Young horses: Feeding for healthy bones

Table of Contents: Mare nutrition; Creep feeding; Exercise; Genetics; Protein; Carbs; Insulin and thyroxin; Minerals; Stress; Formulating a diet; Resources
Developmental bone problems are very common in young horses. In a sample of 500 foals, researchers found the incidence of OCD to be 25-30%. While surgery can correct OCD, there is a chance the lesions may be inoperable, and the surgery itself carries risk. Given the costs and complications of bone problems, good feeding and foal management practices are a wise investment.

Mare nutrition
Healthy foals start with healthy mares who have had proper nutrition to support the growth of the in-utero foals and the newborn foal. For the first three months babies rely on mother's milk for their nutritional needs, including vitamins and trace elements that promote healthy bone growth. It is possible to have the mare's milk analyzed, and if necessary mare's milk can be supplemented with special additives -- Rejuvenaide is one such additive that can be administered daily. Many farms analyze milk on day 4 and week 4, 8, and 12. For more information on mare nutrition, see these articles.

Creep feeding
At about three months, foals begin to produce enzymes that allow for the digestion of starches, and at that time foals benefit from "creep feeding" milk pellets on a free choice basis. This helps prepare their tummies for the transition to concentrated feeds. Studies show that creep-fed foals are healthier and experience fewer problems with limb development.

"Baby food" must have high concentrations of nutrients because foals have such small bodies they cannot consume much food. As they grow and take in more food, the percentage of nutrients can level off. At six months, babies begin to consume increasing amounts of forage. By the time they are yearlings, they should be consuming predominantly forage.

Causes of bone development problems
Nutrition, exercise, breeding and foal management practices, and genetics are important variables in predicting which foal is at risk for bone disorders.

Exercise
Studies show that regular exercise is critical to bone development. Foals that get plenty of exercise have significantly less OCD that those on restricted turnout. Confinement is particularly damaging when coupled with overnutrition/overfeeding. In a study carried out in Germany, 30% of foals with 5 hours/week of exercise had fetlock OCD, compared to only 16% of foals with 20 hours of exercise a week. Foals born early in the year are often stalled due to bad weather; they get less exercise and tend to have more OCD. Irregular exercise (being stalled for a few days and then turned out) can stress the joints and result in developmental or traumatic joint issues. Excessive exercise is also detrimental to the growing foal.

Genetics
Genetics partly determines how bones develop. In a Danish study of eight stallions and their offspring, one stallion's offspring had a very high rate of OCD, although his own radiographs were clean. One large study reported findings that mares with OCD tend to have more offspring with OCD -- 27% of babies of OCD mares had OCD, while only 11% of foals of non-OCD mares had OCD.

Protein
While protein has gotten a "bad rap" for causing developmental bone problems, research shows that crude protein amino acids DO NOT cause OCD. Most nutritionists recommend feeding a diet of 15 to 16 percent crude protein to foals, 13 to 14 percent crude protein to weanlings, and 10 to 12 percent crude protein to yearlings (these amounts are for the total diet, not just the concentrated feeds). Increased incidence of OCD lesions have been noted in horses fed 130% of what the National Research Council recommends for carbohydrates and protein. As proteins have more or less been ruled out as a direct cause of DOD, carbohydrates are the prime suspect here.

Carbs
Young horses fed excessive amounts of carbs are heavier and bigger. While studies don't always agree, there is at least some evidence that heavy/large foals are prone to OCD. In a Swedish study, hock OCD was found to be linked with foals which had a larger than average birth weight, large skeletal frame, and demonstrated a higher average daily weight gain. Experts do agree that the growth spurts are undesirable; the growing process should be steady and regular. Overfeeding for rapid growth or underfeeding to slow growth can both put a young horse at risk for bone problems. In short, practice moderation in feeding to minimize growth spurts and ensure adequate nutrient levels. Many vets recommend regularly measuring and weighing babies to assist in regulating growth.

Insulin and thyroxin levels
High energy sweet feeds and concentrates are usually the cause of excess digestible energy. When hay is digested, it is broken down into fatty acids; grain is broken down into sugars. Sugars influence the balance of insulin and thyroxin in the body, and excess thyroxin carries increased risk of OCD. It's possible that some foals are glucose-intolerant and/or insulin-resistant. If such foals were placed on a high-carb diet they would theoretically be more prone to OCD. See this article in California Thoroughbred for more information.

Minerals
Calcium, phosphorus, copper, zinc must be fed in adequate amounts to promote healthy bone. Calcium is necessary for calcification of cartilage while both calcium and phosphorus are needed for the formation of subchondral bone. Copper promotes cross-linkage of collagen fibers used as the core for subchondral bone.

Some facts about these nutrients:

• The calcium to phosphorus ratio should be about 1.5 to 1. High phosphorus levels (where there is more phosphorus than calcium) have been implicated in OCD lesions, and one study did consistently produce lesions in young foals fed five times the NRC level. Slightly elevated calcium levels have no detrimental so long as the proper ratio to phosphorus is maintained. Very high amounts of calcium have been shown to interfere with the absorption of copper, zinc, and phosphorus.
• Copper levels are important, but most feeds now include sufficient levels ofcopper. Studies show a higher incidence of lesions in foals with low-copper diets in the vertebrae, but not the limbs. It is hard to overfeed copper.
• Zinc and copper levels should be jointly determined. A copper to zinc ratio of about 1:4 is desirable. If copper levels are raised in the diet, zinc levels should be raised too.
• A deficiency of zinc impairs protein and energy utilization which impacts cartilage development.

For more information, see the book Care and Feeding of Horses on Google -- there is a chapter on Vitamins and Minerals.

Stress
Anything that stresses a foal can increase the likelihood of developmental bone problems. Stressed animals produce cortisol, and cortisol inhibits the creation of bone tissue. Weaning is a high stress period in a foal's life, and it is also a time when their nutrition might be compromised. Other possible stresses include pain, separation from mother, prolonged fear/excitement, and confinement.



Formulating a diet
The easiest way to do plan your foal's feeding program is to go to contact a nutritional consultant at a reputable feed company and ask for assistance. Progressive Nutrition has an excellent reputation and competent specialists that assisted me. I have emailed head nutritionist Don Kapper and received an answer within an hour (of course I can't promise anyone will be that lucky). Choose a company you trust and follow their guidelines. Ask a local breeder with a good track record for healthy foals if you don't have a company in mind.

Folks who want to be more hands-on in their horse's nutritional program should read the Kapper article (part I) below, and also this article chapter on growing horses in the book Feeding and Care of the Horse.

RESOURCES

Nutrition of the Growing Hanoverian Part I by Don Kapper, Director of Nutrition at Progressive Nutrition

Nutrition of the Growing Hanoverian Part II by Don Kapper, Director of Nutrition at Progressive Nutrition

Feeding the Young, Growing Horse for Optimal Skeletal Development

Articles on DOD in The Horse magazine