In one experiment the effects of casein in the abomasum was compared to isonitrogenous quantities of casein or urea in the rumen. In another two experiments the effects of casein in the rumen or abomasum were compared to isocaloric quantities of glucose or starch or to treatments where casein was partially replaced by these carbohydrates. Casein and glucose or starch were administered to the rumen or abomasum twice daily as pulse doses in quantities varying between 30 and 80 g per day. Measurements include voluntary intake of hay, ADG, wool growth, non-ammonia N (NAN) flow to the abomasum, and N-retention. Results suggest that supplementation with casein instead of NPN in the rumen may be beneficial. Secondly, postruminal administration of casein increased ADG, wool growth and, on occasion, hay intake. Postruminal administered casein furthermore, increased NANflow to the abomasum and N-retention. Thirdly, glucose or starch supplementation to the rumen or abomasum alone was not beneficial in terms of ADG, wool growth and N retention. It is concluded that indispensable amino acids at the tissue level of sheep are limiting with such forages, rather than energy – a fact which should be taken into account with supplementation in practice.