Repeated embryo recovery attempts and subsequent fertility of two-year-old fillies
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abstract
The objectives of this study were to determine if 2-year-old fillies could be used successfully for embryo donors and whether repeated embryo recovery attempts would affect subsequent fertility. Twenty-three (Year 1) and 16 (Year 2) 2-year-old fillies were evaluated as embryo donors. The fillies were teased and palpated daily. When a follicle was palpated, the fillies were inseminated (500 106 motile spermatozoa) every other day until ovulation was detected. Nonsurgical embryo recoveries were attempted on Days 5 and 6 (-120 and 144 hours) postovulation for a total of 32 times for 16 fillies (Year 1). No embryos were recovered on Day 5. However, seven embryos were recovered during the subsequent collection on Day 6. Fifty-one additional embryos and 19 degenerated ova were recovered from 120 collection attempts which were performed only on Day 6 (Year 1). Eighteen embryos and eight degenerated ova were recovered from 38 collection attempts on Day 6 in Year 2. Mean collections per filly were 8 (range 3 to 16) and 2.69 (range 1 to 4) for Years 1 and 2, respectively. No differences (P>0.05) were found in the interval from collection (prostaglandin injection) to the first day of estrus or from the first day of estrus to ovulation for the collection periods during either year. Moreover, no differences (P>0.05) were found in the interval between collections within or between years. The influence of repeated embryo recovery on subsequent fertility was studied using eight fillies which had undergone collections a mean of 12 times in Year 1. Five of the eight fillies conceived during the first estrous cycle and the remaining three conceived during the second cycle. All fillies produced normal healthy foals and were rebred on the first or second estrous cycle postpartum. These results indicate that repeated embryo recovery attempts yield multiple embryos and do not compromise the subsequent reproductive performance of 2-year-old fillies. 1991.
