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Oklahoma State University

Nutrition a key component to managing growing horses

Tuesday, May 8, 2018

Growing horses are just like human children in that sound nutrition is important to their physical well-being during their formative years, with resulting effects that can last a lifetime. (Photo by Todd Johnson)

Horse managers can learn a lot from mothers who tell kids to eat what is on their plates so they will grow up big and strong.

Generally, 50 percent to 60 percent of a horse’s mature weight is reached by 12 months of age, and 80 percent to 90 percent is reached by 24 months of age. These are the growing years, and a bit of applied “motherly concern” can last a horse’s lifetime.

Whatever the breed of horse, nutrition is a key component to managing for sound growth, reminds Kris Hiney, Oklahoma State University Cooperative Extension equine specialist.

“While nutrition may not overcome poor genetics or a poorly designed exercise program, studies show it can significantly affect the health of growing horses,” she said. “Level of intake and ration composition play important roles in altering rate and composition of gain.”

Research indicates restricting intake to achieve a slow increase in wither height during early growth leads to future problems if a young horse is later fed to abruptly increase its size or condition. In addition, final mature height of the horse may be affected if restriction of feed is extreme.

On the other hand, the rate of bone and muscle growth in horses slows as the animal matures. As a result, providing excess nutrition will result in more deposition of fat, a problem shared by certain two-legged mammals that travel in cars.

Hiney cautions horse managers to remember yearlings on high planes of nutrition are more susceptible than weanlings to laying down larger quantities of fat, and thus require close regulation of intake and exercise level.

“Maintaining young, growing horses in extremely thin conditions may limit sound skeletal growth later in life, while excess fat creates more weight stress on legs and reduces the horse’s athletic ability; the goal is to reach a happy medium,” she said.

The exact body condition and rate of gain needed to promote sound growth of muscle and bone is debatable, and perhaps even somewhat flexible.

“Individual differences in the genetic makeup of horses create so much variation that general recommendations are limited in scope and accuracy,” Hiney said.

Also, because there may be differences in the rate at which bone and muscle mature, it may be desirable for some horses to grow at slower rates than others to allow for a coordinated development of both bodily systems.

“In most cases, young horses should be maintained in moderate body condition to promote the proper development of bone and muscle,” Hiney said.

Visual clues tell the tale

Body condition can be estimated visually by observing fat cover on the horse’s body. Indications of a moderate condition are that individual ribs cannot be seen but can be easily felt, the area around the tailhead is slightly rounded in appearance and the backbone is level with surrounding tissue on the back and loin.

“Changes in body condition should be monitored individually because young horses differ in the amount of fat that is deposited at similar feed intake and exercise levels,” Hiney said. “Just remember estimates based on a ‘typical horse’ are exactly that, estimates.”

Weanlings expected to mature at 1,300 pounds typically will gain 1.5 pounds to 2 pounds per day. Yearlings will gain less, 1 pound to 1.5 pounds per day. Two-year-old horses should gain 0.5 pound to 0.75 pound per day.

To support moderate growth, nursing foals may consume between 1 pound and 1.5 pounds of creep feed per 100 pounds of body weight a day. Weanlings may consume 1.5 pounds to 2.5 pounds of grain mix per 100 pounds of body weight a day. Yearlings may consume 1 pound to 2 pounds of grain mix per 100 pounds of body weight a day.

Hiney cautioned horse managers need to be particularly careful with nutrient supplies when feeding a horse for rapid growth, as skeletal and cartilage issues can easily arise.

“There is some indication that feeding high-starch diets with a high glycemin index may not be the best thing for cartilage formation,” she said. “Slow and steady is ideal for long-term health.”

Remember, estimates are only a baseline, as the level of exercise will affect a horse’s nutrient requirements. Nutrients in the feed must be balanced with each other to ensure the individual horse’s needs for energy, protein and minerals are met.

Most weanling grain mixes contain between 1.3 and 1.5 mega-calories of digestible energy per pound. To ensure the ration supplies adequate protein and minerals for these energy densities, grain mixes for weanlings and yearlings should contain between 12 percent and 14 percent crude protein, 0.6 percent calcium and 0.4 percent phosphorus.

“Rations should be combined with high-quality hay,” Hiney said. “Keep in mind the amount and nutrient content of the hay will affect the amount of nutrients needed in the grain mixes.”

Feedstuff evaluation and paperwork

Evaluations of rations fed to growing horses should include checks of nutrient-to-calorie ratios.

“There are many minerals that can cause growth problems when fed in either deficient or excessive amounts,” Hiney said. “As high levels of some minerals may interfere with absorption of other minerals, it is important to avoid over-supplementation.”

Mineral supplements are not necessary when feeding most commercially prepared rations formulated for growing horses because these mixes already have been supplemented. Rations using hays and grains that are not supplemented typically will be below the recommended levels for zinc, copper and sodium.

Vitamins also are a concern. Commercially prepared grain mixes usually will already be supplemented with vitamins A, D and E, as well as several B vitamins.

“Horse managers feeding grain mixes that have not been supplemented should add a vitamin premix that includes these vitamins,” Hiney said.

Nor should horse managers overlook one of the most important aspects of a nutritional plan: record keeping.

“Records on weight changes, body condition, nutritional level and health status will provide a framework for management decisions, both for the individual horse and for future generations of growing horses that come from the line,” Hiney said.

Hiney recommends that horses be assessed every two to three weeks.

Additional information on the nutritional needs of growing horses is available through all OSU Cooperative Extension county offices, typically listed under “County Government” in local telephone directories.

By Donald Stotts

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