title: Effect of a single growth hormone (rbST) treatment at breeding on conception rates and pregnancy retention in dairy and beef cattle.
abstract: Initiation of long-term treatment with rbST (Posilac, Monsanto, St. Louis, MO) coincident with first insemination increased pregnancy rates in dairy cattle, but neither the efficacy of using only the initial injection, nor its effects on retention of pregnancy are known. Lactating dairy cows, dairy heifers, and lactating beef cows were assigned at random to treatment (rbST) or control. Dairy cows, dairy heifers, and beef cows received 500 mg rbST (n = 48, 35, 137 inseminations, respectively) at artificial insemination or were left untreated (n = 62, 33, 130 inseminations, respectively). Pregnancy was diagnosed by ultrasonography at 28-36 days. Treatment with rbST at insemination improved conception rates in dairy cows (60.4% versus 40.3%; P < 0.05), but not in dairy heifers or beef cows. Conception rates did not differ in dairy cows at < or =100 days in milk (DIM), but were improved in cows treated with rbST after 100 DIM (64.3% versus 25.8%; P < 0.05). Retention of pregnancy to approximately 60 days and sizes of CL, diameter of follicles > or =5 mm, and crown-rump lengths of embryos were not affected by treatment. The second objective was to examine the effects of rbST at insemination on birth weight and post-natal calf growth in beef cows. However, birth and weaning weights of beef calves were not affected by treatment. In conclusion, a single treatment with rbST at insemination increased conception rates in dairy cows, specifically in those >100 DIM.
authors.affiliation: Division of Animal and Veterinary Science, West Virginia University, G040 Agricultural Sciences, P.O. Box 6108, Morgantown, WV 26506-6108, USA.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Starbuck
authors.forename: E Keith
authors.initials: EK
authors.lastname: Inskeep
authors.forename: Robert A
authors.initials: RA
authors.lastname: Dailey
mesh_terms: D000375:Aging; D000818:Animals; D001823:Body Composition; D001947:Breeding / Q000379:methods*; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D018568:Crown-Rump Length; D004958:Estradiol / Q000097:blood; D005260:Female; D005306:Fertilization / Q000187:drug effects*; D005865:Gestational Age; D013006:Growth Hormone / Q000008:administration & dosage*; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation; D006080:Ovarian Follicle / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D011994:Recombinant Proteins; D014463:Ultrasonography
chemical_list: D011994:Recombinant Proteins; C073294:growth hormone, bovine; D011374:Progesterone; D004958:Estradiol; D013006:Growth Hormone