A mistake some horse owners make is underfeeding their horses. This is often a misunderstanding by the owner on how much to feed their horse.

We commonly see this with fast-growing horses or overweight horses; owners will underfeed these types of horses to reduce energy (calorie) intake to slow growth rate or encourage weight loss. While the reduction in calories may be necessary, the difficulty arises with the reduction of essential nutrients (vitamins, minerals, amino acids), particularly when a feed is fed at a lower rate than what the feed manufacturer recommends. This can lead to malnourishment, poor performance, and health disorders.

The daily nutrient requirements for horses have been established by the National Research Council and are published in the Nutrient Requirements of Horses. These standards have been established after multiple years of research and are recognized worldwide. Thus, horse feeds are created using these guidelines to meet or exceed a horse’s daily nutrient needs.

For a comparison, some of the nutrient requirements per day for an 1100 lb (500 kg) horse would be:

  • An idle horse in no work:
    • Digestible Energy- 16.7 Mcal
    • Crude Protein- 630 grams
    • Lysine (limiting amino acid)- 27 grams
    • Calcium- 20 grams
    • Phosphorus- 14 grams
    • Zinc- 400 milligrams
  • A horse in moderate work:
    • Digestible Energy- 23.3 Mcal
    • Crude Protein- 768 grams
    • Lysine (limiting amino acid)- 33 grams
    • Calcium- 35 grams
    • Phosphorus- 21 grams
    • Zinc- 450 milligrams

This demonstrates how daily nutrient requirements differ across horses in different levels of work. What you would feed an idle horse would be inadequate to meet the needs of a horse in moderately-intense levels of exercise.

So, how do we ensure we aren’t underfeeding our horses? A horse’s diet always starts with high-quality forage. This can either be pasture or hay. The forage portion of a horse’s diet should be at least 1% of their body weight per day, with most recommendations 2% or above. For an 1100-pound horse, this would be 11 pounds or 22 pounds of forage per day, respectively. Yet, forage alone does not meet a horse’s daily nutritional needs and diets need to be supplemented with a ration balancer, at minimum.

There can be many reasons horse owners underfeed a horse feed. One common mistake is feeding horse feeds by volume (scoops or flakes) and not by weight. Flakes of hay will weigh differently based on the type of hay it is and harvest conditions. Feeds will weigh differently not only based on their nutrient content, but also how they are made. For example, the single quart weights for some of our feeds are:

More can be read on this in our Feed by Weight, Not by Volume article.

Another common way horse owners unintentionally underfeed their horses is by not following the feed manufacturer’s directions for feeding that product. Feeding less than what is recommended will lead to inadequate nutrition.

Underfed horses will develop nutrient deficiencies. The most obvious deficiency is energy (calories), which, if underfed, will lead to weight loss and can also lead to loss of performance or lethargy. Underfeeding also leads to essential nutrient (non-calorie) deficiencies. An example of this would be protein, or the appropriate amino acid balance. In our Building a Horse’s Topline article, we discussed the importance of certain amino acids (lysine, methionine, threonine) in the diet to ensure proper muscle growth and repair. Thus, underfeeding protein will lead to a poor topline and muscling, as well as decreased performance.

Other nutrient deficiencies can lead to serious health consequences. For example, if the following minerals and vitamins are underfed, they can lead to:

  • Selenium- hair loss, poor hoof quality, muscle breakdown, compromised immune system
  • Calcium- poor hoof quality, increased lameness, weakened bones
  • Phosphorus- weakened bones, muscle weakness
  • Copper- weakened bones and joints, dull coat, anemia
  • Potassium- muscle weakness, exercise intolerance
  • Zinc- poor hoof quality, weakened bones, dull coat, insulin resistance
  • Vitamin A- compromised immune system, weakened bones, night blindness, muscle weakness
  • Vitamin D- stiff and swollen joints, exercise intolerance, lameness
  • Vitamin E- muscle weakness, compromised immune system

There are other nutrient deficiencies observed in horses, as well. However, when feeds are added to the horse’s diet and fed at the manufacturer’s recommendations, these are usually avoided. Please contact us for any advice and support that you may need in designing a feeding plan for your individual horse, as we can ensure your horse is receiving the proper nutrition they need to support their health and well-being!
 

Chris J. Mortensen, Ph.D.