California Riding Magazine • March, 2014

Ask the Vet

by Lydia F. Gray, DVM, MA

Question: I live in Kentucky where slushy winter storms are very popular. I just got a new mare who has a thinner winter coat than the rest of my horses do, and when I went to the barn to feed this morning, she was shivering. I normally do not blanket my horses, and they usually have 24 hour access to pasture. I don't have a run-in shed for them, but when it gets really bad out, I usually open the gate that lets them into our barn so they can get under it and out of the bad weather. I was wondering if what the possibility is of my mare getting sick and what I should do. Thanks for your time and your advice, I really appreciate it. KH, Kentucky

Dear KH,
You've caught me in the middle of holiday shopping at SmartPak, taking advantage of their incredible deals to get my horse a new heavyweight blanket for this winter. He's become, err, too "big-boned" for his old one. That said, I agree with you that, in general, most horses do quite well at keeping warm simply when they are able to get out of the wind and rain.

According to NRC Nutrient Requirements for Horses, the "thermoneutral zone" for horses, or, the range of lower and upper temperatures in which the horse is capable of maintaining its body temperature with little or no energy expenditure, has been reported to be as low as 5°F and as high as 77°F. Now, these aren't hard and fast numbers, as many other variables can factor in such as individual horse variation, whether wind and precipitation/humidity are also present, and what temperatures the horse is acclimatized to. But these values give you a good idea of the range of temperatures that horses can handle on their own.

In your case, it sounds like you have a mare that isn't used to the weather yet where she is located now and might need some outside assistance in maintaining her core temperature. A turnout blanket with some fill (medium or heavy) is a good choice since it will also repel water. And if your herd tends to be on the rowdy side, get one made of high denier or with rip-stop technology to help avoid those "friendly" tears. Just make sure that someone checks the blankets daily, because torn apparel or loose straps can be dangerous, while dramatic temperature changes or a soaked garment make things worse than not wearing anything at all. Another factoid from the NRC: heat loss during cold exposure can be reduced 9% by shelter alone, 18% by blankets, and 26% by shelter AND blankets.

That really is the main reason for providing shelter and blankets to horses in the winter: to avoid heat loss which requires energy expenditure (ie shivering). We're not really worried that horses are going to "catch a cold" or come down with the flu if they get chilled; we're concerned that using energy to keep themselves warm is going to cause weight loss. Therefore one way to make sure horses have plenty of energy to maintain their weight and their core temperature is to feed more hay in the winter. Not only will this add calories or energy to the diet, the process of fiber fermentation in the hind gut generates heat and literally warms the horse from the inside out.

The winter "Trio of Temperature Control" then is shelter, blankets, and hay. Provide your horses, especially your mare, with these three advantages during cold months and trust me, they will thank you!

Article provided by SmartPak.
Dr. Lydia Gray is the Medical Director/Staff Veterinarian for SmartPak, where she guides research and new product development, answers questions on her Ask the Vet blog, and speaks around the country at various events such as Equine Affaire, Dressage at Devon, and the USHJA Trainers’ Symposiums.