125 Can endocrinology of the recipient mare predict the outcome of an in vitro-produced embryo transfer?
M. Papas A , J. Govaere A , S. Peere A , I. Gerits A , E. Van den Branden A , M. Van Eetvelde A , D. Angel-Velez B C , T. De Coster A , M. Hedia B D E and K. Smits AA Reproduction Biology Unit, Department of Internal Medicine, Reproduction and Population Medicine, Ghent University, Merelbeke, Belgium
B Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
C Research Group in Animal Sciences-INCA-CES, Universidad CES, Medellin, Colombia
D Theriogenology Department, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt
E Gamete Research Centre, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
Reproduction, Fertility and Development 35(2) 190-190 https://doi.org/10.1071/RDv35n2Ab125
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
In the past 10 years, significant advancements have been made in the production of in vitro embryos of sport horses through ovum pickup (OPU), intracytoplasmic sperm injection (ICSI), and embryo transfer (ET). Although many factors affect pregnancy rates, efficient selection of the recipient mare provides a keystone for the success of an OPU-ICSI-ET program. The aim of this study was to determine whether hormonal assessment could improve guidelines to select a suitable recipient mare in whom to transfer an in vitro-produced embryo. All mares were examined every day during oestrus until ovulation and were selected for an in vitro ET four days after their ovulation. In 66 different mares, a blood sample was taken at the time of the transfer to measure circulating progesterone (P4) and oestradiol (E2) concentrations, using an enzyme-linked fluorescent assay (miniVidas®, Biomérieux). Parameters such as tone of the cervix (grade 1: high tone; grade 2: moderate tone) and oedema of the endometrium (grade 1: no oedema; grade 2: some oedema) were evaluated via transrectal palpation and ultrasonography by four different specialists in equine reproduction and were recorded. Logistic regression models were built in R using the glmer() function with a binary responsive variable (pregnant or not pregnant). Operator was included in the model as a random factor. The percentage of mares pregnant 7 days after transfer was 45%. Mean concentrations (± s.d.) of progesterone and oestradiol were respectively 15.2 ± 6.65 ng/mL and 17.0 ± 10.45 pg/mL. While concentration of progesterone did not have any effect, higher oestradiol levels had a significant negative effect on pregnancy outcome (P = 0.025). An increase of 5 pg/mL in the oestradiol concentration was associated with 28% lower odds of becoming pregnant. A receiver operating characteristic (ROC) curve was used to determine the threshold for oestradiol above which a lower pregnancy rate can be expected. According to this ROC curve, the threshold was 27.9 pg/mL. Effect of P4/E2 ratio on pregnancy rate was not significant. Cervical tone and uterine oedema had a tendency to affect pregnancy outcome (respectively P = 0.081 and P = 0.077). In mares with a grade 2 of uterine oedema (n = 22), the odd ratio of becoming pregnant was only 0.36, compared with 1 in mares with grade 1. The odd ratio of pregnancy in mares presenting a grade 2 of cervical tone (n = 13) was only 0.27 compared with 1 in mares with a grade 1. In conclusion, rejection of recipient mares with oestradiol levels higher than 27.9 pg/mL Day 4 after ovulation may improve the results of an OPU-ICSI-ET program.
