Exercise may affect reproduction in mares
New research has indicated competition mares in work may find it more difficult to conceive than those receiving little to no exercise.
Researchers at Clemson University and the University of Florida divided the mares into three groups; those receiving no exercise, partial exercise, and full exercise. Mares in the partial exercise group received 30 minutes of exercise per day in the lead up to ovulation and then rested for seven days once the egg had been released. Those in the full exercise group received 30 minutes exercise per day throughout the whole cycle.
Researchers measured the embryo number and quality, and levels of the hormone cortisol, which is known to suppress the reproductive cycle. The mares being exercised had higher levels of cortisol in the blood, which suggests reduced reproductive capability.
Embryo recovery rates were reduced, though the difference between the two exercise groups was not significant. The partial exercise group was also found to have the lowest embryo quality. Co-author of the study Christopher Mortenson said:
“This led us to conclude that exercise was just as detrimental, if not more so, in the time period just prior to and during fertilisation.”
However, breeding expert Dr Jonathan Pycock warned: “The study raises some interesting points, but in practice there are a lot of variables to consider.
“In my experience most sport horses benefit from being in regular exercise prior to breeding.”
The BSAVA has opened submissions for the BSAVA Clinical Research Abstracts 2026.
