Sheep were given artificially dried grass either in the long form or as pellets, and their energy retention measured. Experiments were made both at the maintenance level of feeding and when feed was offered ad libitum. An analysis of the effects of preceding and current daily feed consumption on heat production was made and both exact and approximate methods of estimating the mean food intake to which a determination of heat production should be referred, are given. Pelleting the dried grass increased voluntary intake of dry matter by 27%, and the intake above maintenance by 59% The metabolizable energy of the grass was depressed by pelleting but the net availability of metabolizable energy for production was 52% for pellets and 40% for long material. The percentage of the gross energy supplied above maintenance which was retained was 28% greater for pellets than for long dried grass. The results show that energy retention of the sheep was almost doubled when the grass was pelleted.