Dennis H. Sigler, Ph.D.
Horse owners and trainers who want to compete in today’s performance horse industry must be aware of all factors which affect ultimate performance in the arena or on the track. Nutrition of broodmares (even the recipient mares) and feeding of the developing equine athlete after weaning is often a neglected area of care and attention. If we expect optimum performance, nutrition of the mare during the last 90 days of pregnancy and after foaling and feeding of the young growing horse between 6 months to two years of age must be managed carefully with consideration to future soundness and longevity.
Since these horses are potential future athletes, proper skeletal development is of utmost importance. One of the major problems in the horse industry is injuries and unsoundness in young horses. Developmental orthopedic disease (DOD) is a reality in all segments of the performance horse industry and is likely related to the high incidence of injury and skeletal failure in young working horses. Many of our high-profile events in both racing and show horses involve immature horses which are less than 3 or 4 years of age. It is imperative that these young horses get the very best nutritional balance during their early developmental stages.
Balanced nutrition of the mare during the later stages of gestation and in early lactation is a basic requirement for optimum skeletal development of the foal. Mineral intake, especially during that critical last three months, is the first step in assuring a sound skeleton. For mares on pasture, providing free-choice mineral with a 1:1 Ca to P ratio such as a high quality 12:12 mineral is a must. Trace minerals also are very important. The mineral mix should contain at least 1500 to 2000 ppm of copper along with adequate zinc and manganese.
For the growing horse proper balance of protein and energy is one of the keys. Growing horses require high quality protein, which means a balance of required amino acids. Specific amino acids are required by the young animal for protein synthesis and proper growth of muscle and skeletal tissue. Assuring adequate lysine intake is important for growth. However, the total balance of all amino acids is important and other amino acids such as threonine and likely, methionine and cysteine also affect growth and development of the skeletal system. Because of this, young horses need a high-quality protein source in the diet. For the weanling up to 1 year of age, when feeding grass hay, a diet containing at least 16% crude protein from high-quality sources such as soybean meal or milk proteins is recommended. If young horses are fed alfalfa hay, lower protein concentrates can be fed, but mineral balance is more critical.
The other side of the equation, energy intake is another key to proper development while reducing the incidence of DOD. It is important to assure adequate skeletal growth without creating excess body weight or fat deposition. This is the reason diets should be formulated based on nutrient to calorie ratios. It is recommended to assure that protein requirements are slightly above actual needs while keeping energy intake to a minimum level. The age-old practice of feeding straight oats and hay to young horses demonstrates the importance of keeping the nutrient-to-calorie ratio in check. Research has shown that young horses on this type of unbalanced feeding program will get fat, but will suffer from inadequate skeletal development. Likewise, producers should be cautious about adding additional fat to an already balanced diet. This scenario may significantly increase the calorie intake without increasing the intake of other nutrients required for rapid growth such as protein, calcium (Ca) and phosphorus (P). Also, keep in mind that diets which are adequately balanced for a slow or moderate rate of growth, may become a real problem if fed at levels to attain rapid growth rates. In this case, protein, and mineral balance becomes even more critical to help prevent DOD. Since bone is made up primarily of protein, Ca and P, the right balance of these minerals in relation to the energy intake is critical. Ca makes up about 34% of the total mineral content of the skeletal system, while P makes up about 17%.
Since bone strength does not peak until about 5 years of age, it is imperative to make sure young horses have adequate Ca and P intake for the first several years of life. Ratio of Ca to P is also important and that ratio should be between 1.5 – 2.0:1, Ca to P. If Ca levels reach levels which are over 3:1 ratios, P absorption may be impaired. This is one of the problems often encountered when horses are fed straight alfalfa hay or cubes with no additional P supplementation. Young horses on this type of feeding program are predisposed to skeletal development issues. Young horses should be fed a mixture of alfalfa and grass hay to help improve the Ca:P balance. Also, feeding a high-quality concentrate which has the right Ca and P balance for the type of hay being fed is a safeguard to assure adequate Ca and P intake.
In addition to Ca and P balance, several trace minerals such as copper, zinc and manganese play essential roles in bone and cartilage development. Not only is adequate intake of these minerals essential, but the balance of one mineral to the others is important as well. Horse owners should feed a high-quality concentrate which has been formulated for growing horses along with a good quality forage and should avoid diluting it with oats or other feeds. Just as dangerous is the over supplementation of additional additives that may change this critical balance and lead to DOD issues.
Vitamin A and Vitamin D both are involved in growth and skeletal development and have minimum requirements for all horses. Most high-end horse feed products contain more than adequate levels of these important vitamins. Over-supplementation of both vitamins can lead to toxicity issues, so once again, feed a balanced concentrate and do not supplement with other additives unless directed to do so by a qualified nutritionist. Adequate vitamin E in the diet is essential for overall health and immune response, so important for the young horse, especially those in high-stress situations such as fitting for show or sales.
In summary, total nutrient intake, from conception to maturity, is critical for optimum skeletal development in young horses. Not only is proper development essential for soundness during the formative years, but likely determines longevity and ultimate usefulness of horses as they get older. When providing the level of protein and energy intake which promotes maximum growth and development, the nutrient balance of the total diet is even more critical. Mineral intake, including Ca, P and trace minerals, is also critical and can be affected by the forage portion of the diet. Feeding a high quality, properly formulated concentrate with good quality forages, paired with proper exercise programs, will certainly help mitigate developmental problems in young growing horses.
Dr. Dennis Sigler is a retired Professor and Texas A&M University Extension Horse Specialist. He has previously worked as an animal nutritionist for several different livestock feed companies. He currently serves as the Horse Nutrition Specialist for Martindale Feed Mill and does nutritional consulting work for individual horse farms, ranches and companies. Dr. Sigler is also an AQHA and NRCHA-Approved judge and in his spare time, he trains and shows cutting, cow horse and stock horses.