Date of Award

Winter 12-17-2016

Degree Type


Degree Name

Master of Science - Agriculture



First Advisor

Dr. John Michael Mehaffey

Second Advisor

Dr. Robin Parker

Third Advisor

Dr. Joey Bray

Fourth Advisor

Rachel Clark

Fifth Advisor

Dr. Stephanie Jones



Effect of Reproductive Efficiency in Regards to Workload on Peripheral Circulations of Blood Cortisol and Leptin in the Open Mare

(December, 2016)

Michaelle Kathleen Coker, B.S., Texas A&M University

Thesis Director: Dr. John Michael Mehaffey

Quarter and Paint horse mares (n= 9) were randomly assigned to 1 of 3 groups after being blocked based by expected conception date. Groups consist of mares on no work (NW), light work (LW), and moderate work (MW). Blood was taken weekly via jugular venipuncture prior to first heat cycle from each mare. Additionally, blood was taken at time of ovulation and then weekly until a 30 day (d) heartbeat was reported for the fetus. Each blood sample was assayed for leptin and cortisol concentrations, to see if cardiovascular fitness played a role in these reproductive hormones. There was a statistical difference between body weight (BW) (p-value < 0.0001) between the groups based on a week interaction. When blood leptin concentrations were observed for a successful 30d pregnancy between the groups, a statistical difference was seen between LW and MW (p-value < 0.0001). Statistical significance was seen between LW and NW (p-value = 0.0069) for serum cortisol levels for mares with successful 15d pregnancies. This study showed moderate workload could be beneficial on reproductive efficiency, while light work could be harmful to the open mare; however more research is needed.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.



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