title: Effect of human chorionic gonadotropin on luteal function and reproductive performance of high-producing lactating Holstein dairy cows.
abstract: The objectives were to evaluate effects of human chorionic gonadotropin (hCG) (3,300 IU i.m.) administered on d 5 after AI on CL number, plasma progesterone concentration, conception rate, and pregnancy loss in high-producing dairy cows. Following the synchronization of estrus and AI, 406 cows were injected with either hCG or saline on d 5 after AI in a randomized complete block design. Blood sampling and ovarian ultrasonography were conducted once between d 11 and 16 after AI. Pregnancy diagnoses were performed on d 28 by ultrasonography and on d 45 and 90 after AI by rectal palpation. Treatment with hCG on d 5 resulted in 86.2% of the cows with more than one CL compared with 23.2% in controls. Plasma progesterone concentrations were increased by 5.0 ng/mL in hCG-treated cows. The presence of more than one CL increased progesterone concentration in hCG-treated cows but not in controls. Conception rates were higher for hCG-treated cows on d 28 (45.8 > 38.7%), 45 (40.4 > 36.3%), and 90 (38.4 > 31.9%) after AI. Treatment with hCG improved conception rate in cows losing body condition between AI and d 28 after Al. Pregnancy losses were similar between treatment groups. Treatment with hCG on d 5 after AI induces accessory CL, enhances plasma progesterone concentration, and improves conception rate of high-producing dairy cows.
authors.affiliation: Veterinary Medicine Teaching and Research Center, University of California-Davis, Tulare 93274, USA. Jsantos@vmtrc.ucdavis.edu
authors.forename: J E
authors.initials: JE
authors.lastname: Santos
authors.forename: W W
authors.initials: WW
authors.lastname: Thatcher
authors.forename: L
authors.initials: L
authors.lastname: Pool
authors.forename: M W
authors.initials: MW
authors.lastname: Overton
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002417:Cattle / Q000502:physiology*; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D003338:Corpus Luteum / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005306:Fertilization / Q000187:drug effects*; D007273:Injections, Intramuscular / Q000662:veterinary; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation; D010053:Ovary / Q000000981:diagnostic imaging; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000097:blood*; D011897:Random Allocation; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D006063:Chorionic Gonadotropin; D011374:Progesterone