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1 Azienda Sperimentale "V. Tadini", 29027 Gariga di Podenzano (PC), Italy
2 Istituto di Zootecnica, Facoltà di Agraria, Università Cattolica Sacro Cuore, 29100 Piacenza, Italy
3 Istituto Sperimentale per la Zootecnia, 26100 Cremona, Italy
Two trials were conducted to evaluate the effect of moderate (0.7 kg) and accelerated (0.9 kg) average daily gain before (trial 1) and after (trial 2) puberty on body condition, metabolic profile, and first lactation milk production of Italian Holstein-Friesian heifers. There were 20 heifers in trial 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 (experimental period). Across diet groups, half of the heifers were mated at first estrus 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, respectively. 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 gain increased plasma glucose in trial 1 and plasma urea concentration in trial 2. Rearing diet did not affect milk production and milk protein percentage 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 protein percentage than those with late calving only in trial 1.
Key Words: dairy heifer growth metabolic profile first lactation
Submitted on October 8, 1999
Accepted on February 2, 2000
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