Many studies have now been done on the so-called "blanketing" (putting the blanket) of horses .. there is still a lot to investigate but some studies can already reveal interesting results.
It has become routine (and a bit fashionable) to put blankets on horses all year round. Nowadays the most disparate types are on the market, from the light raincoat, to the mid-season, to the anti-fly blanket etc. So far there have been very few studies on the effect of blankets on the horse's natural thermoregulation.
Like humans, horses have a "thermoneutral zone," an optimal temperature range within which they can comfortably maintain their body temperature. For adult horses in mild climates, this range is 4 ° C-25 ° C. On the other hand, humans have a thermoneutral temperature range (when naked) between 25 ° C-30 ° C. This means that when humans already feel cold, horses are still fully in the comfort zone. We always talk about not clipped (full coat) horses. According to the human perception of cold, there is always a tendency to cover the horse, sometimes when it is not necessary.
A study by Kim Hodgess, a student of Duchy College in the United Kingdom, was presented in which they try to understand how the use of various types of blankets changes the horse's temperature (raising it) and how this can affect its well-being. The study was presented at the ISES (International Society of Equitation Science) conference in Rome (Sept. 2018). The research team studied horses that, from routine stable management, were regularly covered, 10 indoors and 2 in pasture. 3 horses under examination wore light, non-waterproof blankets, usually used to protect the horse from insect bites; these blankets cover most of the horse's body including the neck and belly. 6 wore fleece blankets, 2 wore light quilted blankets and, finally, 2 horses (of "control") were without blankets (one in the box and one in the paddock).
The body temperature of each horse was measured by recording the data directly on the body of each animal. The ambient temperature was also measured and checked every minute for 24 hours with recorders connected to the door of the stable or on the wooden boards of the paddock. The results showed important and significant differences in temperature in the horses wearing the different blankets: the horses wearing the light blankets had an average temperature increase of 4.2 ° C; those who wore fleece blankets 11.2 ° C; those with light quilted blankets 15.8 ° C.
Four healthy, covered horses had body temperatures between 24 ° C-30 ° C, compared to the "control" ones, without blankets, whose body temperature was 12.5 ° -18.5 ° C when the ambient temperature dropped below the "thermoneutral zone" (TNZ) at 4 ° -4.5 ° C.
The conclusions of this study showed how the different types of blankets can have a significant influence on the rise in temperature, beyond the temperatures that are comfortable for the equine, and could therefore compromise its thermal self-regulation capacity. Sure, the use of blankets may be necessary for some horses and in adverse weather conditions, but it is vital to select the correct type. Proper use and application must be seriously considered to avoid negative impact.
In this regard we have found the chart below, which shows us, for clipped horses and full coat, which type of blanket to adopt (if necessary) depending on the range of external temperatures. As you can see, a horse that is not clipped may only need it in an average temperature range below zero (we are talking about medium-aged horses in good health).