title: High numbers of antral follicles are positively associated with in vitro embryo production but not the conception rate for FTAI in Nelore cattle.
abstract: The objective was to compare the conception rates for FTAI and in vitro embryo production between Nelore cows with different antral follicle counts (AFC=number of follicles ≤3mm in diameter in the ovaries). Nelore cows (n=547) were subjected to ovulation synchronization. Randomly during the estrous cycle (D0), cows received an intravaginal device containing 1.9g P4 (CIDR(®)) and 2mg BE (Estrogin(®)), IM. When the device was removed (D8), the cows received 500μg PGF2α (Ciosin(®)), 300IU eCG (Novormon(®)) and 1mg EC (ECP(®)), IM. All cows were inseminated 48h after P4 device removal. Antral follicles ≥3mm were counted using an intravaginal microconvex transducer (D0), and the cows were assigned to high (G-High, ≥25 follicles, n=183), intermediate (G-Intermediate, 16-20 follicles, n=183) or low AFC groups (G-Low, ≤10 follicles, n=181). In another experiment, COCs were retrieved by OPU from Nelore cows (n=66), which were assigned to groups according to oocyte production: G-High (n=22, ≥40 oocytes), G-Intermediate (n=25, 18-25 oocytes) or G-Low (n=19, ≤7 oocytes). All COCs from the same cow were cultured individually (maximum of 25 COCs per drop) and then in vitro fertilized using thawed frozen sperm (2×10(8)/dose) from a Nelore sire of known fertility. The data were analyzed using a Kruskal-Wallis and a Chi-square test (P≤0.05). There was no difference in the conception rates after FTAI between Nelore cows with high, intermediate or low AFC (51.9 vs. 48.6 vs. 58.6%). The number of viable embryos was 18.4±6.7 (G-High), 6.1±3.6 (G-Intermediate) and 0.6±0.7 (G-Low; P<0.05). Therefore, AFC had no influence on the conception rates for FTAI; however, Nelore cows with high oocyte production exhibited better in vitro embryo production.
authors.affiliation: Laboratório de Biotecnologia da Reprodução Animal (ReproA), DCV-CCA-Universidade Estadual de Londrina (UEL), Londrina 86051-990, PR, Brazil.
authors.forename: Gustavo Martins Gomes Dos
authors.initials: GMGD
authors.lastname: Santos
authors.affiliation: Laboratório de Biotecnologia da Reprodução Animal (ReproA), DCV-CCA-Universidade Estadual de Londrina (UEL), Londrina 86051-990, PR, Brazil.
authors.forename: Katia Cristina
authors.initials: KC
authors.lastname: Silva-Santos
authors.affiliation: Laboratório de Reprodução Animal, Universidade Estadual do Norte do Paraná (Uenp), Bandeirantes 86360-000, PR, Brazil.
authors.forename: Thales Ricardo Rigo
authors.initials: TRR
authors.lastname: Barreiros
authors.affiliation: Laboratório de Biotecnologia da Reprodução Animal (ReproA), DCV-CCA-Universidade Estadual de Londrina (UEL), Londrina 86051-990, PR, Brazil.
authors.forename: Fábio
authors.initials: F
authors.lastname: Morotti
authors.affiliation: Laboratório de Biotecnologia da Reprodução Animal (ReproA), DCV-CCA-Universidade Estadual de Londrina (UEL), Londrina 86051-990, PR, Brazil.
authors.forename: Bruno Valente
authors.initials: BV
authors.lastname: Sanches
authors.affiliation: Laboratório de Biotecnologia da Reprodução Animal (ReproA), DCV-CCA-Universidade Estadual de Londrina (UEL), Londrina 86051-990, PR, Brazil.
authors.forename: Fábio Lucas Zito
authors.initials: FLZ
authors.lastname: de Moraes
authors.affiliation: Laboratório de Reprodução Animal, Universidade Estadual do Norte do Paraná (Uenp), Bandeirantes 86360-000, PR, Brazil.
authors.forename: Wanessa
authors.initials: W
authors.lastname: Blaschi
authors.affiliation: Laboratório de Biotecnologia da Reprodução Animal (ReproA), DCV-CCA-Universidade Estadual de Londrina (UEL), Londrina 86051-990, PR, Brazil. Electronic address: mseneda@uel.br.
authors.forename: Marcelo Marcondes
authors.initials: MM
authors.lastname: Seneda
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D046149:Embryo Culture Techniques / Q000662:veterinary*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D006080:Ovarian Follicle / Q000502:physiology*; D020858:Tissue and Organ Harvesting / Q000662:veterinary
keywords: Antral follicles; Cattle; Conception rate; Embryos; Oocytes