The feed intake of grazing cattle. II. The influence of size of animal on feed intake

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Abstract
1. Two experiments each with 3 dry cows, 3 heifers and 3 calves were carried out in 1959 and 1960 under uniform continuous grazing conditions on a ryegrass-white clover sward to measure individual feed intake by the chromic oxide-faecal nitrogen method. 2. Estimates of digestibility were high (70–82% in organic matter) and there was evidence that calves selected a diet of higher digestibility than cows. 3. Mean daily estimates of organic matter intake were for cows (1300 lb. live-weight) 23·5 lb., for heifers (790 lb. live-weight) 20·8 lb. and for calves (450 lb. live-weight) 14·3 lb. Corresponding digestible organic matter intakes were 17·4, 15·3 and 11·0 lb. 4. Relationships between digestible organic matter intake and liveweight were calculated and the merits of the exponents 0·62 and 0·73 of liveweight discussed. 5. The results were compared with accepted cow equivalent standards and, regardless of the exponent chosen, agreed with the system which adopts higher values for young grazing cattle.