Plasma concentrations of estrogen and progesterone in non-cyclic mares treated with estradiol and long-action progesterone

• Grant number: 14/15375-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2014
• End date: September 30, 2015
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Cezinande de Meira
• Grantee: Anny Raissa Carolini Gomes
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Estrogens and progestins treatments are usually applied to prepare non-cyclic recipient mares for embryo transfer programs. Although standardized protocols for exogenous progestins are already described, there are no studies determining the dose and administration frequency of benzoate estradiol, followed by progestins administration, that produce similar hormone profile to that found in cyclic mares. The present study aims to evaluate the influence of different doses and administration frequencies of estradiol benzoate followed by long action progesterone administration on estrogen and progesterone plasma concentrations in non-cyclic embryo recipient mares. Twenty one anestrous mares will be distributed into the following groups (n=7 mares/group): G1, in which decreasing doses of 10 mg of estradiol benzoate (EB) on three consecutive days (5, 3 and 2 mg) followed by 1500 mg of long action progesterone (LA P4) will be given; and G2, in which decreasing doses of 5 mg of EB on two consecutive days (3 and 2 mg) followed by 1500 mg of LA P4 will be administered. These mares will be reevaluated during the ovulatory phase and seven of them will be part of the non-treated Control group. During the hormonal treatments in non-cyclic mares and corresponding cyclic phase (estrous and early diestrous) in the Control group, B-mode ultrasonography will be performed and daily blood samples will be collected to measure estradiol and progesterone. The knowledge of an estrogen followed by progestin protocol that is more compatible with endogenous concentrations found in cyclic mares will allow an optimization of the use of these hormones in non-cyclic embryo recipient mares.