The nutrition of the veal calf. 3. A comparison of liquid skim milk with a diet of reconstituted spray-dried skim-milk powder containing 20 per cent margarine fat.

Abstract

1. Twenty-four bull calves consisting of fifteen Friesians and nine Ayrshires in a randomized block experiment were reared from birth on liquid diets offered ad lib. in two feeds daily to a slaughter weight equivalent to 22 % of mature cow weight of the breed.2. The three diets given after the calves had received 7 kg whole colostrum were (a) fresh liquid skim milk containing 0.1 % butterfat, (b) a ‘high-fat’ diet containing reconstituted spray-dried skim milk and 2.8 % margarine fat, and (c) the ‘high-fat’ diet for 14 d from birth followed by liquid skim milk. All calves received supplements of magnesium and iron, and vitamins A, D and E. Digestibility and balance trials were made on nine calves of each breed at both 4 and 10 weeks of age. Certain observations were made at slaughter.3. Dry-matter and gross energy intakes of calves given the skim-milk diet were greater than for those given the ‘ high-fat ’ diet. Daily weight gain, efficiency of food conversion, incidence of a high rectal temperature ( > 39.33°), mean rectal temperature and faecal dry-matter content were greater for the calves given the ‘ high-fat ’ diet. Age to slaughter and incidence of diarrhoea were much greater for the calves given liquid skim milk.4. Apparent digestibility of lactose and apparent absorption of ash and calcium were greater withthe ‘high-fat ’diet, but no difference occurred in apparent digestibility of dry matter or protein. Metabolic faecal fat excretion was estimated from the intercept of the relationship between apparently digested fat and fat intake for the calves given the liquid skim-milk diets; the values obtained ranged from 29 mg/kg live weight for Friesian calves at 10 weeks to 49.5 mg/kg for Ayrshire calves at 4 weeks. The true digestibility of the fat was estimated.5. No difference in Ca or nitrogen retention occurred between diets, but urinary N excretion and N retention/100 g gain in weight were markedly higher and concentration of N in the urine was much lower for calves given the skim milk.6. Perirenal fat deposition per unit of metabolic body size was 168 % greater for calves given the ‘ high-fat ’ diet. Kidney weight and skin weight were greater for the calves given the liquid skim-milk diet. The increased kidney weight was related to the very large urine output of the calves given skim milk.7. In comparison with Ayrshire calves, Friesian calves were much less susceptible to the adverse effects of liquid skim milk, having a lower incidence of diarrhoea and faeces of a higher dry-matter content, but they did have a higher incidence of lung lesions. Friesian calves also had a higher relative growth rate, efficiency of feed conversion, mean body temperature, faecal pH, apparent absorption of Ca, retention of N and Ca per unit of metabolic body size and killing-out percentage, but lower skin weight per unit of metabolic body size. Perirenal fat per unit of metabolic body size did not differ between breeds.