Summer has finally started, and it became hot and very humid very fast (at least in Finland). Our horses can have difficulties adapting to the new conditions, as they tend to cope better with a colder climate than with hot and humid weather. The ideal temperature range for horses, the thermoneutral zone, is between 5 – 25 °C. Additionally, horses have a relatively small surface area in relation to their body mass, which makes thermoregulation a challenge especially in hot and humid conditions.
Horses can adapt to warmer temperatures, but they are susceptible to heat stress. There is not a clear definition of heat stress in horses, but it includes the inability to maintain body temperature in a healthy range. If heat stress is ignored for too long, it may develop into exertional heat illness (EHI), which can at worst cause brain damage or even be fatal.
Horses regulate their body temperature by thermal radiation, conduction, convection, and/or evaporation. If these mechanisms aren’t enough to cool the horse down to avoid heat-induced damage, there are ways we can help them to cool down. The most common way surely is hosing the horses off after training or after pasture time, for example. Some prefer to use cold water, some prefer lukewarm. Some always start at the right hind leg not to stress the heart, and some always start at the left front leg to cool the blood circulation quicker. Others swear on scraping the horses off after washing, while others prefer to leave the horses wet.
Is there a right way to cool the horses down?
What does science say?
Summer weather can be hard on horses. © Michelle Lüscher
A study done in 2020 compared five different cooling methods in hot and humid environments on Thoroughbred Horses. They compared walking the horses with no additional cooling, walking the horses with fans producing an air current of 3.0 m/s, walking the horses with the intermittent application of cold water (10°C) either with scraping or without scraping, and keeping the horses stationary, with the continuous tap water (26°C) application via shower hoses.
All the cooling methods resulted in lower rectal temperatures after 30 minutes than only walking the horses after training. Showering the horses with tap water cooled the horses down the fastest. Even though hosing the horses down cools them the quickest, there should still absolutely be a cool-down-phase consisting of a light trot and walk after training as well to keep the body healthy and help recover from the exercise.
Whether it is beneficial to scrape off the water during cooling remains controversial. There are no studies that prove that scraping the horses off cools them down quicker. On the other hand, scraping doesn’t seem to be harmful either, so it might just be a personal preference. Personally, I find it also important to read our horses when it comes to water temperature. There is no need to hose them down with cold water. So, if they are unhappy with cold water and they prefer lukewarm water just use lukewarm water and keep them happy.
In addition to the cool-down-phase in training and hosing the horses off after training, there are other things we should also do to help our horses with the heat. Take off boots and bandages as soon as you are finished with exercise. It might be good to ask yourself if you even need to use thick boots or bandages, as the heat accumulation under protective gear can cause tissue damage in the horse’s legs. Sometimes it can be beneficial to untack the horse for the cooling-down-phase completely.
Also, remember to give horses enough clean and fresh water, which is not too cold. You can use mash, for example, to make the water taste better and encourage the horse to drink better. Also make sure that water runs in automatic water troughs at least at a current of 8l /min. It is important to make sure that the horse is not out of breath when offering something to drink.
Having a salt block in the box and/or pasture is important all year round. It is not enough though, and horses probably need to get additional salt or electrolytes in their feed at least in the summer months, maybe even in the winter too. Especially if horses work and sweat a lot, they should get some complementary salt or electrolytes in their daily ratio. This helps them to maintain and regulate normal functions in the body. Ask your equine feeding specialist for help, if you have questions regarding equine nutrition.
References
Kang, H., Zsoldos, R. R., Sole-Guitart, A., Narayan, E., Cawdell-Smith, A. J., & Gaughan, J. B. (2023). Heat stress in horses: a literature review. International journal of biometeorology, 67(6), 957–973. https://doi.org/10.1007/s00484-023-02467-7
Kang, O., Ryu, Y., Yun, Y., Kang, M. (2012). Effects of cooldown methods and durations on equine physiological traits following high-intensity exercise. Livestock Science, 143(1), 70-76. https://doi.org/10.1016/j.livsci.2011.08.016
Takahashi Y, Ohmura H, Mukai K, Shiose T, Takahashi T. (2020). A Comparison of five cooling methods in hot and humid environments in Thoroughbred horses. J Equine Vet. 2020;91:103130–103130. https://doi.org/10.1016/j.jevs.2020.103130
