The nutrition of the veal calf. 4. The effect of offering roughage on health and performance.

Abstract

1. Eighteen bull calves, comprising twelve Ayrshires, three Friesians and three Jerseys were reared from birth to a slaughter weight equivalent to 22 % of mature cow weight of the breed.2. All the calves were given a milk substitute diet ad lib. in two feeds daily. Six of the calves received this diet alone and the remaining twelve calves were offered roughage ad lib. from I week of age, either as meadow hay or as barley straw. The calf-house was maintained at a mean temperature of 23' and a mean relative humidity of 62 %.3. The mean total intake of meadow hay and barley straw over the experimental period of about 12 weeks was 3.0 kg and 0.4 kg respectively. Only three calves were consuming any meadow hay and only two calves any barley straw at 7 weeks of age.4. The roughage consumed had no effect on the incidence of diarrhoea, on dry-matter intake from milk or on live-weight gain. All the calves offered meadow hay had lung lesions at slaughter. Severity of lung lesions in the Jersey and Friesian calves combined, but not in the Ayrshires, tended to be inversely related to the relative humidity to which they were exposed.5. Dressed carcass weight and killing out percentage tended to be lower for the calves offered meadow hay. There was a highly significant inverse relationship between total intake of hay and killing out percentage. Perirenal fat depositionin relation to carcass weight was significantly lower and carotenoid content of the fat significantly higher for the calves offered the meadow hay. Skin weight per unit of slaughter weight 0.78 or carcass weight OJ* was significantly greater for the calves given the milk substitute diet only.6. It is concluded that the calf shows very little desire to eat roughage when given a good- quality milk substitute diet ad lib. and that, even when the amounts of roughage consumed are small, this has a deleterious effect on carcass quality.