In the past three or four years, one of the top questions Kelly R. Vineyard, MS, PhD, said she and the other equine nutritionists with Purina Animal Nutrition have been getting from veterinarians is what to do about horses with low serum vitamin E. Why are these horses’ serum E levels low, and what can be done about it? She touched on this topic during a presentation at the 2024 Purina Equine Veterinary Conference, in St. Louis, Missouri.
Understanding Horses’ Vitamin E Requirements
First, stressed Vineyard, if you suspect a horse might benefit from vitamin E supplementation or that a deficiency is causing issues such as muscle atrophy, pull blood to measure baseline levels. This is the only way to know whether your supplementation protocols are effective, she said. Here are the serum α-tocopherol reference ranges for horses:
- > 2 ug/ml: Adequate
- 1.5-2 ug/ml: Marginal
- < 1.5 ug/ml: Deficient
Horses’ vitamin E requirements range from 500-1,000 IU/day, with an upper safe limit of 5,000-10,000 IU/day. This is important to understand, because “things have gotten a bit out of hand, where you’re seeing really high levels of vitamin E supplementation in certain circles—performance horses, especially,” said Vineyard. “Excessive vitamin E will interfere with vitamin A metabolism, impair bone mineralization, can reduce blood clotting, and simply gets expensive to feed at high levels.”
Horses can meet their vitamin E requirements through fresh grass or high-quality, fortified concentrate feeds and ration balancers fed according to body weight and workload, she added. Vitamin E levels in straight grain and hay are much more variable, based on harvest conditions.
Which Horses Need Supplemental Vitamin E?
Horses with certain conditions will need vitamin E supplementation beyond normal daily NRC requirements. These include animals with:
- Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy: 1,000-2,000 IU/day.
- Equine motor neuron disease: 5,000-7,000 IU/day.
- Vitamin E responsive myopathy: 5,000-7,000 IU/day.
- White muscle disease in foals: 2 IU/kilogram of body weight per day for at least three months, paired with injectable selenium.
- Muscle disorders such as PSSM, RER, and MFM: Up to 3,000 IU/day, plus 600 IU/cup of added oil.
- EPM and other neurologic conditions: Up to 3,000 IU/day.
- Low serum values: up to 7,500 IU/day.
Horses that are stressed, exercising heavily, or have no pasture access might also benefit from extra vitamin E, but only if testing indicates low serum levels, Vineyard reiterated.
Vitamin E Supplementation Protocols
If you’re managing a horse with an active medical condition and low serum vitamin E, supplements can be beneficial tools in your dietary toolbox, said Vineyard. These products come in liquid and powder forms.
“The liquid water dispersible form is more bioavailable than the powder,” she explained. “This is natural-source vitamin E with d-α-tocopherol. DL-α-tocopherol is synthetic, which is still usable and absorbable by the horse, but when you’re dealing with a medical condition, go with a natural source.” Studies have shown that natural sources have greater effects on horses’ serum vitamin E levels than synthetic.
Vineyard listed three popular and effective liquid sources:
- Elevate W.S.
- Nano-E
- Emcelle
For long-term supplementation, however, these products can be cost-prohibitive, she said. “For long-term maintenance for these conditions, there are some really good options on the powder side,” she added. These include:
- Platinum vitamin E
- Smartpak vitamin E
- Elevate
When adding vitamin E to a horse’s diet, Vineyard referenced a supplementation protocol flowchart developed by Carrie Finno, DVM, PhD. Basically, you measure the horse’s baseline vitamin E, and depending on the results, give 2,500-5,000 IU/day liquid natural-source vitamin E. Recheck serum levels three weeks later.
“The key when managing these cases with low serum vitamin E is checking and adjusting your supplemental protocol depending on what the bloodwork tells you,” she said. “And that’s going to be affected by the horse’s metabolism.”
The goal is to adjust the diet to bring serum vitamin E levels back up to normal and maintain that long-term using a powder supplement, a good concentrate fortified with vitamin E, and fresh pasture (or at least a good hay).
Related Reading
- Feeding Horses That Can’t or Won’t Eat
- Diet Effects on the Equine Microbiome
- Storage’s Effects on Commercial Equine Grains
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