Endocrine and ovarian response to therapy with PROGESTERONE-RELEASING intravaginal device associated with estradiol benzoate in mares

• Grant number: 13/17669-0
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: March 01, 2014
• End date: February 28, 2015
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Cezinande de Meira
• Grantee: Jair Camargo Ferreira
• Supervisor: Donald Thompson
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil
• Institution abroad: Louisiana State University (LSU), United States
• Associated to the scholarship: 12/01627-4 - Temporal relationship between angiogenic factors, luteal hemodynamics and plasma hormonal concentrations during the luteolysis (total and partial) and throughout the post-luteolytic and CL resurging phases in mares, BP.PD

Abstract

Progesterone-releasing devices associated with steroids, PGF and hCG have been successfully used to control estrus and ovulation in cows, while progestin therapies have been performed to extend the luteal phase in mares. However, intravaginal progesterone (P4) protocols for estrus synchronization in mares have resulted in unsatisfactory results at this moment. The characterization of plasmatic concentration of LH and P4 of mares treated with progesterone-releasing intravaginal devices, associated or not with estradiol benzoate, will be essential for the establishment of new approaches aiming to improve estrus synchronization protocols. A total of 56 mares will be used to evaluate the influence of progestin therapy on follicular development during distinct stages of the estrus cycle. Follicles >6mm of all mares will be aspirated. Posteriorly, the mares will be assigned into seven experimental groups (n=8 mares/group) according to hormonal protocol and moment of treatment. Two hormonal protocols will be used: Progestin-releasing device alone or associated with 10 mL of benzoate estradiol. Progestin devices will be kept intravaginally for 10 days. Treatments will be performed in one of three distinct phases of the estrus cycle according to the largest follicle diameter post-ablation (>6mm, >20mm or >35mm). Additionally, a group of non-treated mares will be used as a control group. Blood samples will be collected every day from D0 to D10 (D0=day of device insertion) to measure plasma LH and P4 concentration. Ultrasound exam will be performed every 24 hours from the day of follicular ablation procedure until the next ovulation to determine follicular growth rate and day of ovulation (AU)