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Nutrition of the StallionBy Dr. Peter Huntington · March 28, 2012

Domestication of the horse has had the most dramatic effect on the environment and natural instincts of the stallion. The wild stallion runs with a group of mares, ranging far and wide in search of food, and protects them from capture by another stallion and from predators, so he is usually the fittest horse in the herd.

The domesticated stallion may never go hungry, but he is usually confined in a small area; fed two meals a day, often with only poor-quality pasture to graze; and locked away from contact with other horses. It is little wonder that some stallions have significant behavioral problems. Safe feeding practices that are compatible with fertility, behavior, and success in the show ring are based on pasture and high-quality hay, and use concentrate feeds and supplements only when necessary. Use body condition scoring (or weight) to monitor the suitability of the stallion’s diet. Keep the stallion in the range from moderate to slightly fat. A marked crest indicates a fat stallion.

In the nonbreeding season, the underfed stallion does not look his best for inspections by owners of mares, for photography sessions, or in the show ring, nor does he have enough energy to work well. During the breeding season he may tire easily and not maintain his interest in the mares. Vitamin A and E deficiencies have been linked anecdotally with reproductive disorders in stallions, but are likely to occur only if the stallion is fed a diet deficient in green forage and without supplementary vitamin A or E for an extended period. Selenium and manganese deficiencies have also been linked to reduced fertility.

It is a far more likely that the stallion is overfed energy or protein. A certain level of fat cover is important to provide energy reserves for work and breeding, but obesity is detrimental to fitness and fertility. Stallions that are too fat have a greater risk of dying while serving a mare, particularly early in the season, and are more likely to lose enthusiasm later in the breeding season. Overfeeding grain can lead to an increased risk of laminitis, colic, and diarrhea. Many stallions are fed more supplements than they need and are receiving high levels of vitamins and minerals. The imbalance of minerals can create relative deficiencies, and vitamin A toxicity from excessive supplementation can occur.

Nutrient Requirements During the Nonbreeding Season
The stallion has the same nutrient requirements as the average mare or gelding during the nonbreeding season, but stallions often hold their condition better. Normally, stallions can be maintained on pasture and hay. If pasture quantity and quality are adequate, the stallion may not need any supplementary feed, but a salt block should be provided. In cold weather, hay is the first choice of supplement to pasture. During winter when there is only poor-quality pasture, the stallion needs more hay to produce body heat during digestion, and you can feed hay ad libitum.

If a stallion is losing condition or needs to gain condition, first increase the hay intake up to 8–10 kg/day (17-22 lb). If this is not sufficient to produce the required change in condition, then add a small amount of grain to the diet; 2 kg (4.4 lb) of oats will supply more than one-third of the energy requirements of the stallion. Add a mineral and vitamin supplement to balance the diet when you are feeding grain.

If you are showing the stallion, both the daily intake and the concentration of energy, protein, minerals and vitamins in the feed will need to be increased. If you need to condition the stallion’s coat you can stable him overnight and during cold weather to reduce hair growth, or you can blanket him (a stallion with a fine hair coat will need to be blanketed anyway when in the paddock during cold weather). Feeding a small amount of polyunsaturated oil, sunflower seeds, or full-fat soybean meal will condition the coat.

Nutrient Requirements During the Breeding Season
During the breeding season the nutrient requirements of the stallion increase, but not as dramatically as many owners assume. They are similar to those of the late pregnant mare or a horse in light work, yet many people feed the stallion as though it were in heavy work. The breeding stallion will eat approximately 10% more feed, but has a 20% increase in requirements for energy, lysine, calcium, phosphorus, and magnesium, so the feed may have to be more concentrated. Vitamin A and E requirements increase by over 50%, but the requirement for other trace minerals is relatively unchanged. There is no evidence to suggest that supplementation of the stallion’s ration above these requirements increases fertility.

Oats can be mixed with a small amount of chaff, but it is more economical to feed most of the horse’s roughage intake as hay. Add a mineral and vitamin supplement that has high levels of vitamin E. Most supplements have adequate vitamin A content, but you may need to check the selenium content if the soils are selenium-deficient. Depending on the salt content of the supplement and the stallion’s consumption of a salt block, extra salt may be needed during warmer weather to counteract losses in sweat.

Some stallions are always difficult to handle, and others become hard to manage when mares are around. There are several feeding strategies to minimize behavioral abnormalities. First, cut down the grain intake and feed a relatively low-grain/high-roughage diet. Rice-based feeds can be fed instead of oats. Fat is very high in energy, but is not associated with behavioral problems, so you can add that to the diet.