Studies on the nutrition of ruminants. II. The effect of level of crude fibre in maize-based rations on the carcass composition of Friesian steers

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Abstract
Three groups of eight yearling Friesian steers were fed on pelleted diets containing ground barley straw, maize and soya bean meal, the percentages of straw in the diets being 10, 30 and 50 (treatments 1, 2 and 3). The crude protein level was adjusted to 12% in all diets on an air-dried basis. Daily live-weight gain for treatment 2 was 7% greater than for treatment 1, and 12% greater than for treatment 3. Voluntary feed intake was also greater in treatment 2, by 16% when compared with treatment 1 and 4% when compared with treatment 3. The efficiency of feed conversion decreased by 10% for each 20% increase in dietary straw level. Weight loss during lairage was greater on treatment 3, as were total gut fill and omasum weight. The bone content of carcasses was similar for all treatments; carcass lean was increased in treatment 2. Carcass and channel fat was severely depressed in treatment 3. The results are discussed in relation to dietary effects on carcass composition.