Period of dominance of the ovulatory follicle on embryo quality in Bos indicus and Bos taurus cattle

• Grant number: 19/15129-5
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Effective date (Start): October 14, 2019
• Effective date (End): March 23, 2020
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Roberto Sartori Filho
• Grantee: Rodrigo Lemos Olivieri Rodrigues Alves
• Supervisor: Ky G. Pohler
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Research place: Texas A&M University, United States
• Associated to the scholarship: 18/14723-8 - Influence of duration of follicle dominance on embryo quality and fertility of Nelore cows, BP.MS

Abstract

Follicular growth during bovine estrous cycle occurs in the form of waves and consists of the following phases: 1) emergence of the follicular wave (FW), in which the follicles present 4 mm in diameter; 2) follicular deviation (FD), that occurs when follicles are measuring around 8.5 mm diameter in Bos taurus and 6 to 7 mm in Bos indicus and 3) ovulation, in which the developing dominant follicle responds to a pre-ovulatory luteinizing hormone (LH) surge. Studies performed in dairy and beef Bos taurus heifers and cows reported a negative effect of the length of follicle dominance on oocyte quality, embryo development and fertility. However, preliminary data from our lab from a recent study suggested little or even no effect of follicle persistence on fertility of Bos indicus (Nelore) cows, although more studies are necessary. Therefore, in order to investigate if different genetic groups have distinct oocyte sensitivity to development of persistent follicles, the present study aims to evaluate the impact of follicle age (period of dominance) on embryo quality of Bos indicus (Brahman) vs. Bos taurus (Aberdeen Angus) cattle or heifers. Thus, 80 cows or heifers (40 from each genetic group) will be submitted to a presynchronization protocol followed by a treatment developed to generate persistent follicles. At the end of the protocol, cows will be submitted to fixed time artificial insemination (FTAI). Seven days after AI, non-surgical transcervical uterine flushing will be performed for embryo recovery and evaluation. The main hypothesis is that the extended follicular dominance negatively affects embryo quality in Bos taurus but not in Bos indicus. (AU)