Factors Which Influence the Requirements for Protein and Energy in Ruminants

The studies reported in this thesis were part of a continuing study on the effects of supplementation of low protein diets with proteins that escape ruminal fermentation. A basal diet of oaten chaff fed to lambs, was supplemented with casein, formaldehyde treated casein (FC) or FC plus urea. Voluntary feed intake and liveweight change of lambs was measured over a 105 d period. Feed intake, liveweight gain, wool growth and feed conversion efficiency was increased by the addition of treated casein. Urea plus treated casein did not improve responses above that obtained by treated casein. Provision of a soluble protein source (untreated casein) did not increase feed intake, liveweight gain or feed conversion efficiency. A second feeding trial using lambs fed a basal diet of oaten chaff, showed that supplementation with 100 g lupins, either untreated or treated with formaldehyde, did not produce greater growth responses or feed conversion efficiencies than did supplementation with 10 g urea. Lambs fed a basal diet of cottonseed hulls increased their liveweight gain, feed conversion efficiency and wool growth when supplemented with formaldehyde treated casein. Lambs fed cottonseed hulls as the basal diet had nil or very low protozoa populations in their rumen. Supplementation with sodium propionate or sodium acetate had no effect on liveweight gain, feed conversion efficiency or wool growth. No differences in glucose entry rates or acetate clearance was found in lambs fed cottonseed hulls as the basal diet and supplemented with formaldehyde treated casein, sodium propionate or sodium acetate