Effects of daily gain in pre- and postpubertal replacement dairy heifers on body condition score, body size, metabolic profile, and future milk production

Two trials were conducted to evaluate the effect of moderate (0.7 kg) and a ccelerated (0.9 kg) average daily gain before (trial 1) and after (trial 2) puberty on body condition, metabolic profile, and first lactation milk pro duction of Italian Holstein-Friesian heifers. There were 20 heifers in tria l 1 and 22 in trial 2. Trials started when heifers averaged 150 and 300 kg of body weight in trial 1 and 2, respectively, and lasted 7 mo (experimenta l period). Across diet groups, half of the heifers were mated at first estr us after 370 kg and the other half after 420 kg of body weight gain. Actual average daily gains were 0.667 and 0.775 kg in trial 1 and 0.748 and 0.824 kg in trial 2 for moderate and accelerated experimental groups, respective ly. Diets for high average daily gain did not affect body condition during growing phase in trial 1, whereas it did in trial 2. High average daily gai n increased plasma glucose in trial 1 and plasma urea concentration in tria l 2. Rearing diet did not affect milk production and milk protein percentag e in both trials. High average daily gain decreased milk fat percentage in trial 2. Early calving negatively influenced milk production in both trials and milk fat percentage in trial 1. Early calving heifers showed higher pr otein percentage than those with late calving only in trial 1.