Bovine somatotropin increases the pregnancy rate in fixed‐time artificial insemination in beef cattle

This study evaluated the effect of bovine somatotropin (bST) on pregnancy rate (PR) and size of the dominant follicle (DF) on the day of intravaginal progesterone (P4) removal in protocols for fixed‐time artificial insemination (FTAI). Bos indicus (Nellore) females (n = 392) were distributed into three groups. The control group (CG; n = 92) received an intravaginal P4 device + estradiol benzoate on day (d)0; prostaglandin F2α on d7 (first application); removal of P4 + estradiol cypionate (EC) + PGF2α (second application) + ultrasound (US) of the DF on d9; the FTAI was performed on d11; and pregnancy diagnosis (PD) was performed on d45. The bST group (bSTG; n = 142) underwent the same protocol as the CG, except that the animals received 125 mg of bST on d7. The equine chorionic gonadotropin (eCG) group (eCGG; n = 158) underwent the same protocol as the CG, except that the animals received 300 IU of eCG on d9. The PRs of the bSTG, eCGG, and CG were 48%, 48%, and 35%, respectively (p