Early calving heifers versus maiden heifers for beef production from dairy herds. I. The effects of genotype (Friesian and Charolais × Friesian) and two feeding levels in the rearing period on growth and carcass quality

Abstract

Three series of 64 heifers comprising two genotypes (Friesian and Charolais × Friesian) and two feeding levels between 5 and 14 months of age (high:H and moderate:M) were compared. Two-thirds of the heifers were mated at 10 months of age, the others remaining maiden. Liveweight gains between 5 and 14 months were 900 g day −1 for H level and 700 g day −1 for M level, with a better feed efficiency for Charolais × Friesian. One hundred and fifty-eight heifers were slaughtered at an average of 23.5 months of age with hot carcass weights of 265 kg; the crossbred heifers had higher liveweights and heavier carcasses with a better dressing percentage and less fat than Friesian heifers. Calved heifers were slaughtered later than the maidens and had lighter carcasses (equal at 4 weeks more). The average age at the first A.I. was 311 days, with an average liveweight of 266 kg for Friesians and 283 kg for crossbred heifers. Calving rate was higher for Friesians (92% against 77% for crossbreds) and for H level (91% against 78% for M level). The low level of calving difficulties was probably due to the small size of the calves at birth (32 kg) in relation to the sire genotype (Aubrac and Aberdeen-Angus). The early calving at 20 months only slightly affected the muscle development in Friesian and Charolais × Friesian heifers slaughtered at 2 years of age. The Charolais crossbreeding significantly improved meat production. This production system represents a possible increase of beef production potential from female calves born in dairy herds. However, the economic benefits are poor under French beef marketing conditions.