| dc.description.abstract | Over the course of two breeding seasons, the ovarian activity and concentrations of progesterone, luteinizing hormone (LH), and cortisol were evaluated and compared in six exercising (EXER) mares and six non-exercising (NOEX) mares to illuminate any potential influence of exercise on ovarian and hormonal dynamics in mares. Blood samples were collected daily and the ovaries of all mares were evaluated daily by transrectal ultrasonography to track follicular activity and ovulation. No difference between the two groups was found in regard to interovulatory interval or the maximum size of the pre-ovulatory follicle. At d -5 relative to ovulation, EXER had more <10 mm, 10-15 mm, and 15.1-25 mm follicles on their ovaries. At d -1, there were more follicles present sized 15.1-25 mm and >25 mm in the NOEX group. In regard to basal cortisol concentrations, no difference was found between the EXER and NOEX groups when comparing levels at wk 3, 6, and 9 of the study. LH concentration was greater in the EXER mares on d -4, -3, 0, 1, 2, 3, and 4 relative to ovulation. When days were grouped by d -4 and -3, -2 and -1, 0, 1 and 2, and 3 and 4, EXER LH was higher at all periods. Progesterone concentrations were determined on d 9, 15, and 21 post-ovulation. There was no difference in progesterone concentration between the two groups at d 9, but progesterone was lower at d 15 in the EXER group. At d 21, several sample values from the exercised group appeared to be below the sensitivity of the assay. With the lowest assay sensitivity concentration entered in place of the missing data, the concentration of progesterone was found to be lower in the EXER mares when compared to their NOEX counterparts at d 21. Based on these findings, exercise-induced stress does exert an influence on the ovarian dynamics and the hormonal profiles of LH and progesterone in exercising mares at specific points during the estrous cycle. | en |
