19 Apr 2022

Supplementing for the Competition Season

Did you know that the rate at which your horse breaks down nutrients and converts it to energy is dependent upon the amount of activity they do??

The process from which they obtain energy from food is called oxidation.  It is this process that converts the nutrients within food into energy that horses use for their day-to-day function.  How quickly this process occurs is completely dependent upon the amount of activity a horse is undertaking.  When they are at rest the rate of oxidation is at its lowest.  However, at times of stress (when stabling away at a competition perhaps), during exercise, during pregnancy (and lactation), or even when they’re young and still growing, the body requires a greater level of nutrients than the oxidation process is therefore far higher.

It is during this process that oxidative stress can occur.  A phenomenon as the result of the horse’s system becoming overwhelmed during oxidation, and an indication that the horse may be running low on antioxidants, or high on the more unstable reactive oxygen species (ROS) molecules.

The ROS molecules are needed for the horse’s immune system to work correctly, however, large quantities of these circulating free radicals, as they are also known, can cause tissue damage and lead to the destruction of healthy cells.  In turn, this could lead to

  • a decrease in immune function,
  • lameness due to the destruction of muscle tissue, and
  • other nervous system related problems.

This is where antioxidants jump in and save the day!

The Role of Antioxidants

Researchers at Rutgers University i agree that Vitamin E is the most important antioxidant. It protects the delicate cell membranes from damage by free radicals.

Vitamin E has not only been proven to help prevent horses tying up, but also supports muscles and performance during periods of strenuous exercise.

Vitamin C is another essential micronutrient that all animals need to function.  When horses are in good health and working at a moderate level, the horse’s liver can produce the required level of Vitamin C to maintain their health.  However, when a horse is stressed, (e.g. traveling, stabling away, or period of intense exercise), the production of Vitamin C can’t keep up with the demand placed on the horse’s body.

In this instance, supplementation can help decrease the effects of stress on the horse’s immune system.

Supplementing Antioxidants

The antioxidants Vitamin E and C both have a protective action against the damage caused by the free radicals expelled during the oxidation process:

  • hunting them or deactivating them,
  • preventing excess amounts of free radicals to be produced, and/or
  • stimulating the repair of damaged tissue and cells.

A healthy, balanced diet for the horse needs to deliver the necessary nutrients and essential vitamins and minerals, that are key to keeping the antioxidant balance positive.

Many forages and grasses are naturally high in Vitamin E. However, the age of the plant, heating, bailing, grinding, and drying for hay will decrease the Vitamin E content.

When supplementing with extra Vitamin E, owners should ensure that it is combined with a commercially available feed with added fat, or a separate fat source like oil or rice bran, as vitamin E is fat soluble.  This allows it to be fully absorbed and utilised by the horse’s body.

Vitamin E supplements in high amounts are not toxic to horses, but large doses (> 5,000 IU/day) should be carefully monitored as it may interact with other nutrients in the horse’s diet.

Rosehips have the highest Vitamin C content among horticultural crops, fruits, and vegetables, and offers a source of vitamin E in the top 36% of all food groups. Making it the perfect supplement for horses young and old, broodmares and competition horses alike.


i Carey A. Williams, Ph.D., Equine Extension Specialist Lesleyann E. Atherly, Rutgers University, School of Environmental and Biological Sciences, Animal Science Research Student Jessica D. Hirsch, Rutgers University, School of Environmental and Biological Sciences, Animal Science Research Student Fact Sheet #1065 – Published August 2007 OXIDATION AND OXIDATIVE STRESS

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