Written by: Shannon Pratt-Phillips, Ph.D.

How nutrition impacts soundness in all stages of life.

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Nutrition affects every aspect of equine health – from ensuring sound bone development during growth, providing energy for athletic work, supporting hoof and joint health, and in the prevention of many disease processes. As such, nutrition has a profound impact on the soundness and usefulness of the horse.

Early equine life

Starting from the moment the mare conceives, her nutritional status will affect the foal’s development. In addition to the obvious increased needs for energy, protein, calcium, and phosphorus (these latter two for bone growth) during pregnancy, copper intake by the mare has been shown to be vital to decrease the incidence of developmental orthopedic diseases in foals.

Once the foal is born, the mare should be fed to maintain her milk supply, and creep feed should be introduced once the milk production wanes. Growth rate should be carefully monitored, as too-rapid growth, often due to an overconsumption of calories and/or protein, can also predispose a horse to developmental disorders. Of particular concern is physitis, swelling around the growth plates of the long bones in young horses, frequently seen in fast-growing, top-heavy foals pastured on dry, hard ground.

In young horses, protein quality (amino acid makeup) is as important as total protein quantity intake, so it is important to select feeds rich in key amino acids such as lysine, which is plentiful in soybean meal. A young horse that has been fed correctly during growth to achieve its genetic conformation potential will be more likely to maintain soundness into adulthood.

The building years of your horse’s life

In the early stages of a horse’s career, calcium and phosphorus are of particular importance to support the bone remodeling that occurs with the concussive impacts of exercise. A balance of two parts calcium to one part phosphorus is ideal (although 1.1:1 to 6:1 is also fine), but the horse should also meet its minimum intakes. While most horse people tend to be careful about calcium intake for their horses, low-phosphorus hay is common and can be problematic. Getting your hay tested is the best way to ensure these minimum-to-ideal values are met, even when feeding high-quality grain mixes.

Biotin has been proven to improve hoof quality in horses with poor hooves, although copper, zinc, and methionine are also believed to play a role in hoof health. There are no nutrients proven to impact tendon and ligament strength, although a solid diet providing all of the horse’s nutrient requirements is vital.

Similarly, joint health may be aided by some non-nutritional compounds such as chondroitin sulfate or hyaloronic acid, which are found in many supplements. However, the components of these compounds – namely sulfur, galactose, and amino acids – are already present in most equine diets.

There is some confusion as to how to maintain ideal muscle strength, which could impact movement and soundness, via nutrition. Muscle cells are built and strengthened through exercise, and their growth is supported through nutrition. However, simply feeding a diet high in protein or specific amino acids will not cause a horse to build muscle or topline, just as we know not to eat egg yolks and expect abs of steel! Any amino acid deficiency in an adult horse would be quite rare, as most horses already consume far more protein than required. Poor muscle quality is typically due to genetics, conformation, or lack of proper exercise.

Vitamin E and selenium are commonly fed to help preserve muscle in the face of intense exercise, although research has not found any overall benefit. That said, while vitamin E is relatively non-toxic and its anti-inflammatory properties may be helpful, selenium intake can reach toxic levels when supplemented if the owner is not careful. Selenium is already added to horse feeds, so if it is included in multiple supplements or found in high quantities in hay or grass (this is where a hay analysis is useful), it can be easy to reach problematic levels of intake.

Muscle, joints and tendons may also be maintained with omega-3 fatty acid intake. These fats are well-recognized to provide some immune support and some anti-inflammatory properties and therefore can influence soundness. A good source of omega-3 fatty acids is linseed oil (flaxseed oil) but if you want the best of the omega-3s, DHA and EPA (fish oil) is the only direct source.

The equine senior citizen

As the horse ages, good nutrition can help keep an equine athlete active well into its twenties. Vitamin C intake becomes important in older horses, as they are less able to manufacture it due to decreased liver function, a decline in hindgut microflora, or dysfunction of the pituitary gland.

Dental health is probably one of the most important considerations for older horses to ensure they can chew the food that will provide them with their required nutrients. Regular checkups should be scheduled to detect sharp points, infections, lost or fractured teeth and take remedial steps. In some cases, a more easily chewed, digestible diet may have to be introduced.

Maintaining a horse’s ideal body weight is important at any age, but especially for older animals. Avoiding obesity in a horse as it becomes less active can be a challenge, but horses that carry too much weight will be putting additional strain on their hooves, joints, tendons and ligaments over time. This additional strain can contribute to lameness, including an increased risk of laminitis, which can also be nutritionally triggered by carbohydrate overload.

Tailoring your horse’s diet

Luckily, most equine diets are already packed with many of the nutrients necessary to promote soundness. Of course, fresh clean water, high-quality forages (hay or grass) and a salt source can meet the needs for most horses. Good quality hay (even 8-10% protein) can provide even an active horse with most of its calorie, protein, calcium, phosphorus, potassium, magnesium, and many micromineral requirements. If the hay has been stored well and for not more than a year, it should also provide vitamins A and E.

Horses in higher levels of work will need fortification of their diet with calories, which often comes in the form of cereal grains and/or fats. Grains and commercial feeds will also provide additional protein, minerals, and vitamins. Most commercial feeds are fortified with sufficient amounts of all remaining nutrients for the type of horse for which they are designed. Depending on the horse’s needs and his feeds, additional supplements of omega-3 may be warranted, although these are often now added to many commercial feeds.

Similar to your pediatrician or doctor recommending that you see a dietician, your horse might benefit from a visit from an equine nutritionist to ensure that its requirements are met. Understanding how nutritional needs can change over the course of your horse’s life can help ensure it remains healthy and sound throughout its career – and beyond.