Effect of the interval from Prostaglandin F2α treatment to ovulation on Embryo Recovery Rate and subsequent Pregnancy Rate in a commercial Equine Embryo Transfer program

PIETRANI, M.S.; CUERVO ARANGO, J.; LOSINNO, L.

JOURNAL OF EQUINE VETERINARY SCIENCE

ELSEVIER SCIENCE INC

Año: 2016 vol. 41

0737-0806

Prostaglandin F2α and its synthetic analogues (PGF) are routinely used in equine embryo transfer (ET) programs in order to obtain the largest number of cycles/embryos per mare during the breeding season. The Interval from PGF treatment to ovulation (ITO) varies widely in the mare, from 2 to 16 days [1]. The main factors affecting ITO are the diameter of the largest follicle at the time of treatment and whether it is destined to ovulate or regress. Ovulation can occur in a very short period of time (i.e. 28 mm in diameter). It has been suggested that fertility of these cycles is lower [2-4]. The objective of this retrospective study was to evaluate the effect of ITO on the Embryo Recovery Rates (ERR) and the effect of ITO after which embryo was recovered on Pregnancy Rates (PR) in recipient mares. Data were obtained from a retrospective analysis over 2.568 cycles of 180 Polo Argentino donor mares from an ET program in Argentina. Mares were inseminated with fresh semen from 31 fertile stallions. Embryo flushing was performed 7 to 8 days post-ovulation. Following embryo flushing, donor mares were treated with PGF (cloprostenol 250 µg, Estrumate, Intervet). For statistical analyses purposes, ITO data were classified in one-day groups from 4 to 12 days, while ITO from 1 to 3 and ITO ≥13 days were pooled in one group. Data were analyzed by a logistic binary regression model to determine the effect of the ITO on ERR. Chi-square test was used to test the difference in ERR amongst ITO groups and the effect of ITO on PR.The ITO had a significant effect on ERR (P=0.01). The highest ERR were found in mares with ITO between 6 to 10 days. The ERR of mares with ITO of ≥11 days were numerically lower but not statistically different from those of mares with ITO of 6 to 10 days. The lowest ERR were found in mares with ITO