Date of Award

5-2010

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Animal Physiology

Advisor

Vernon, Kristine L

Committee Member

Mortensen , Christopher J

Committee Member

Bodine , Ashby B

Abstract

Athletic mares are commonly utilized in an embryo transfer regimen during the breeding season, which allows owners to continue to train and compete with these animals. Evidence suggests exercising mares in a hot and humid environment detrimental to embryo recovery rates. However, the effects of exercise under milder temperatures and its influence on mare reproduction have not been thoroughly examined. Our goal was to compare embryo recovery rates and embryo quality scores of mares under mild environmental conditions of two differing exercise regimens versus a single Control group. Color Doppler ultrasonography was used to capture images of the blood flow surrounding the dominant follicle one day prior to ovulation to assess the importance of blood flow to the dominant follicle and subsequent embryo quality. The Full-Exercise group consisted of mares (n = 6) exercised 6 d a week throughout the duration of the project. The Partial-Exercise group (n = 6) was exercised throughout the project 7 d a week, with full rest from day of detected ovulation to attempted embryo collection. The purpose of the resting period was to limit any deleterious effects exercise may potentially have on the mare and subsequent early developing embryo. Exercise, in the Partial-Exercise group, resumed the day after an attempted embryo collection. Mean environmental temperature during this study was 27.1°C and average humidity of 60%. Immediately following completion of exercise, both groups of exercise mares had a mean increase in rectal temperatures of 1.0°C (±0.094; P=0.0001) and after 30-min recovery period a decline of 0.5°C (±0.084; P=0.0001). Cortisol concentrations were increased in exercise groups compared to non-exercised Control mares (P=0.027) and acclimation to stress was seen in the Full-Exercise group when cortisol concentrations decreased over the study (P=0.020). Exercise had a significant effect on embryo quality (Control 1.07 ±0.27, partial 2.14±0.27, full 1.50±0.34) (P=0.028); however, did not influence embryo recovery rate. The percentage of blood perfusion surrounding the preovulatory follicle was higher in all groups when an embryo was retrieved (mean 53.98±2.76%) compared to an unsuccessful uterine flush (mean 41.17±3.09%; P=0.0218). The percentage of blood perfusion tended to be different between groups (non-exercise Control 54.9±3.55%, Partial-Exercise 46.9±3.04%, Full-Exercise 43.6±3.39%; P=0.077). It appears from these data, that exercise has a negative effect on embryo quality, thus lowering the availability of transferable embryos. Additionally, the introduction of a resting period from ovulation to embryo collection attempt did not improve embryo quality.

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