Levantamento comparativo do desempenho reprodutivo de vacas com diferentes níveis de produção de leite

Abstract

This study aimed at correlating reproductive rates with milk production based on the evaluation of cows in different milk production levels in a commercial dairy herd located at Triângulo Mineiro region. A total of 241 cows of the following breeds were monitored: Holstein, Girolando, Jersey crossing with Holstein and Jersey in full stabling system, subjected to three daily milking and treated with recombinant bovine somatotropin (rbST) from the second month of lacta­tion until 60 days before the subsequent delivery. Conception rates, number of artificial inseminations (NAI), days between calving and first AI (FAI) and calving interval to conception (ICC) were estimated. Cows were grouped according to three independent criteria, average daily production (10-19; 20-29; 30-39; >40 kg day^-1), total production in lactation (<900; 1000-4999; 5000-9999; >10,000 L) and days in lactation (<150; 150-300; 300-450; 450-600 days). The results indicated that the days in lactation negatively influenced (P<0.001) the FAI, CIC and NAI. The number of inseminations was also influenced by total production during lactation. The maintenance of milk production through the use of rbST negatively influenced the reproductive rates.