Effects of repeated embryo collection on embryo recovery rate in fertile mares

In mares, repeated embryo collection in successive oestrous cycles is necessary if a greater number of foals should be produced. We investigated effects of repeated embryo collection in fertile donor mares on embryo recovery rates. In addition, an influence of the individual mare and season on embryo recovery rates was studied. In nine mares, a total of 153 embryo collections were performed during 30 months (17 ± 2.2 embryo collections per mare). The overall embryo recovery rate was 64% and did not differ among mares. Between successive embryo collection procedures, recovery rate varied significantly; however, no increase or decrease in the embryo recovery rate with increasing number of successive embryo collections was seen. In three mares, ovulation ceased from November to February. In the remaining six mares, embryo production was successfully continued throughout winter and no influence of the month on embryo recovery rates was detected.