Frostbite has a low panic level simply because A) it is relatively uncommon for horses,B) it is easily preventable and C) by the time you realize there is a problem it is generally way too late to do much other than deal with the resulting tissue damage.
■ What you see: Initially blanched, very cold areas of skin, ear tips may be swollen.
■ Panic level: Yellow.
■ Causes: Exposure to very cold temperatures.
■ Immediate Action: Thaw the tissue out with warm water. Do NOT rub the tissue.
■Call your vet: The damage is usually done. However, your vet may want to minimize the damage and pain.
■Prevention: Provide dry, windproof shelter during severely cold weather.
Frostbite is caused when cells in tissues freeze. In very cold temperatures your horse will shunt blood flow away from his extremities and concentrate on keeping the core body and the brain warm. In people, this is why your fingertips and toes tend to feel the cold first. In a horse, the most susceptible tissues are the ears. The hooves seem to have some built-in protection against cold —this is not totally understood but may be related to the tough hoof wall covering and the vast network of vasculature in the hoof. A stallion or gelding who suffers from priapism (problems with retracting the penis whether from an illness or post sedation) is also at risk for frostbite there.
Frozen cells rupture as the ice within the cells causes damage to cell membranes. They also put pressure on the blood vessels in the area, disrupting blood flow, which would have kept the area warm and preserved normal cell functions. When the damaged cells thaw, it is usually already too late to save the tissues. Small areas will dry and fall off (dry gangrene). Large damaged areas could lead to bacterial infection and toxin spread.
Horses generally prefer cold temperatures—even down to below zero F. In really cold conditions though, it is important that they have a dry place to shelter out of the wind. A low wind-chill factor on a damp or wet horse can be a recipe for disaster.
Environmental factors like diet could also contribute to frostbite. Feeds contaminated with ergot alkaloids from fescue may cause vasoconstriction, especially of extremities as a consequence of the mycotoxins. Combine the vasoconstriction from this fungus along with wet and very cold temperatures and you have the perfect scenario for frostbite of ears and possibly tails.
If you feel your horse has some frostbite, you need to warm the area gently. A swollen and/or blanched ear needs to be warmed up with warm compresses gently held around the area. Do not rub! This could do more damage to the already compromised tissues. Gentle warming may save some tissues. Any tissue where the cells have actually already frozen will be lost. Generally the tissue will dry, harden and then crack off.
Frostbite involving hooves is even less common than ear tip problems. While rare, this problem is very serious.
A horse who sloughs tissue around the hoof and fetlock may survive, but if the hoof itself is involved, euthanasia is often the only humane choice.
Preventing frostbite is pretty straightforward. Make sure your horse has access to a dry shelter that is out of the wind and wet on really cold days. Provide plenty of good feed so he has calories to burn for body warmth if need be. Do a daily (ideally even twice daily, if you can) check on any horses that are mostly living outdoors in cold weather.
Article by Deb M. Eldredge, DVM.