Some horse owners rug their horses all year round, and others don’t bother at all, believing that the horse’s natural ability to self-regulate their own temperature and some shelter from the worst of the weather is all they need. According to Equiculture , horses should be rugged when:
In Australia, temperatures can get pretty high in summer and when they exceed 25 degrees, horses can experience thermal stress . As mentioned above, horses must have access to appropriate shelter that will protect them from extreme weather conditions such as excessive rain and wind or high levels of heat. However, access to shade is not always possible in rural Australia and so it has been suggested that rugging them with a light cotton rug is an effective alternative .
Barbara Padalino and associates  conducted a recent study (2019) to determine the effects of a light-coloured cotton rug on a horse’s thermoregulation abilities and stress levels. They studied the rug’s effects on the horses’ heart rate, rectal temperature, respiratory rate, sweat production, and stress-related behaviours (tail swishing, licking and chewing, pawing the ground, self-care, and repeated head movements) . They found that the rectal temperature and sweat production was significantly lower in the horses who did not have a rug on compared to those who were rugged . However, they also found that rugged horses showed significantly less stress-related behaviours than those who were not rugged, suggesting that the rug was effective at minimising the horse’s annoyance caused by flying insects . So, while wearing a light cotton rug in summer helped to prevent the annoyance caused by flying insects, it didn’t help the horse thermoregulate which could lead to more serious problems in the future. Therefore, this study recommends that appropriate shelter from the sun is a more effective form of protection .
Hypersensitivity to insect bites is common in a lot of horses, particularly in the summer months . Horse’s that are susceptible to the irritation are allergic to the insect’s saliva, rather than the bite itself . The condition can cause the horse to become itchy, form hives, and can result in hair loss . Wearing a cotton rug and fly mask is an effective method of preventing the insects from reaching the horse’s skin, though as we now know, wearing a rug – even a light-coloured cotton one – can cause heat stress and the loss of electrolytes in horses. Therefore, horse owners need to weigh up the advantages and disadvantages of the rug and draw their own conclusions.
Winter is the most common time for horse owners to throw a rug or two on their horses. Whether it is to help keep them warm in the chilly temperatures, to prevent mud monsters from forming, or both.
Carolyn Hammer & Mattia Gunkelman  conducted a recent study (2020) to examine the difference in the surface temperatures of horses during cold weather when they have no rug, light weight (0g), medium weight (200g) and heavy weight (400g) rugs on. The horses were sent out into the cold (temperature -23 degrees and wind chill -32 degrees) where they had unlimited access to hay and water . After 1 hour they were brought back in and their temperature over the lumbar area was recorded . It was found that the temperature was warmer on horses with a heavy weight and medium weight rug than those with a light weight rug or no rug at all, though those with a light weight rug were slightly warmer than those with no rug . Therefore, rugs are an effective method of keeping your horse warm during winter.
However, it has never gotten as cold as -23 degrees in Australia (thank goodness!) and we can have some warm winter days. This can make it difficult when trying to decide whether to rug. Thankfully, Cecilie Mejdell and associates  from Norway have found a way to get horses to tell them whether they would like a rug on. They conducted a study in 2019 in which they used operant conditioning to train horses to communicate using visual symbols to inform the handler whether they would like a rug on or not . By day 14 of their training, all the horses in the study understood what the visual symbols meant and when the horses were tested under different weather conditions the results found that the horse’s decision was not random but based on the weather . Therefore, the horses were found to not only understand the consequences of their choice but also that they were able to successfully communicate their preference . So, if you’re ever stuck wondering whether you should throw a rug on your horse or not, all you must do is ask!
 Myers, J 2021, Is it essential to rug a horse? Yes/No/Maybe…, Equiculture, viewed 24/09/2021, <https://www.equiculture.net/blog/Is-it-ESSENTIAL-to-rug-a-horse>
 Padalino, B, Loy, J, Hawson, L & Randle, H 2019, ‘Effects of a light coloured cotton rug use on horse thermoregulation and behaviour indicators of stress’, Journal of Veterinary Behaviour, vol. 29, pp. 134 – 139
 Kentucky Equine Research Staff, 2013, Insect Bite Hypersensitivity in Horses, EquiNews, viewed 24/09/2021, <https://ker.com/equinews/insect-bite-hypersensitivity/
 Hammer, C & Gunkelman, M, 2020, ‘Effect of different blanket weights on surface temperature of horses in cold climates’, Journal of Equine Veterinary Science, vol. 85, pp. 1 – 3
 Mejdell, C.M, Buvik, T, Jørgensen, G.H.M & Bøe, K.E 2016, ‘Horses can learn to use symbols to communicate their preferences’, Applied Animal Behaviour Science, vol. 184, pp. 66 – 73