High numbers of antral follicles are positively associated with in vitro embryo production but not the conception rate for FTAI in Nelore cattle

• Published in: Animal reproduction science 2016-02, Vol.165, p.17-21
• Main Authors: Santos, Gustavo Martins Gomes dos, Silva-Santos, Katia Cristina, Barreiros, Thales Ricardo Rigo, Morotti, Fábio, Sanches, Bruno Valente, de Moraes, Fábio Lucas Zito, Blaschi, Wanessa, Seneda, Marcelo Marcondes
• Format: Article
• Language: English
• Subjects: Animals; Antral follicles; Cattle; Cattle - physiology; Conception rate; Embryo Culture Techniques - veterinary; Embryos; Female; Fertilization - physiology; Oocytes; Ovarian Follicle - physiology; Tissue and Organ Harvesting - veterinary
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2015.11.024

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 (2×108/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