The effect of species of grass, stage of maturity and level of intake on the degradation of protein and organic matter in the rumen of steers

Abstract

Six Friesian steers (300 kg liveweight) were prepared with rumen and abomasal cannulae, and fed three artificially dried grasses at three levels of organic matter (OM) intake and at two stages of maturity. The grasses were paspalum (Paspalum dilatatum), oats (Avena sativa) and kikuyu (Pennisetum clandestinum). The apparent digestion of organic matter (OM) in the whole tract decreased with increasing maturity for all grasses. The proportion of OM digested in the rumen was greater for paspalum and kikuyu than oats, and increased with advancing maturity for paspalum and kikuyu. Microbial nitrogen flow from the rumen was 26 and 25 g/kg of OM apparently digested in the rumen for paspalum, 32 and 36 for oats and 25 and 14 for the early and late maturity kikuyu. The true degradation of grass protein in the rumen was between 0.70 and 0.80 for all three grasses, at all three feed intakes and for both stages of maturity of the grasses. Total rumen pool size was less for oats than paspalum or kikuyu. The retention time of particles and fluid in the rumen increased with decreasing feed intake for oats.