An experiment was carried out with 20 male veal calves to study differences in energy metabolism between pure Dutch Friesian and Holstein Friesian crossbred calves, containing a high proportion of Holstein Friesian genes (0·79). Two metabolizable energy (ME) intakes were given. The effects of genotype and ME intake on live-weight gain and its fat and protein composition were measured by indirect calorimetry and by the total collection of faeces and urine. Energy and nitrogen balances were measured for each calf during the last 5 weeks of the fattening period of 22 weeks.
The difference in live-weight gain between the Holstein Friesian crossbreds and the Dutch Friesian calves was not significant but small differences in protein and fat composition of live-weight gain were found. Fat gain was closely related to ME intake (r = 0·95), but the correlation coefficient between ME intake and protein gain was only 0-36. Live-weight gain had a high correlation with protein gain (r = 0·70) but a lower correlation with fat gain (r = 0·29).
Veal calves at the end of the fattening period had a declining protein gain as age increased. Calves given a high ME intake (> 2 × maintenance) may require diets containing less than 216 g crude protein per kg diet at the end of the fattening period.
The study indicates that Holstein Friesian crossbred veal calves and Dutch Friesian veal calves have similar ME requirements.