title: Effect of progesterone and/or estradiol treatments prior to induction of ovulation on subsequent luteal lifespan in anestrous Nelore cows.
abstract: Three experiments evaluated effects of estradiol (E(2)) and/or progesterone (P(4)) prior to induction of ovulation with GnRH on subsequent luteal lifespan in anestrous Nelore cows. In Experiment 1, cows (25-65 days post-partum [DPP]; n=114) were assigned randomly to receive a 6-day treatment with an intravaginal P(4) device (CIDR) and/or 1mg i.m. injection of 17beta-E(2) (4 groups; 2x2 factorial design) prior to ovulation. Blood samples were collected on days 0, 5, 7, 9, 12, 15 and 19 for evaluation of luteal function. Pre-treatment with P(4) reduced occurrence of premature luteolysis (PL; 79.2% in non-treated vs. 13.5% in treated cows; P<0.01), but there was no effect of treatment with 17beta-E(2) on percentage of PL. In Experiment 2, cows (30-40 DPP; n=35) were assigned randomly to receive either 0.5mL i.m. injection of cottonseed oil (placebo) or 1mg i.m. injection of E(2) cypionate. Blood samples were collected on days 0, 5, 9 and 15 for evaluation of luteal function. Incidence of PL (83.0% in Control Group vs. 75.0% in ECP Group; P>0.1) and mean serum P(4) did not differ between treatment groups. In Experiment 3, cows (30-60 DPP; n=109) were randomly assigned to receive either a 6-day (6-d Group) or a 3-day (3-d Group) treatment with CIDR. Blood samples were collected on days 0, 5, 7 and 9 for luteal function evaluation. Incidence of PL (5.5% in 6-day vs. 5.5% in 3-day groups; P>0.1) and mean serum P(4) did not differ between treatment groups. In conclusion, both 3- and 6-day treatments with P(4) prior to induction of ovulation in anestrous Nelore cows increased percentage of normal luteal lifespan, while administration of 1mg of 17beta-E(2) or E(2) cypionate failed to prevent occurrence of PL.
authors.affiliation: Departamento de Produção Animal, Faculdade de Medicina Veterinária e Zootecnia-UNESP, Botucatu-SP, Brazil.
authors.forename: Ocilon Gomes
authors.initials: OG
authors.lastname: Sá Filho
authors.forename: William Watters
authors.initials: WW
authors.lastname: Thatcher
authors.forename: José Luiz Moraes
authors.initials: JL
authors.lastname: Vasconcelos
mesh_terms: D000282:Administration, Intravaginal; D000780:Anestrus; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology*; D004958:Estradiol / Q000008:administration & dosage* / Q000031:analogs & derivatives; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007273:Injections, Intramuscular / Q000662:veterinary; D003341:Luteolysis / Q000187:drug effects; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D010919:Placebos; D011374:Progesterone / Q000008:administration & dosage* / Q000097:blood
chemical_list: D010919:Placebos; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; C007630:estradiol 17 beta-cypionate