A note on the effects of dietary protein degradability in the rumen on the voluntary intake and digestibility of barley straw by lactating beef cows

Abstract

In a previous experiment with pregnant beef cows (Alawa, Fishwick, Parkins, Hemingway and Aitchison, 1986) when equal amounts of crude protein (CP) were supplied from a range of concentrates providing different amounts of rumen-degraded protein (RDP), the voluntary intake of barley straw dry matter (DM) and the metabolizable energy (ME) obtained from straw were positively and significantly correlated with the intake of RDP. Whilst increasing proportions of rumen-undegraded protein (UDP) have been shown to increase the milk yield of ewes (Robinson, McHattie, Calderon Cortes and Thompson, 1979) the response of lactating beef suckler cows to UDP in terms of milk yield is not clear. There is an increasing interest in the use of peas as a protein supplement but they have not been compared with more conventional protein sources. Accordingly these present experiments were conducted to study the response of lactating beef cows and their calves to proteins from different sources providing different amounts of RDP and UDP.