Three types of straw were used, a spring barley (variety Corgi) untreated (UC), ammonia-treated Corgi (AC) and an ammonia-treated winter wheat (variety Longbow) (AW). Each straw was included in a complete diet containing either 350 (L), 450 (M) or 550 (H) g/kg straw. The other principal ingredients were rolled barley, molassed sugar-beet pulp and fish meal. Hereford cross steers approximately 16 months old and weighing 350 kg live weight were given the diets ad libitum in both a main trial lasting 80 days, to assess intakes, live-weight gains and food efficiency, and in a subsidiary trial to measure in vivo apparent digestibility. The live-weight gains during 80 days for steers given the UC diet at L, M and H inclusion were 117, 102 and 0·70 kg/day respectively. The respective live-weight gains for AC were 1·32, 1·27 and 1 02 kg/day and for AW 1 ·26, 1 ·20 and 0·95 kg/day. While experimental comparisons were terminated at 80 days when the first steers were slaughtered, all except five with the lowest growth rate reached the target fat class for slaughter before 6 months on the diets. While differences in intake and performance between steers given the straws closely reflected differences in degradation characteristics determined by in sacco measurements, the increase in in vivo apparent digestibility between untreated (0·510) and treated (0·545) was small. It is concluded that a large proportion of high quality or treated straw can be incorporated and utilized in diets for finishing cattle.
- food intake