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Embryo recovery from exercised mares
- Mortensen, C.J., Choi, Y.H., Hinrichs, K., Ing, N.H., Kraemer, D.C., Vogelsang, S.G., Vogelsang, M.M.
- Animal reproduction science 2009 v.110 no.3-4 pp. 237-244
- mares, embryo transfer, female fertility, reproductive efficiency, exercise, ambient temperature, relative humidity, heat stress, physiological response, estrous cycle, follicular development, ovulation, conception, embryogenesis, embryo (animal), viability
- The effect of exercise on mare reproductive efficiency was evaluated by comparing rates of embryo recovery from mares assigned to either an exercise regimen or a non-exercise (control) regimen. Exercised mares were worked daily for 30min under average ambient conditions of >30°C and >50% humidity. Mares were inseminated during estrus and subjected to uterine flush for embryo recovery on d 7 after ovulation for two consecutive cycles. After this, mares were allocated to the opposite group and allowed an estrous cycle without reproductive manipulation; then insemination and uterine flushing were conducted on two more consecutive cycles. Prostaglandin F₂α was administered on the day of uterine flush. Mare rectal temperature increased during exercise from a mean of 38°C to a mean of 39.9°C. Mares had ovulations from smaller follicles when exercised than they did under control conditions (39.8±0.5 compared with 41.5±0.5mm diameter; P <0.05), and had an increased time from PGF₂α administration to subsequent ovulation (8.47±0.337 compared with 9.27±0.294 d; P <0.05). Embryo recovery from control mares was 22 of 35 (63%). Fewer embryos were recovered from exercised mares (11 of 32, 34%; P <0.05). The proportion of embryos classified as Grade 1 tended to be less in exercised than in non-exercised mares (4 of 11, 36% compared with 16 of 22, 73%; P =0.051). These data indicate that exercising mares in a hot and humid environment are associated with changes in ovarian follicle development and ovulation, and a reduction in embryo recovery.