PREDICTABILITY OF EQUINE EMBRYO SIZE: Relation of embryo size to the interval between the application of the ovulation inducer and the uterine lavage

• Grant number: 22/16784-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2023
• End date: October 31, 2024
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Fernanda Saules Ignácio
• Grantee: Giovanna Nannini Sambi
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

The size of the equine embryo recovered in the programs of embryo transfer (ET) varies due to both the high initial growth rate of the embryo and the difficulty of monitoring the ovulation regularly in commercial programs of embryo transfer. Therefore, the objective of this study is to evaluate the possibility of predicting the size of the embryo recovered based on the time of ovulation induction. We will use 15 crossbred mares, in cyclic performance, with a good body condition and aged between 8 and 14 years old. The embryos recovered from these mares will be randomly divided into 4 groups: Group Des- 9.5 days - the embryo recovery will be performed on D8 (D0 = day of ovulation), between 230 and 234h from the ovulation induction; Group Des-10 days - the embryo recovery will be performed on D8, between 240 and 244h from the ovulation induction; Group Des- 10.5 days - the embryo recovery will be performed on D9, between 254 and 258h of the ovulation induction; Group Des- 11 days - embryo recovery will be performed on D9, between 264 and 268h of the ovulation induction. Times will be set for induction and uterine lavage so that the number of hours is standardized. The ovulation will be monitored every 12h from the ovulation induction with 1mg of intramuscular deslorrelin, and after 24h the AI will be performed (1x109 motile spermatozoa). The embryos will be evaluated and measured with a micrometer ruler. Analysis of variance will be conducted to determine the size of the embryo recovered among the different groups. Correlation will also be performed between the number of hours from ovulation induction to embryo collection and embryo size. Statistical differences will be determined with a significance level of 5% (P<0.05).