Nutrient Deficiencies in Horse Feed Diets

Horses, like all animals, have a range of nutrient requirements to meet their daily needs.  These are spelled out as minimum nutrient requirements in the Nutrient Requirements of Horses, 6th Edition, published by the National Research Council of the National Academy of Science.

If these minimum requirements are not met, the horse may experience deficiency symptoms.  The severity of the deficiency symptoms may depend on the degree of the deficiency and the time period over which the deficiency exists. 

  • A sub-clinicaldeficiency may be the result of a small deficiency over a period of time. 
    • Subclinical deficiencies may also result in decreased immune response, decreased reproductive efficiency and decreased performance.
  • A clinical deficiency is present when there are readily observed or measured symptoms.

Perhaps the easiest example is a deficiency of energy (Calories) in the diet.  The more severe the deficiency, the faster the horse will lose weight.  If a horse is losing a quarter of a pound per day, the loss will take some time to be visible. Over the course of 6 months, the horse would lose 45 pounds or about a full body condition score.  Over the course of a year, the horse is almost 100 lbs underweight or goes from a body condition score 5 to a 3.

If the horse is getting sufficient Calories, but is deficient in protein or essential amino acids, the body condition might appear OK, but the hair coat might get dull, the hoof quality might deteriorate and the muscle tone might be lost.  This is common for horses that are on pasture that has adequate energy content, but is short on amino acids or other nutrients.  If the diet is deficient in key fat soluble vitamins such as A, D and E, it might take longer for the deficiency symptoms to show up as the animal will use up stored vitamins first.  If there are mineral deficiencies or imbalances the symptoms might show up in either bone problems or reproductive problems.

Mineral imbalances can create deficiency symptoms as well.  A diet that contains a large excess of zinc might produce symptoms consistent with copper deficiency.  An excess of phosphorus, creating an inverted calcium to phosphorus ratio (less than 1:1), can produce nutritional secondary hyperparathyroidism or “Big Head” disease as well as other bone issues.

The diet below illustrates a diet that might produce some sub-clinical issues over time.  This is a fairly typical grass hay and oat diet and uses basic NRC requirements for an 1100 lb horse at light work.

Percent of nutrient needs that are met with a traditional horse diet of oats and hay.

Offering salt free choice would take care of the sodium (Na) deficiency, but there would still be some trace mineral and vitamin shortages in the diet.  The extra magnesium in the diet would not be expected to be a problem.

Using a ration balancer horse feed product would be one solution. Using a properly fortified commercial feed that contains meets all of the requirements when fed as directed would also be a good way to prevent the development of clinical or subclinical deficiency symptoms.

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4 Responses to Nutrient Deficiencies in Horse Feed Diets

  1. Pingback: Nutrient Deficiencies in Horse Feed Diets | The Feed Room | Texas Horse Report

  2. Pingback: Feeding Foals | The Feed Room

  3. Susan Wolfson says:

    I have followed all vet and nutritionist recommendations trying to get my senior horse to put on weight. She just won’t. She is on high quality feed, with balanced nutrition, she has hay and grazing, she is by herself with no competition for the feed she gets. I also give her extra fat supplement in the form of flax pellets. She is pasture kept with a open stall available. She is not worked. She cribs but only when she stands at her feed bowl. Her blood panels and teeth inspection show no underlying problems. In the past it took free feeding hay and 18 lbs of feed split up in 3 feedings a day to keep her in good condition. This was when her prior owner had her and was working her regularly. The only thing I haven’t tried is moving her to a place where I feed her myself.
    Help!

    • Gina T. says:

      Hello Susan, It sounds like you’ve worked hard to figure out a plan for her. You may simply have to face the fact that she is going to take a lot of groceries to keep her weight on. Of course, keeping her where you feed her yourself might add some peace of mind for you as the owner!
      Thank you~ Gina T.

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