Date of Award


Document Type


Degree Name

Master of Science (MS)

Legacy Department

Animal Physiology

Committee Chair/Advisor

Vernon, Kristine

Committee Member

Mortensen , Christopher

Committee Member

Birrenkott , Glenn


Horses are natural athletes and are commonly competed during early pregnancy. Because horses have singleton pregnancies and are conditioned to human interaction, they may prove to be a useful model in lending greater understanding of the numerous etiologies of intra-uterine growth restriction that is found in women and other mammals. Currently, there has been little research conducted to determine the effects that stress, in the form of aerobic exercise, has on early embryonic and fetal development in the horse. More research is needed to further understand the effects that stress has on early conceptus development in the mare.
The research trial consisted of eight light breed mares that were randomly designated to a non-exercise control group and an exercise treatment group. The treatment mares were exercised from Days 16 to 80 of pregnancy. Color Doppler ultrasound was utilized in all mares to evaluate embryonic vesicle size, embryo proper growth, fetal crown-to-rump length, and uterine blood flow of both the gravid and non-gravid uterine arteries. Jugular venipuncture was performed in both groups to identify the serum cortisol and progesterone concentrations between Days 16 to 80 of gestation. Exercise treatment, ultrasonography, and blood draws ended on Day 80 of pregnancy.
Results of this study indicated that exercise treatment lead to a larger embryonic vesicle in the treatment group (P=0.005) than the control group, but the embryo proper and fetal crown-to-rump length were similar between groups. Uterine artery blood flow velocity was significantly greater in the gravid and non-gravid horns of the exercise mares (P=0.001; P<0.001) than the control mares. Cortisol concentrations were significantly higher in the treatment mares following exercise (P<0.001) than the control mares, but progesterone concentrations were similar between groups.
It can be concluded that the exercise treatment did not induce deleterious effects on the early embryonic and fetal development of the treatment mares. Rather, aerobic exercise led to beneficial changes in uterine blood flow and embryonic vesicle size. Furthermore, the stressed state of the exercised mares did not have an impact on pregnancy loss or led to abnormal conceptus maturation. More research is needed to determine other physiological and hormonal changes that can be attributed to aerobic exercise during pregnancy in the horse.



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