Hoof Nutrition Intelligence is a twice-a-month web segment that is designed to add to the education of footcare professionals when it comes to effectively feeding the hoof. The goal of this web-exclusive feature is to zero in on specific areas of hoof nutrition and avoid broad-based articles that simply look at the overall equine feeding situation.
Below you will find Part 1 of the latest question and answer installment that you can share with your footcare clients.
Q: What can you tell me about the role of Vitamin C in the equine diet?
By Eleanor Kellon, VMD
Vitamin C (ascorbic acid) comes in and out of equine supplement headlines. As with many nutrients, exaggerated claims end up being made and when these eventually prove to be unwarranted, the pendulum swings too far in the other direction.
There is no question that vitamin C plays a pivotal role in equine health. While the horse’s body can manufacture vitamin C, fresh grass is a rich source and blood levels drop off in the winter when the horse is on hay.
Just about everyone thinks of vitamin C in terms of the immune system and resistance to infections and “colds.” It actually protects the immune system and other tissues from free radicals that are generated when the immune system cells are activated. As a result, it ends up moderating friendly fire from immune system activity rather than actually preventing infection. Another antioxidant function is the regeneration of “used” vitamin E back into an active form.
Vitamin C is also an important antioxidant found in muscle cells and all body tissues. High levels of free radicals are generated by exercise and exposure to pollutants. Horses with chronic lung disease have been documented to have low levels of vitamin C in lung fluid. Supplementation has been shown to support normal lung function.
In addition, vitamin C promotes the creation of normal connective tissues throughout the body. This includes the integrity of blood vessels, structural framework of bone, joint cartilage, ligament and tendons. It also helps with the restoration of wounds and injuries.
Most mammals, including horses, can manufacture vitamin C from glucose in their livers. But unlike other water-soluble vitamins, there can be a limited storage of vitamin C in the body. Yet we don’t know much about the production and storage of vitamin C in horses.
While their bodies don’t manufacture enough vitamin C to undergo full blown deficiency (scurvy), we don’t know whether they can store the vitamin, whether production decreases with age or how much they can ramp up production in times of increased need, such as with an injury or infection. This uncertainty, along with the observation that blood levels drop in stabled horses and during the winter months, suggests some supplementation may be optimal.
Vitamin C has a low toxicity, with the major issue being gastrointestinal irritation and diarrhea at high doses (typically 20 grams/day or more). Caution should be used in insulin-resistant horses or other horses known or suspected to be iron overloaded. Vitamin C increases the bioavailability of inorganic iron by changing its electrical charge and directly stimulating absorption. A daily dosage of 4.5 grams or less is best and has been shown to increase blood levels of vitamin C over time.
Supplementation is reasonable in horses with chronic lung irritation, musculoskeletal issues, infections or wounds to support the body's inherent antioxidant defenses and maintain vitamin C supplies for normal functions under conditions of high demand.
Vitamin C may be supplemented alone or in combination with plant and/or nutritional antioxidant ingredients such as bioflavonoids, grape seed and skin, vitamin E, berries, glutamine and N-acetyl-cysteine.
Dr. Eleanor Kellon, a staff veterinary specialist for Uckele Health & Nutrition, has been an established authority in the field of equine nutrition for over 30 years. The owner of Equine Nutritional Solutions in Robesonia, Pa., she is a founding member and leader of the Equine Cushings and Insulin Resistance (ECIR) group, whose mission is to improve the welfare of horses with metabolic disorders via integration of research and real-life clinical experience. Prevention of laminitis is the ultimate goal.
Hoof Nutrition Intelligence is brought to you by W.F. Young Co. (Absorbine). 
Like many significant achievements, Absorbine® grew out of humble beginnings—and through the tenacity of someone willing to question the status quo. In this case, it was a young woman in late 19th-century Massachusetts: Mary Ida Young. Her husband, Wilbur Fenelon Young, was an enterprising piano deliveryman who relied on the couple’s team of horses to make deliveries throughout the Northeast. Inspired by Mary Ida and Wilbur’s vision, Absorbine® has continued to add innovative products throughout the years — products used every day by horse owners around the world. Which is why, since 1892, we’ve been The Horse World’s Most Trusted Name®.
Click here to read Part 2 of the April 1, 2018 installment: How do I make sure my horses are being fed to encourage hoof growth and quality?
Click here to read more installments of Hoof Nutrition Intelligence.