Wasimi village, South Western Nigeria. Sun dried leaves were ground, autoclaved and allowed to cool. A portion was saved for inoculation with Aspergillus niger. The fungi were grown on potato dextrose broth and harvested into ground damp autoclaved EC in sterile plastic bowls. At the end of incubation, samples were oven-dried. Biodegraded EC gave fishmeal-like aroma as against choking and peppery smell of ground dry undegraded EC. The smell of the autoclaved EC was also choking but less than undegraded oven-dried samples. Twelve male West African Dwarf sheep, average weight 9.9 kg and age 7 - 9 months were randomly assigned to four experimental treatment groups in a completely randomized design with three animals per treatment. Grass and concentrates (Table 1) were fed separately, with grass serving as basal ration. The sole grass diet was served, allowing 20% increase of dry matter consumed the previous day. Feed was offered twice daily (08.00 and 16.00 hrs) while animals were weighed once weekly. All

animals were quarantined before the feeding trial and had ad libitum access to water. The experiment lasted for 70 days (8 weeks). Ground dry samples of Guinea grass and other supplemental diets were analysed for their contents of Ca, Mg, K, Fe, P and CP (Nx 6.25) using methods of [11] . Data were analysed by the analysis of variance procedures of SAS [12] , results were expressed as means of three replicates. Significant differences were compared using the Duncan Multiple Range Test at P < 0.05.

The proximate composition of the experimental diets is presented in Table 2. The crude protein of the Guinea grass (4.43%) is relatively low compared to the biodergraded Enterolobium cyclocarpum (14.13%).

The crude protein content of the biodegraded EC diets being higher than that of the autoclaved EC diet suggest the improvement in contents by fungal action. Treatment with white-rot fungi increased the nutritive value of straw [13] [14] . Though autoclaving might have effect on materials, action of the fungus on the autoclaved EC may have resulted to increased protein. Wheat straw treated with Pleurotus ostreatus and Trametes versicolor had increased CP and decreased organic carbon and C/N ratio as compared with untreated wheat straw [9] . [15] reported reduced crude fibre, ether extract, crude protein, and acid detergent fibre and nitrogen content of Albizia, as a result of autoclaving. The NDF values of the biodegraded EC were higher suggesting breakdown of autoclaved fibre by fungus. The removal of lignin and/or hemicellulose can substantially increase the susceptibility of biomass to enzymatic hydrolysis [16] . It has been previously shown that white-rot fungi can degrade crop residues during solid state fermentation as a result of action by carbohydrases (Cellulases and xylanases) and oxidative ligninolytic enzymes including lignin peoxidases, manganese peroxidise and lacase [17] [18] . Intake of Guinea grass, other concentrates and live weight gains of the sheep are presented in Table 3. The growth rate of animals fed concentrates were significantly (P < 0.05) different from grass diets. Intake of Guinea grass was higher for sole-grass fed animals but not twice as much as consumed by animals on grass and concentrate diets. [10] reported that animals on sole grass diets consumed twice as much grass than animals on mixed grass legume. Sheep on biodegraded EC diets consumed more concentrate than those on control and autoclaved EC diets, respectively. The high consumption suggests the improved nutritional and sensory value of the feed resulting from biodegradation. On the other hand, the choking odour of autoclaved Enterolobium cyclocarpum may have affected its palatability, hence, its being less consumed. However, the animals on the autoclaved EC diets consumed more grass than others on concentrate.

Several reports indicate that supplementation of basal grass diets improves feed intake and liveweight gains [19] [20] . The liveweight changes in this study were higher for biodegraded EC diets but not significantly different from the grass diet which had least liveweight gain.

The costs of experimental diets are given in Table 4. Cost per Kg of feed was highest for control and least for guinea grass diet. However, cost per unit gain was highest for guinea grass diet (N 176.73) and least for biodegraded EC diet (N 72.62).

The supplementation of Guinea grass with concentrates improved the efficiency of utilization and agrees with reports of [21] and [15] . In this study, cost of production was evaluated as that would show returns on investment. Although animals on control diets had highest total feed cost followed by biodegraded EC, the cost per unit tells better how much of investment would translate into mutton. In that regard, it was cheaper to produce one kilogram of mutton using biodegraded EC, compared to control, autoclaved EC and grass diets, respectively. Similarly, less of the biodegraded EC diet is required to produce the same amount of gain when compared to control, autoclaved and Guinea grass based diets respectively.

Results suggest that inoculation of Enterolobium cyclocarpum with Aspergillus niger is effective in enhancing nutrient quality, increasing intakes and liveweight gain thereby making fungal biodegradation a simple and cheaper alternative in improving the use of MPTs as fodder for small ruminants.

The authors are most grateful to Professor O.M. Arigbede for the establishment of the Enterolobium cyclocarpum arboretum.