Ruminant performance is related to food intake which in turn depends on the diet dry-matter (DM) intake and on its energy concentration. Under intensive farming conditions dietary metabolizable energy ZME) concentration may be increased by manipulating the forage concentrate ratio or by adding lipid. The high energy content and high digestibility of lipids favours their use although caution should be taken to prevent adverse inhibition of rumen fermentation. It has been suggested that whold cottonseeds (WCS) a commonn oil seed grown in Israel and other countries with subtropical climates can be safely integrated into ruminant diets at a level of proportionately 0.25 of the dry-matter. Besides high content of energy WCS has a high content of crude protein and fibre. In warm regions the feeding of WCS may by of further advantage due to its high lipid content and associated low heat increment. However when WCS was offered to sheep as part of a diet given at the maintenance level no decrease in heat production was noticed. Since this could have been due to the high energetic efficiency of animals at the maintenance level the effect of feeding level on heat production in WCS-fed sheep was studied in the present experiment.