Effect of reproductive indices and bovine somatotropin on milk yield in Holstein cows experiencing climatic sub-fertility

Abstract

This study aimed at determining the association between reproductive indexes and the total milk yield in non-planed lactations ≥600 days in sub-fertile Holstein cows treated or not with recombinant bovine somatotropin (rbST) and experienced prolonged hyperthermia. A total of 1141 cows with a single lactation were enrolled in the study: 622 were not treated with rbST (control) and 519 were treated with rbST (500 mg every 14 days throughout lactation). Across parities, control cows with >480 days open, produced 5642 kg more milk (p380 days open and they continue to be inseminated after 10 unsuccessful services, the impact of delayed conception is not entirely negative as this disadvantage is more than outweighed by the extra milk that is produced when lactation is extended.

Keywords

• pregnancy rate
• heat stress
• days open
• lactation length
• services per conception