On Blanketing Horses

Blanketing horses has become a fairly common practice, no matter what the season. Sheets in the summer sun, sheets in the rain, heavier blankets fall through till early spring. One can’t help but wonder, is this based on a real or perceived need for the horse’s well-being or is it a manifestation of the human tendency to anthropomorphize animals? Horses evolved and thrived in a range of climates over hundreds of thousands, nay, millions of years without well-intentioned humans covering them with blankets to protect them from the elements.

Natural adaptations to the cold

This isn’t to say that all horses should immediately have the rugs pulled out from under… er off of them. Blankets can serve a practical purpose, however, they can also have negative welfare implications, interfering with natural behaviours and thermoregulation. Horses have an excellent capacity to tolerate cold temperatures and acclimatize to seasonal conditions (Autio et al., 2006; Cymbaluk, 1994). For example, feral horses can comfortably withstand temperatures as low as -30 to -40°C without experiencing a drop in core body temperature (Ladewidg, 2016; Mejdell & Bøe, 2005). While the ability to withstand sub-zero temperatures will vary amongst breeds and individual animals, most domestic horses are well-equipped for winter.

The most obvious adaptation is the thick winter coat that begins growing in the summer. This is an innate response that correlates to changes in the photoperiod, i.e. the decrease in daylight hours following the summer solstice. The coat keeps the horse warm and dry in wind, sleet, and snow. Additional thermal insulation properties are found in the skin and the highly insulative subcutaneous fat layer. Under normal conditions, horses will gain weight and develop a substantially thicker layer of subcutaneous fat for the winter. Vasoconstriction of superficial blood vessels further reduces heat loss in cold temperatures by redirecting blood flow away from the extremities to the organs (Autio et al., 2006).

Other strategies used by horses to maintain their core body temperature throughout the winter include orienting their bodies to maximize the surface area exposed to the sun to absorb solar radiation, and huddling together to shield themselves from cold wind, with heads facing away from the wind and tails held low and close to the body. Given regular access to food, water, and shelter during winter months, domestic horses generally have no trouble maintaining healthy body conditions and keeping warm, even when temperatures drop well below 0°C (Cymbaluk, 1994; Mejdell & Bøe, 2005; Foster, 2017).

Pros & cons of blankets

The regular use of blankets inhibits hair growth, interferes with the natural insulating properties of the coat (Foster, 2017) and other functions of the thermoregulatory system, and may cause the horse to overheat (Briggs, 2009), so you may actually be doing a disservice to your horse with your well-intentioned actions. When uninhibited by a blanket, the haircoat has increased insulative properties due to the effects of piloerection (bristling of hairs in response to cold), which increases the amount of insulative air in the coat. Piloerection can increase the depth of the haircoat by 16 to 32% (Autio et al., 2006; Cymbaluk, 1994).  Horse hair is also naturally greasy and repels snow, ice, and sleet, providing “a weather shield so complete that horses can stand in a storm until ice forms on their backs without the skin becoming chilled” (Briggs, 2009).

That’s not to say that all horses are better off without blankets. They do serve a purpose and your decision to blanket should take into account a number of factors. Do you live in a wet or dry climate and how cold are your winters? Is your horse at a healthy weight with a good body condition and a healthy haircoat? Is shelter available in the field or paddock? Is your equine pal clipped?

If your horse is clipped, a sheet or lightweight blanket should be used when the temperature falls below 10°C because the natural thermoregulation properties of the coat will be ineffective (Vanden Elzen, 2017; Becksett, 2016). In exceptionally rainy climates, the use of a waterproof sheet on both clipped and unclipped horses may be advisable if your horse can’t readily access shelter in the rain because rain has more of a chilling effect than does snow. When the coat gets wet, its insulating capacity is greatly reduced, which can be exacerbated by wind and cold temperatures, whereas snow does not tend to penetrate a dense winter haircoat due to its drier, granular properties (Autio et al., 2006; Cymbaluk, 1994).

For example, a study of Icelandic horses in Norway found that even with shelter available, the horses spent the majority of their time outdoors in all types of weather. Within the herd of 40 horses studied over the winter period with temperatures reaching a low of -31°C, shivering was only observed on one occasion by a single horse. This was on a rainy day in late autumn when the temperature was +5°C (Mejdell & Bøe, 2005).

Assess your individual horse’s needs

Between now and next fall I encourage you, dear reader, to do some research of your own and re-evaluate what is best for your horse and maybe refrain from dusting off the blankets. Instead, carefully assess your horse’s nutritional requirements and increase access to high quality forage to fulfill its needs for increased caloric intake throughout the winter, along with a steady supply of salt and fresh water. It is also advisable to learn what the lower critical temperature is for the region you live in. Below this temperature, a horse will require an extra two percent of feed for every additional degree the temperature decreases (Cybaluk, 1994; Vanden Elzen, 2017).

For example, in Ontario, the lower critical temperature is -15°C. A 1,000 lb horse requires approximately 20 lbs of forage a day throughout the winter when temperatures are -15°C and above. If the temperature falls to -20°C, the horse must receive an additional 2 lbs of forage. This would be calculated as follows: (2% increase x 5 degrees = 10% increase on 20 lbs, or 2 additional lbs) (Vanden Elzen, 2017).

Rest assured, if your horse is healthy and well-fed, the combined insulative properties of the skin, the subcutaneous fat layer, and the haircoat will adequately keep him warm when the mercury drops.

If you do decide to use a blanket, ensuring a proper fit is important to maximize comfort for your equine friend. The blanket should be removed daily to check for any signs of rubbing which could result in painful lesions from ill-fitting or shifting blankets [3]. Also, keep in mind that being covered is not a natural state for horses. So your horse may appreciate some blanket-free time every day and the freedom to roll and engage in mutual grooming with a friend. These are natural behaviours that are inhibited when a blanket is worn. But that’s a topic for another day.

If you do decide to use a blanket…

I’ll leave you with this blanketing cheat sheet [8] as a general guideline of when and how to blanket your horse. Of note, for an unclipped horse, avoid using a blanket if the temperature is above -6.5°C, otherwise, the horse may overheat and could suffer from heat exhaustion (*Vanden Elzen, 2017).

Temperature

Unclipped

Clipped

Above 50°F (10°C)

No blanket

No blanket or just a light sheet

40 to 50°F (4.5 to 10°C)

No blanket

Sheet or lightweight

30 to 40°F (-1 to 4.5°C)

No blanket, or only a lightweight

Mid to heavyweight

20 to 30°F (-6.5 to -1°C)

No blanket or a light to mid-weight

Heavyweight

10 to 20°F (-12 to -6.5°C)

Mid to heavyweight

Heavyweight plus a sheet or liner

Below 10°F (-12°C)

Heavyweight

Heavyweight plus a sheet or liner or neck cover

References

Autio, E., Neste, R., Airaksinen, S., & Heiskanen, M.L. (2006). “Measuring the Heat Loss in Horses in Different Seasons by Infrared Thermography.” Journal of Applied Animal Welfare Science. 9(3), 211-221.

Beckstett, A. (2016, October 18). “Horse Blanketing FAQs.” The Horse. Retrieved from http://www.thehorse.com/articles/38306/horse-blanketing-faqs

Briggs, K. (2009). “SKIN Deep Your horse’s skin is a huge and complex organ that serves as a barometer for his inner health.” Retrieved from https://ridexc.files.wordpress.com/2011/11/skin-deep.pdf

Cymbaluk, N.F. (1994). “Thermoregulation of horses in cold, winter weather: a review.” Livestock Production Science. 40, 65-71.

Foster, R. (2017, January 26). “Cold Weather and Fresh Horses.” The Horse. Retrieved from http://www.thehorse.com/articles/38711/cold-weather-and-fresh-horses

Ladewig, J. (2016, April 7). “Vancouver 2016 The other 23 hours of the day” [Video file]. Retrieved from https://www.youtube.com/watch?v=SG7lyrDKgYU&feature=youtu.be

Mejdell, C.M. & Bøe, K.E. (2005). “Responses to climatic variables of horses housed outdoors under Nordic winter conditions.” Canadian Journal of Animal Science. 85, 301-308.

Vanden Elzen, L.M. (2017). “Cold Comfort: Domestic Horses and the Long, Cold, Canadian Winter.” Canada’s Equine Guide 2017. p.28-34.

*Vanden Elzen, L.M. (2017). “How to Blanket Based on Need.” Canada’s Equine Guide 2017. p.88-89.

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