For those in the breeding industry, much time is focused on the care and management of broodmares and their offspring. Stallions also need consideration to keep them at their peak performance in the breeding shed. Following is information on the importance of vitamin E for the breeding stallion from Kentucky Equine Research.
Vitamin E is an important antioxidant, as are selenium and vitamin C. Nutrient Requirements of Horses (Sixth Edition, 2007) recommends 500 IU of vitamin E per day for 1,100-pound (500-kg) stallions that are not breeding and 800 IU/day for breeding stallions. The vitamin E requirement for stallions that are not breeding is the same as for other horses that are not in work. The requirement of 800 IU/day for breeding stallions is the same as that recommended for pregnant mares, but lower than the requirement for horses in heavy exercise (1,000 IU/day). Vitamin E requirements for optimal immune function and for horses with neurologic disease are likely to be higher.
Vitamins E and C are important antioxidants needed by sperm cells. Sperm cell membranes contain a high concentration of long-chain polyunsaturated fatty acids, which makes them susceptible to oxidative damage. Several steps in sperm cell maturation and eventual fertilization can produce reactive oxygen metabolites that can damage sperm cells or decrease their motility if antioxidant defenses are depleted.
One study evaluated the effects of vitamins E and C and other antioxidants on semen quality in pony stallions. Antioxidant supplementation did not have any effect on sperm motility (either overall or progressive in a straight line) or longevity when cooled and stored for 24 hours. However, there was a slight, but statistically significant, reduction in the percentage of abnormally formed sperm cells. The authors concluded that it is questionable whether the minor improvement in semen morphology following antioxidant supplementation might lead to improved fertility. These findings agree with a previous study that found the addition of antioxidants to semen extender to cooled equine semen did not have any significant effect on semen motility.
Horses that have decreased access to good-quality green pasture or hay will benefit from vitamin E supplementation to prevent possible vitamin E deficiency. Several equine neurologic diseases and some cases of tying-up have been associated with vitamin E deficiency. Because many stallions are managed in smaller paddocks and may be kept stalled longer than other horses, it is important to be mindful of possible vitamin E deficiency due to inadequate pasture grazing or feeding deficient hay.
Natural-source vitamin E is superior to synthetic vitamin E. For maximal absorption, micellized vitamin E should be used throughout the breeding season or year-round for optimal antioxidant protection.