title: The effect of type of vaginal insert and dose of pLH on embryo production, following fixed-time AI in a progestin-based superstimulatory protocol in Nelore cattle.
abstract: The objective was to analyze and report field data focusing on the effect of type of progesterone-releasing vaginal insert and dose of pLH on embryo production, following a superstimulatory protocol involving fixed-time artificial insemination (FTAI) in Nelore cattle (Bos taurus indicus). Donor heifers and cows (n = 68; 136 superstimulations over 2 years) received an intravaginal, progesterone-releasing insert (CIDR or DIB, with 1.9 or 1.0 g progesterone, respectively) and 3-4 mg of estradiol benzoate (EB) i.m. at random stages of the estrous cycle. Five days later (designated Day 0), cattle were superstimulated with a total of 120-200 mg of pFSH (Folltropin-V), given twice daily in decreasing doses from Days 0 to 3. All cattle received two luteolytic doses of PGF2alpha at 08:00 and 20:00 h on Day 2 and progesterone inserts were removed at 20:00 h on Day 3 (36 h after the first PGF2alpha injection). Ovulation was induced with pLH (Lutropin-V, 12.5 or 25 mg, i.m.) at 08:00 h on Day 4 with FTAI 12, 24 and in several cases, 36 h later. Embryos were recovered on Days 11 or 12, graded and transferred to synchronous recipients. Overall, the mean (+/-S.E.M.) number of total ova/embryos (13.3 +/- 0.8) and viable embryos (9.4 +/- 0.6) and pregnancy rate (43.5%; 528/1213) did not differ among groups, but embryo viability rate (overall, 70.8%) was higher in donors with a DIB (72.3%) than a CIDR (68.3%, P = 0.007). In conclusion, the administration of pLH 12 h after progesterone removal in a progestin-based superstimulatory protocol facilitated fixed-time AI in Nelore donors, with embryo production, embryo viability and pregnancy rates after embryo transfer, comparable to published results where estrus detection and AI was done. Results suggested a possible alternative, which would eliminate the need for estrus detection in donors.
authors.affiliation: Department of Pharmacology, Institute of Biosciences, University of São Paulo State (UNESP), Distrito de Rubiao Jr. s/n, 18618000, Botucatu, São Paulo, Brazil.
authors.forename: Marcelo F Gouveia
authors.initials: MF
authors.lastname: Nogueira
authors.forename: Paulo S
authors.initials: PS
authors.lastname: Fragnito
authors.forename: Luzia A
authors.initials: LA
authors.lastname: Trinca
authors.forename: Ciro M
authors.initials: CM
authors.lastname: Barros
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004622:Embryo, Mammalian / Q000502:physiology; D005260:Female; D006728:Hormones / Q000008:administration & dosage / Q000494:pharmacology; D007315:Insemination, Artificial / Q000662:veterinary*; D007986:Luteinizing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D011247:Pregnancy; D018873:Pregnancy Rate; D011372:Progestins / Q000008:administration & dosage*; D012098:Reproduction / Q000187:drug effects*
chemical_list: D006728:Hormones; D011372:Progestins; D007986:Luteinizing Hormone