PROMISING TROPICAL GRASSES AND LEGUMES AS FEED RESOURCES IN CENTRAL TANZANIA III - EFFECT OF FEEDING LEVEL ON DIGESTIBILITY AND VOLUNTARY INTAKE OF 4 GRASSES BY SHEEP

An experiment was conducted to study the effect of increasing feeding level on digestibility and voluntary intake of four high yielding gras ses cut at 6 and 10 weeks. The grasses were fed to Blackhead Persian r ams (mean age = 72 weeks mean weight = 30 kg) at levels of 600, 900, 1 200, 1500 and 1800 g of hay per day in a split plot design. The grasse s were Cenchrus ciliaris cv. Biloela (CCB), C. ciliaris cv. Gayndah (C CG), Panicum coloratum cv. Bambatsi (PCB) and Chloris gayana cv. Mpwap wa (CGM). In vivo organic matter (OM) digestibility was on average 60% . Among the species compared, CCB and PCB had lower OM digestibility, by 3 units, than CCG and CCM (P < 0.05), but CGM had lower intakes (P < 0.05) than the other species by approximately 20%. Samples taken at 10 weeks regrowth had higher neutral detergent fibre (NDF) and lignin contents and lower protein contents and in vitro organic matter digest ibility compared to the 6-week cuts. Intake of OM, but not of NDF was also lower (P < 0.05) for the 10-week cut. The sheep consumed the gras ses selectively in favour of the more nutritious parts when offered ex cess feed. With higher feeding levels, OM digestibility, but not NDF d igestibility, was significantly improved(P < 0.05). Voluntary intakes of all species and stages were also improved by increasing feeding lev els (P < 0.05). The lowest levels of feeding, allowing maximum intakes of the hays, varied between species and stages of maturity. These fee ding levels ranged from 900-1500 g of hav per day with refusals betwee n 15.3-50.8% for PCB (6 weeks) and CGM (10 weeks), respectively. From calculations of optimal feeding levels to attain maximum daily nutrien t uptake by producing sheep, we recommend early harvesting and feeding of the grasses at levels allowing refusals of at least 30%. (C) 1998 Elsevier Science B.V.