1. Fifty-one Jersey, Ayrshire and British Friesian male calves were reared from birth to veal weights on one of three liquid diets.
2. Two ultra-high fat milk powders containing 680 g fat, either beef tallow (T) or a mixture of coconut oil and beef tallow (CT)/kg dry matter were prepared and mixed with liquid skim milk (35 g powder/kg) to give diets TLS and CTLS, containing 200 g fat/kg dry matter. A third diet consisted of reconstituted spray-dried skim milk powder containing 200 g margarine fat/kg (MDS).
3. The incidence of diarrhoea and of nasal discharge for all breeds, and of a high rectal temperature for the Ayrshire breed was greatest for calves given diet MDS and lowest for those given diet TLS. The incidence of lung lesions at slaughter was 100, 72 and 57% for the Jersey, Friesian and Ayrshire breeds respectively. Severity of lung lesions was lowest for calves given diet TLS.
4. Dry-matter intake and live-weight gain, especially for the Ayrshire breed, were greater for calves given diets containing liquid skim milk and the ultra-high fat powders (TLS and CTLS).
5. Fat digestibility was lowest on diet TLS. Protein digestibility increased with age. Digestibility of dry matter and lactose, and absorption of ash and calcium decreased with age. Calcium and N retention were lowest on diet MDS.
6. Killing-out percentage was highest for the Friesian and lowest for the Jersey breed. Perirenal fat deposition was highest for the Jersey and lowest for the Ayrshire breed. Skin weight/kg0·73 was higher for the Ayrshire calves than for the other two breeds.