Chair of Advisory Committee: Dr. Clay A. Cavinder Studies performed on stallions have characterized detrimental effects on semen quality resulting from thermal stress by testicular insulation, but few have investigated the effects of exercise-induced increases in core body temperature on stallion semen parameters. To our knowledge, this is the first study that correlates subcutaneous scrotal temperature and stallion spermatozoa quality using a subdermal scrotal thermal sensory device. Stallions were assigned to a non-exercised (non-ex; control; n=4) or exercised (ex; n=4) group. A motorized equine exerciser was used to work stallions 30 min/d for 4 d/wk during a 12-wk period from July through October. Temperatures (subcutaneous scrotal, subcutaneous neck, rectal, and ambient) were recorded before exercise, immediately after exercise, and 60 and 120 min post-exercise. Humidity data were obtained later to determine THI.No deleterious effects were observed from implantation of thermal sensorydevices. An interaction of treatment and time (P < 0.0001) was evident for rectal and neck temperatures. The relationship between scrotal and rectal temperatures was highest (r s =0.761), and other correlations existed between scrotal, neck, and ambient iv temperatures, as well. Mean rectal temperature in the ex group increased 1.9°C (P < 0.0001), while there was a slight increase in scrotal temperature of 0.8°C (P > 0.05) from 0 min to 22 min. Although an increase in core body temperature was successfully induced by exercise protocol, scrotal temperatures were not significantly affected, and no treatment effects were found in any of the semen parameters measured (P > 0.05).Therefore, no significant changes in fresh or cooled semen parameters resulted from exercise or increases in core body temperature resulting from exercise protocol used in this study.Results of this study indicate that thermal sensory devices are a safe and effective way to measure subcutaneous scrotal and neck temperatures. Although an increase in core body temperature was successfully induced by exercise protocol, scrotal temperatures were not significantly affected, indicating efficient thermoregulation of the testes by the scrotum. Since the testes experienced no significant thermal insult during the exercise protocol, no significant changes in fresh or cooled semen parameters were evident as a result of exercise or elevated core temperature.v DEDICATION This thesis is dedicated to the two people I admire most, my parents. They forged the career path that I have chosen in life by providing me the opportunity to grow up with horses. Although this path has taken me far from home and family, I know that no matter the distances I travel, the unwavering love and support of my parents will always sustain me. Mom and Dad, I will forever be grateful for the sacrifices you have made to see me achieve my goals. Thank you; I love you; and I miss you every day.To my beloved horse and friend of only 5 short years: you will always be the horse to which I will compare ...

Stallions (n = 8) were implanted with a thermal sensory device in the muscle of the neck and the subcutaneous tissue of the scrotum and then assigned to either a nonexercise (Non-EX; n = 4) or exercise (EX; n = 4) group. A motorized equine exerciser was used to work EX stallions 30 min/d for 4 d/wk during a 12-wk period from July through October 2010. Temperatures (subcutaneous scrotal, intramuscular neck, and rectal) were recorded at 0, 22, and 30 min after the start of exercise, as well as 60 and 120 min post-exercise. Hourly ambient temperature and relative humidity data were also obtained. Semen was collected at 0, 4, 8, and 12 wk and analyzed for volume, sperm concentration, total sperm numbers, percentages of total and progressively motile sperm, sperm morphologic characteristics, and sperm DNA quality. No effect (P > 0.05) of exercise was observed on any of the measured semen variables. Implantation of thermal sensory devices had no demonstrable acute or chronic effects on the scrotal or neck tissue, indicating that the thermal sensory devices are a safe and effective way to measure subcutaneous scrotal and neck temperatures. At 22 and 30 min of exercise, rectal and neck temperatures increased (P < 0.0001) approximately 1.9 and 2.4°C, respectively, and scrotal temperatures simultaneously increased, although not significantly (P = 0.33), approximately 0.8°C. Correlations existed between scrotal, neck, rectal, and ambient temperatures, with the correlation between scrotal and rectal temperatures being greatest (r(s) = 0.76; P < 0.0001). Although moderate exercise for a short duration in extreme heat and humidity did significantly increase core body temperatures in stallions, scrotal temperatures did not significantly increase, and sperm parameters were unaffected.

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