title: Effect of recombinant bovine somatotropin on estradiol-induced estrous behavior in ovariectomized heifers.
abstract: To evaluate whether bST administration could affect the intensity of estrous behavior in the absence of the ovary, 17 ovariectomized heifers were assigned to receive a placebo or 500 mg/14 d of recombinant bST and were induced to display behavioral estrus by administration of 2 mg of estradiol cypionate. Estrous behavior was monitored for the following 60 h with a surveillance camera and a video recorder, and mounting activity was quantified. Blood samples were collected before and after bST administration. Administration of bST numerically elevated plasma insulin and NEFA and caused a significant increase in concentration of insulin-like growth factor-I in plasma. Heifers that received bST started to display estrous behavior later (24.5 +/- 1.1 and 21.9 +/- 1.1 h after estradiol administration for bST and placebo treatments, respectively), displayed estrous behavior of shorter duration (bST, 13.2 +/- 1.2 vs. placebo, 15.8 +/- 1.1 h), and instigated fewer mounting events (bST, 45.5 +/- 5.9 vs. placebo, 62.6 +/- 5.7 mounts) than control heifers, although only the number of mounting events was significantly different between the two groups.
authors.affiliation: Department of Animal Science McGill University, Sainte-Anne de Bellevue, PQ, Canada.
authors.forename: D M
authors.initials: DM
authors.lastname: Lefebvre
authors.forename: E
authors.initials: E
authors.lastname: Block
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D010052:Ovariectomy / Q000662:veterinary; D011374:Progesterone / Q000097:blood; D011897:Random Allocation; D011994:Recombinant Proteins / Q000494:pharmacology; D014743:Videotape Recording
chemical_list: D005230:Fatty Acids, Nonesterified; D007328:Insulin; D011994:Recombinant Proteins; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone