Q. My horse is turned out to pasture for at least part of each day. Every winter he gets scratches. Is there anything I can do nutritionally that might help prevent them?

—Via e-mail

A. Most of the time scratches aren’t too big of an issue. However, they can indeed become a big problem literally overnight. I personally had a mare who went from having a couple of tiny spots of scratches one evening to being nonweight-bearing lame and having full-on cellulitis in the leg the next morning. My advice is twofold: don’t ignore scratches if present, and prevention is ideal.

What is Scratches?

Scratches—sometimes referred to as grease heel, mud fever, or equine pastern dermatitis—is a skin infection on the back of the pastern and heel; sometimes scabs can extend as far as the fetlock area. The location can make it hard to find, especially if a horse has a lot of hair or feathers. While scratches is common in breeds that have a lot of fetlock hair, such as drafts, it can occur in horses of any breed, and some horses seem more prone to developing scratches than others.

Wet, muddy conditions and or skin trauma in the area tend to be predisposing conditions. Some of the worst scratches I have ever seen were the result of an owner washing her horse’s legs daily when brought in from pasture to remove the mud from his hooves and legs. Wet conditions reduce skin’s integrity and wet-and-dry cycles can lead to skin chapping and cracking. Occasionally, insult from an insect bites or some kind of wound on the skin is all that it takes for scratches to develop.

With a break in the skin, bacteria such as Staphylococcus aureus and Dermatophilus congolensis are free to enter, causing an often-painful infection that secretes a greasy serum exudate (hence the name grease heel). This accumulates on and mats the hair in the area creating what appears to be a hard scab. Single scabs vary in size, but the ones I have dealt with have been about pea-size. In more severe infections clusters of scabs can develop as the area becomes ulcerated and swollen. The area can be very sensitive, and the horse can become lame.

Treating Scratches

You should reach out to your veterinarian not only to determine the best topical or systemic treatment but also to accurately determine the cause of the scratches. In some cases, lesions can actually be the result of an infectious zoonotic condition, parasite infection, or a reaction to ultraviolet light.

Basic treatment, which can be lengthy depending on how badly the horse is affected, typically includes clipping the area so moisture isn’t trapped against the skin and keeping the affected area dry. Barrier creams might be beneficial and, in more several cases, your veterinarian might prescribe topical or oral antibiotics. As often as possible affected horses need to be kept in dry conditions.

Preventing Scratches in Horses

Clearly it would be much easier to avoid scratches in the first place. As for whether nutrition can help, there are certainly steps you can take to help improve skin’s resilience. The first step is to make sure the horse’s diet meets all his nutrient requirements and trace mineral needs.

Zinc, a trace mineral often lacking in forage-based diets, has been shown to stabilize cell membranes, and metalloenzymes (enzymes containing a metal as an integral part of its active structure) such as metallothionien rely on zinc as an essential cofactor. Metallothionien stimulates basal keratinocytes, which help give skin strength and flexibility. One keratinocyte functions is to help maintain the tight junctions between the nerves and skin.

Kerotinocytes also play a role in immune function. Skin is the body’s first line of immune defense and, as such, it needs to be continuous without breaks that could allow pathogens to enter. Kerotinoctyes create a barrier and help to maintain the skin’s moisture which helps skin to stay pliable and less likely to crack. Therefore, if a horse’s diet is zinc-deficient, he might not have optimal basal keratinocytes stimulation, tissue healing abilities could be reduced, and an effective barrier might not be maintained.

Developing the Diet

Select a high-quality commercial feed, and feed it at the manufacturer’s recommended daily serving. This could be a ration balancer or performance feed depending on your horse’s job and body weight. Either product fed correctly should provide adequate zinc as well as other key trace minerals such as copper.

Providing a source of fatty acids in the diet could also help as they reduce dry skin and dry skin is more likely to crack. Good sources of fatty acids include plant sources high in omega-3s, such as flax, camelina, or chia.

If making these changes/additions does not have the impact you’re seeking, consider working with a nutritionist who can evaluate the diet more closely. Other dietary mineral sources, such as the water or forage, could be negatively impacting zinc and other trace mineral absorption. If this is the case, a qualified equine nutritionist should be able to suggest some adjustments to the diet that take this in to account.