Promising tropical grasses and legumes as feed resources in Central Tanzania IV. Effect of feeding level on digestibility and voluntary intake of four herbaceous legumes by sheep

Abstract

An experiment involving comparison of 4 legumes fed at 5 levels was conducted to study the effect of the level of feeding on digestibility and voluntary intake by Blackhead persian rams. The legumes were Neonotonia wightii cv. Mpwapwa (NWM), Stylosanthes scabra cv. Seca (SSS), Macrotyloma axillare cv. Archer (MAA) and Macroptilium atropurpureum cv. Siratro (MAS). The forages were cut at 8 weeks and dried in the sun. Sixteen sheep were used and fed 600, 900, 1200, 1500 and 1800 g/day in a split plot design. Among the species compared, SSS and NWM had higher ( P < 0.05) organic matter (OM) digestibility than MAA and MAS. Differences in intakes among species were observed, with MAS having lower OM intakes ( P < 0.05) than the other species. Increasing feeding level allowed the selection of more leafy diet with significant improvement ( P < 0.05) in OMD in SSS, and MAA, but not of MAS and NWM. Significant improvement ( P < 0.05) in intakes of OM and digestible OM were observed in all species, as feeding level was raised from 600–1800 g per day, to allow for the selection. The level of feeding allowing maximum intakes of OM with the least refusal was, on the average, 1200 g with 19.6% refusals, ranging from 900 g per day with refusals of 10.3% for MAS, to 1500 g per day with refusals of 29.4% for SSS. The maximum OM intakes were 20.5 g kgW −1 d −1 and 25.5 g/kg BW/day for MAS and SSS, respectively. Estimated maximum intake at infinite feeding level was, on the average, 26 g/kg BW/day. A realistic value for SSS could not be obtained, but was, probably, considerably higher than that for the others. To obtain a maximum value for animal production, refusals of approximately 40% would be required. Among the legumes studied, SSS seems to be the most promising species for the semiarid areas of Central Tanzania.