Vitamin E loss in hay

Hay can lose up to 75% of its vitamin E in 3 months of storage.

Vitamin E

Vitamin E has roles in immune response, nerve and muscle function. Vitamin E is also a well-known antioxidant. There are several different forms of vitamin E, with the most commonly known one being α-tocopherol. Vitamin E gets incorporated into cell membranes where it works by protecting unsaturated lipids (fats) and other cell membrane components from oxidative damage caused by free-radicals and reactive oxygen species. 

Vitamin E Deficiency

There are several different muscular and neurological diseases that are linked to vitamin E deficiency. White muscle disease, also known as nutritional muscular dystrophy, is a non-inflammatory degenerative disease that affects the muscles and hearts of foals from birth to 11 months (1). Vitamin E deficiency, along with selenium deficiency, have been implicated in white muscle disease. 

Equine motor neuron disease (EMND) is a neurodegenerative disorder of the lower motor neurons in horses ages 2 and older (1). EMND is characterized by muscle trembling, constant shifting of weight on the hind legs when standing, long periods of laying down, and muscle wasting. Evidence suggests EMND can manifest after a prolonged period of vitamin E deficiency. 

Equine degenerative myeoencephalopathy (EDM) is a degenerative disease of the spinal cord and select parts of the brain in young horses. Vitamin E deficiency in combination with a predisposing genetic factor is implicated in the development of this disease (1). 

Vitamin E and Fat in Diets

Additional fats and oils added to a horse’s diet require additional vitamin E supplementing in the diet to protect those fats and lipids from oxidative damage (1). 

Vitamin E and Exercise

Exercise increases a horse’s need for vitamin E as the process of exercise creates an environment inside the muscles that requires a higher quantity of antioxidants, like vitamin E, to help ensure proper muscle function and reduce oxidative damage. Exertional rhabdomyolysis (one cause of tying-up) may possibly be benefited by having additional vitamin E in the diet to help protect the muscles from damage caused by exercise. 

Testing for Vitamin E Deficiency

Blood serum vitamin E tests are the most common way of testing for a vitamin E deficiency in horses. However, this is not a common test performed at veterinary clinics so blood samples need to be sent off to a lab. Blood serum vitamin E tests usually reserved for suspicion of diseases such as EMND to see if the blood serum vitamin E levels are below normal healthy levels. 

Vitamin E Loss in Hay

Naturally occurring vitamin E declines over time in stored feeds. In alfalfa alone you can lose 54-73% of the vitamin E content in the first 12 weeks of storage at 30°C (1). Timothy hay can lose up to 60% of its vitamin E content during he four day drying period before it is even baled. Additional vitamin E losses occur the longer hay is stored and by the end of winter the quantity of vitamin E in your hay could be almost completely gone.

Supplementing Vitamin E

Horses that are fed hay and processed forages should be supplemented with vitamin E to compensate for the loss of vitamin E that occurs during hay storage. Many commercial feeds account for this loss and formulate their feeds accordingly. Some feeds use natural vitamin E, but many use synthetic versions, which is not as bio-available as natural vitamin E. Additionally synthetic vitamin E is not as efficient at raising blood serum vitamin E levels as the natural variety. Synthetic vitamin E is still a good option as it is often cheaper to buy and easier to find than natural vitamin E. Vitamin E supplements can be found in combination with other vitamins and minerals or alone in liquid and powder forms that can be added to feeds. The amount of vitamin E your horse needs will depend on their age, workload, and whether they are being used for breeding or not. An equine nutritionist can help you determine the right amount your horse needs. 

Reference

1 National Research Council. (2009). Nutrient Requirements of Horses. Sixth revised ed.