Horses get vitamin E from fresh forage (pasture) | Alayne BlickleVitamin E and selenium play essential roles in horses muscular, neurologic, and immune health. Researchers have linked deficiencies in vitamin E to myelopathies (degenerative disorders affecting the spinal cord) and diseases such as equine neuroaxonal dystrophy (eNAD)/equine degenerative myeloencephalopathy (EDM), vitamin E responsive myopathy (VEM), and equine motor neuron disease (EMND). Veterinarians might use injectable vitamin E and selenium combinations to correct deficiencies and support performance, despite possible serious adverse effects such as anaphylaxis and death.To understand prescribing patterns for injectable vitamin E and selenium products, researchers sent a survey to equine practitioners. John Madigan, DVM, Dipl. ACVIM, ACAW, professor emeritus from the University of California, Davis (UC Davis), spearheaded the project after the U.S. show jumper Chromatic BF died at the World Cup Finals in Saudi Arabia in 2024 after administration of an injectable vitamin E-selenium product. Madigan said he felt this was a significant welfare issue and reached out to his UC Davis colleagues who have expertise in vitamin E and selenium use in horses. He and one of those experts, Carrie Finno, DVM, PhD, Dipl. ACVIM, professor of veterinary genetics and the Gregory L. Ferraro Endowed Director of the UC Davis Center for Equine Health, shared the results of the survey at the 2025 American Association of Equine Practitioners Convention, held Dec. 6-10, in Denver, Colorado.They reported that 285 veterinarians completed the survey, 40% of whom were in practice for more than 20 years, showing the high experience level of respondents. Sixty-five percent of veterinarians worked on sport horses, 50% on pleasure horses, and 21% on racehorses. Survey respondents were primarily based in the U.S.Adverse Effects With Injectable Vitamin EHorses need the antioxidants vitamin E and selenium in their diets, but regional differences in forage can lead to variation in nutrient availability. Some horses might not have access to fresh forage (pasture), resulting in some of the disorders mentioned, while others lack selenium, creating different deficiency risks. Despite warnings of fatal anaphylaxis reactions on product labels, the survey showed 52% of respondents reported using injectable vitamin E-selenium products. Forty percent said they used these products three to 10 times per year, and 34% said they used them more than 10 times per year.More than half of respondents reported using vitamin E-selenium injections in horses with suspected deficiencies, which Finno recommended revising. We really need to assess levels and not just assume deficiency, she said.Additionally, 28.7% of surveyed veterinarians used vitamin E-selenium injections for performance support. Racehorses received vitamin E-selenium injections more commonly than other types of horses.Most veterinarians administered the injections intramuscularly (IM, 75%), and 16% administered vitamin E-selenium intravenously (IV). Thirty-one percent of respondents reported adverse events following injections, and 65% of those were anaphylaxis. This is absolutely terrifying to me, so I hope this is terrifying to everyone in this room, said Finno. This is something that we are giving with the best of intentions, and 65% of adverse events are anaphylaxis.Of the other reported adverse events, veterinarians noted swelling/pain at the injection site in 48% of reports, followed by respiratory distress (16%) and diarrhea (6%). Of the anaphylaxis cases, 62% of horses recovered, but 35% of the horses died, Finno said.Risk-Benefit Ratio of Injectable Vitamin E in HorsesDespite the high rate of adverse effects, including risk of anaphylaxis and death, only about one-third of veterinarian respondents discussed those risks with the owners. Another one-third never discussed the risks with clients before using the product, and only about one-third of veterinarians were prepared with risk mitigation protocols.In terms of a risk-benefit ratio, about one-third of veterinarians said they feel the risks outweighed the benefits, but another third felt the risks do not outweigh the benefits. The remaining one-third remained uncertain.This really reflects a lack of consensus in equine practice regarding the use of this product, and we are hoping that this is the start of more discussion about this, said Finno. Sharing this data is at least going to get us aligned that these complications occur, that they are highly concerning, and we need to get on the same page.Future Research and Discussion Directions Key issues Finno encourages further discussion about include:The extremely high rate of anaphylaxis and fatalitiesVariability in practitioner communication about risks associated with injectable vitamin E-selenium productsLimited standardization in safety protocols (e.g., having epinephrine available)I would just argue a vitamin E-selenium injection is just not worth this, Finno said, especially when one considers these commercial products do not include natural vitamin E.The vitamin E is synthetic, which means it is not absorbed well in horses, said Finno. You are therefore just giving selenium. Reserve selenium injections for cases of documented deficiency that potentially do not respond to oral supplementation and be sure to give it intramuscularly, not intravenously. Even if administering selenium IM, have emergency drugs ready, and always discuss risks with owner.Alternatives to Injectable Vitamin EIf a practitioner is looking to increase a horses vitamin E levels, Finno suggested reaching for a well-studied, effective oral product. These products are widely available and very safe, but veterinarians should first confirm the need for supplementation.Pull a baseline blood vitamin E level, said Finno. If a horse has low vitamin E (less than 2 micrograms per milliliter via HPLC testing) and no signs of neuromuscular disease, then offer either a natural liquid vitamin E or natural pellet/powder for two to three months and recheck vitamin E levels. If the horse has signs of neuromuscular disease and is deficient in vitamin E (less than 2 mg/mL) then offer the natural liquid vitamin E for three to five weeks before rechecking blood vitamin E levels.After rechecking, if vitamin E levels fall between 3 and 9 mg/mL, continue treatment and monitor. If the level is 10 mg/mL or more, veterinarians should decrease the dose of vitamin E by 50% and reassess, Finno said. But if blood vitamin E levels drop below 3 mg/mL, increase the dose of vitamin E by 50% and reassess. Finally, if blood vitamin E levels continue to remain low, then perform additional testing for malabsorption.Take-Home MessageVeterinarians use injectable vitamin E-selenium products more commonly than Finno expected, and the practice is far from benign, having a significant fatality rate due to anaphylactic reactions. There are safer alternatives, said Finno. Please stick to those. We need to be advocates for the horses and educate owners and veterinarians about this use of this product.