Voluntary intake of hay by steers was measured when supplements of barley were given: (1) whole unprocessed, (2) NaOH treated, (3) torrified (infra-red heat treatment), (4) crimped, (5) rolled, (6) ground and (7) ground and pelleted. The cereal supplements were given at 50 g/kg live weight0·75/day. The voluntary intakes of hay dry matter were 42·1, 43·0, 38·1, 35·1, 34·9, 34·4 and 30·5 g/kg W0·75/day respectively.
Dry-matter digestibilities of barley given without hay were (g/kg): whole, 672; NaOH treated, 807; torrified, 813 and rolled, 834.
Incubation of feed samples in the rumen in polyester bags showed that rolled barley disappeared much more rapidly than NaOH treated and torrified barley.
It is concluded that the deleterious effect of a cereal based supplement on rate of digestion of cellulose and consequently voluntary intake can be largely overcome by use of processing methods which reduce the rate of release of starch and yet ensure complete digestion. Treatment with NaOH looks promising in this respect.