Case of the Month


Clinical presentation: 3 year old black & white mini filly, primary complaint of rapid weight loss in past month. Housed in barn at night with all day turnout. Paddock has minimal grass available. Diet consists of 1st cut hay, mineral/vitamin block and salt block all free choice. Mini lives with her pasture-mate, a 6 year old brown & white mini mare. Both ponies are current on vaccinations, deworming, and teeth were floated in December 2016. No history of pasture-mate being a food-hog, or overly aggressive in regards to hay.

Physical examination: auscultation of heart, lungs, and gi tract (for proper motility); palpation for enlarged lymph nodes, sore muscles, abnormal growths; examination of neurologic status and mentation – all results normal save the mini being thin- Body Condition Score of 3.5/8, and not having shed out her winter coat completely over trunk and body. There was a reasonable loss of muscle mass over the hindquarters, topline, and shoulders. All ribs were easily palpable. Mini did not seem overly dull, weak or depressed.

Several photographs were taken of both minis for comparison.



Note the poor hair coat and muscle atrophy over the scapula.

Bloodwork was taken to measure the following:

  • Complete Blood Count- Measures red and white blood cell amounts, as well as types of white blood cells. This ensures body is making enough red blood cells, and there are no signs of inflammation or infection.
  • Serum Chemistry- to ensure vital organs are functioning normally.
  • Thyroid level is a reflection of function.
  • Vitamin E level- an antioxidant that is directly related to muscle health, as well as total body health.

CBC, Chemistry, and T4 levels were all within normal ranges.

The Vitamin E level was very low. 70 ug with normal ranges going from 200-1000 ug in the adult horse/pony!

The mini was started on supplementation, as well as her pasturemate. Her levels will be rechecked in 45-60 days to ensure proper response to supplementation.


Discussion: How does vitamin E deficiency occur in a horse housed in good conditions?

Diet, primarily the lack of grass forage. Access to grass forage can be difficult to obtain depending on geographic location. This requires some horses to live on hay-centered diets. Unfortunately, hay routinely has poor vitamin E levels. The process of producing hay ‘bleaches’ it of its nutritional values. These values can be further depleted by being exposed to the elements, especially sunlight, for long periods of time. Fresh grass has acceptable levels of vitamin E, but if horse does not have sufficient amounts of grass, it cannot make up the deficit. Vitamin E is considered an essential nutrient because the horse lacks the ability to synthesize it in the body.

When hay is deficient and access to grass is limited, relying on feed/ration alone to provide the daily requirements for vitamin E is not enough. The recommended levels of daily intake will increase if horse is active in training or competition. That is why a supplement must be added to the diet. There are several quality supplements out on the market. The most bioavailable form that is recommended (University studies where they created low serum Vitamin E then supplemented to raise levels) is the d-alpha-tocopherol form. Natural form vs. synthetic form is best, and liquid is most readily absorbed.

While the clinical signs can be quite dramatic, this issue is readily treatable. Most horses respond quickly and are able to maintain normal levels on an oral supplement. We recommend checking serum vitamin E levels in horses that have limited to no access to grass on a yearly or biyearly basis, depending on their activity levels.


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