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

Abstract

An experiment was conducted to study the effect of increasing feeding level on digestibility and voluntary intake of four high yielding grasses cut at 6 and 10 weeks. The grasses were fed to Blackhead Persian rams (mean age = 72 weeks; mean weight = 30 kg) at levels of 600, 900, 1200, 1500 and 1800 g of hay per day in a split plot design. The grasses were Cenchrus ciliaris cv. Biloela (CCB), C. ciliaris cv. Gayndah (CCG), Panicum coloratum cv. Bambatsi (PCB) and Chloris gayana cv. Mpwapwa (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 CGM ( 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 digestibility 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 grasses selectively in favour of the more nutritious parts when offered excess feed. With higher feeding levels, OM digestibility, but not NDF digestibility, was significantly improved ( P < 0.05). Voluntary intakes of all species and stages were also improved by increasing feeding levels ( P < 0.05). The lowest levels of feeding, allowing maximum intakes of the hays, varied between species and stages of maturity. These feeding levels ranged from 900–1500 g of hay per day with refusals between 15.3–50.8% for PCB (6 weeks) and CGM (10 weeks), respectively. From calculations of optimal feeding levels to attain maximum daily nutrient uptake by producing sheep, we recommend early harvesting and feeding of the grasses at levels allowing refusals of at least 30%.