Effects of winter feeding during the rearing period on performance and longevity in dairy cattle

Abstract Black and White dairy heifers born in autumn and programmed for early calving at approximately 2 years of age were given HIGH (H) or LOW (L) feeding treatments during each wintering period of the rearing stage according to a factorial arrangement: from birth to 6 months (H1 or L1) and between 12–18 months (H2 or L2). H1 and H2 treatments increased energetic supplies by 22 (100 UFL) and 49 (400 UFL) per cent. HIGH feeding treatments resulted in higher winter gains (H1:826 g/d, L1:696 g/d, H2:885 g/d, L2:639 g/d). During summer grazings, compensatory growth was moderate (50 to 55%). Feeding treatments had no effects on milk yield for each lactation. However H1 treatment contributed to a longer productive life (+333 days) along with higher milk (+4089 kg), fat (+205 kg) and protein (+150 kg) yields. H1 cows produced more calves (+0.9) and heavier carcasses at culling (+20 kg). H2 heifers needed less veterinary assistance at first calving. Mastitis troubles were less frequent and mortality was lower in H1. Hence, the live-weight of 6 month-old heifers should amount to 30% of adult cow weight. The ideal weights are judged to be 60% and 90% of mature cow weight at AI (at age 15 months) and before the first calving (at 24 months).