Reproductive Differences in Cows Treated with rBST Compared to Cows Not Treated

Abstract

Numerous studies have reported decreased reproductive performance associated with administration of recombinant bovine somatotropin (rBST) to lactating dairy cows. However, most reports have been based on observations from studies conducted with small sample sizes or from target animal safety studies not designed to detect reproductive changes. This study was designed as a prospective clinical trial to provide more accurate measurement of reproductive changes associated with rBST use per label directions. The objectives of this study were to determine the effects of rBST on the survivability of the conceptus conceived within 24 days prior to the initiation of rBST, as well as effects on heat detection, conception and pregnancy rates after initiation of rBST treatment.