Abstract
A group of 24 male and female crossbred Holstein calves were rotationally grazed for 180 days on 1·94 ha of 28 -day old Pangola pastures. Half received 1·36 and half 2·04kg meal supplement per day. The botanical and chemical composition of the pastures were determined, and intakes of organic matter and nutrients by the ca lves were estirnated by using herbage sampling before and after grazing and by using an inert marker, chromic oxide, in two trials. Seventy to 75 per cent of the herbage was Pangola grass. The herbage dry matter contained 7·4 to 8·2 per cent crude protein, 29·9 to 34·9 per cent crude fibre, 1.5 to 2·5 per cent ether extract, 9·5 to 11.1 per cent ash and 46·0 to 49·8 percent nitrogen-free extractives. The in vitro digestibility of the dry matter was 51.7 to 57.4 per cent on average during grazing rotations 3 to 8. From cut herbage samples it was estimated that an average of 40 per cent of the available herbage was eaten, each calf getting 4·5 kg/day. From the chromic oxide: faecal dry matter ratios and in vitro digestibilities it was estimated, in trial 2, that calves ate 5·2 kg dry matter per day. The rectal grab sampling of faecal output in trial 1 gave a much less accurate estimate than direct sampling from dung pats. It was calculated that the total diet, at both levels of meal supplementation was adequate with respect to protein but not always with respect to energy.
