Horse blankets and hair growth

Researchers found that blanketing has little or no effect on horse hair growth over time.

By now you’ve put away your blankets for the season, but a study from the University of Wisconsin, River Falls, may have you rethinking how you will use them when the cold weather returns this year. Researchers found that blanketing has little or no effect on equine hair growth over time.

Research shows that blanketing has little or no effect on a horse’s hair growth. (Adobe Stock)

The study

For the study, eight mature horses were blanketed starting in late October and eight were left uncovered all winter long. None of the horses were clipped. Between October and the following March, researchers took 20 hair samples from the hindquarters and non-mane side of the neck of each horse every month. They then measured and averaged the length and diameter of each hair.

The data showed that blanketed horses had slightly shorter neck hairs in January and February than did unblanketed horses—a difference of 15 and 12 millimeters respectively (less than 3/5ths of an inch in each case). However there was no difference in hair diameter between the two groups.

 “This study does show there was a difference in hair coat length. But this was only statistically significant for neck hair two months out of the year,” says Michelle DeBoer, PhD. “So this research shows that you can reduce hair coat with a blanket, but it may be a short-lived change.”  

DeBoer adds that starting blanketing earlier may have changed the data. “Blankets were applied at the very end of October when temperatures consistently fell below 40 degrees Fahrenheit. If blankets were to be applied sooner, a greater difference likely would’ve been observed.”

Practical implications

While blanketing clipped, elderly and otherwise vulnerable horses may be a necessity, owners are wise to consider all the implications before deciding to blanket a horse who can keep warm without a blanket.

“I know some people blanket to decrease hair length or improve cleanliness,” says DeBoer. “While that may have some benefits, I think people need to be aware of cost associated with blanketing, and not just financially, but the time—you need to make sure they fit correctly and buckles/straps are the right length with snaps facing the right way. Blankets should be checked regularly for wetness or tears.”

Plus, she adds, it’s important to check under blankets regularly for rubs or changes in body condition. Additionally, “blanket weight should be changed according to weather to prevent horses from overheating, which can be time consuming, especially if you don’t live on site with your horses,” says DeBoer. “So while there may be benefits, you need to make sure you uphold your end of the deal in blanketing properly and safely.”

Another factor

An alternative—and likely more effective—strategy for minimizing coat growth during winter is controlling the horse’s exposure to light. “Photoperiod, or amount of daylight, is the main variable that impacts horse hair coat,” says DeBoer. “Using masks that are often used [to encourage brood mares to cycle]. Having lights in your barn on for an extended period of time can help.”

Reference: “Changes in hair coat length and diameter in blanketed and nonblanketed adult horses in the winter,” Journal of Equine Veterinary Science, January 2023

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