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Ovarian characteristics and oocyte quality of aged Nelore cows

Grant number: 18/07450-5
Support type:Regular Research Grants
Duration: March 01, 2019 - February 28, 2021
Field of knowledge:Agronomical Sciences - Veterinary Medicine
Principal Investigator:Rafael Herrera Alvarez
Grantee:Rafael Herrera Alvarez
Home Institution: Departamento de Descentralização do Desenvolvimento (APTA Regional). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Campinas , SP, Brazil
Assoc. researchers:Fabiana Ferreira de Souza ; Guilherme Pugliesi ; Keila Maria Roncato Duarte ; Yeda Fumie Watanabe
Associated scholarship(s):19/05682-9 - Ovarian characteristics and oocyte quality of aged Nellore cows, BP.TT

Abstract

In the bovine species, information on how biological ageing affects reproductive physiology and the quality of gametes is sparse and limited. The main obstacle to carrying out studies on the influence of age on the reproduction of cattle derives from the difficulty of finding adequate experimental material, since commercial farms discard their animals long before they cease their reproductive capacity. The objective of this project is to characterize the ovarian function, oocyte quality, as well as to identify specific biomarkers associated to fertility or longevivity in Nellore cows. We intend to answer the following hypotheses: 1) the ovarian dynamics (follicular waves) independ of the age of the cows, but can be affected by the follicular population; 2) plasmatic hormone concentrations (particularly AMH) are different in young and aged cows. The decline in AMH would be related to the total number of antral follicles in the ovaries; 3) the hormonal and protein composition of the follicular fluid of aged cows with good fertility would be different from that found in low-fertility young cows; 4) oocytes of aged cows had lower quality compared with oocytes of young cows, and the addition of antioxidant substances to the culture medium would be able to reverse the poor quality these oocytes. Specific experiments using aged and young cows with good fertility and young cows with compromised fertility (cows failed to be pregnant when inseminated or exposed to the bull for more than 4 months) were designed to respond to these assertions. The evaluation of ovarian dynamics will be performed using non-invasive techniques (Doppler ultrasound); hormonal dosages will be performed using RIA and ELISA techniques; the determination of proteins in the LF will be performed using associated techniques of HPLC-MS PAGE; oocyte retrieval will be performed in vivo by OPU, and the embryonic development by using conventional in vitro culture techniques. In conclusion, the project is expected to contribute to the advancement in the knowledge of the reproductive physiology of aged cows, to identify biomarkers related to longevity and to improve the rate of embryonic development resulting from the supplementation in the culture medium of substances with antioxidant activity. (AU)