Stallion Health and Season Affect Semen, Breeding Success

Vitamin E supplementation supports male reproductive health. In stallions, vitamin E stabilizes the plasma membrane of the sperm, which is necessary to penetrate the egg, and squelches damaging free radicals. Even if sperm are healthy and motile, other factors can affect the reproductive success of a stallion, including the time of year.

In general, semen quantity and quality in stallions changes markedly throughout the year.^* “For example, total sperm volume is often high in the autumn months, but progressive motility and the number of sperm with intact plasma membranes tend to be highest in the spring,” explained Clarissa Brown-Douglas, Ph.D., a nutritionist with Kentucky Equine Research.

Significant differences between individual stallions occur, though, and this variation precludes making generalizations about optimal breeding times. Some stallions have normal sperm motility year-round, while others actually have greatest sperm motility in either the spring or winter months.

As a result, researchers recommend considering each stallion individually to identify the ideal season in which they should be used for collection and preservation, thus optimizing breeding management of the stallion.

Nutritional management of stallions offers additional challenges for managers.

“Breeding stallions should be fed a balanced ration year-round, with adequate levels of all essential nutrients and enough calories to maintain body condition without becoming overweight. Stallion owners may consider having their horse’s diets analyzed both during the breeding season and off-season,” advised Brown-Douglas.

“During the breeding season, stallions require approximately 20% more energy, lysine, calcium, phosphorus, and magnesium than in the off-season, and a 50% increase in vitamins E and A,” she said. “Nano-E, a natural vitamin E supplement offered by Kentucky Equine Research, is an effective way of supplementing vitamin E to stallions during this time.”

^*Crespo, F., R. Wilson, M. Díaz-Jimenez, C. Consuergra, J. Dorado, B. Garcia Barrado, J. Gosalvez, R. Louis Smit, M. Hidalgo, and S. Johnston. 2020.  Effect of season on individual stallion semen characteristics. Animal Reproduction Science. doi:10.1016/j.anireprosci.2020.106641.