It is the beginning of Summer and today is hot! I have a feeling this Summer is going to be a scorcher, so along with the ongoing drought and threat of bushfires, dealing with extreme heat is going to be another concern for horse owners. Prolonged exposure to high temperatures can result in heat stress, heat stroke and issues such as dehydration, colic and muscle spasms.
To help avoid the above issues here a few management strategies to consider. Obviously, horses must have access to adequate shade to provide relief from the sun and if your horse is stabled fans and mist are a great way to help keep them cool. You should also slow down the work and ride in the cooler parts of the day, making sure you remove tack as soon as you’re done and hose down with water. Clipping horses that have a long hairy coat is also a great help to keep them cool. Along with these tips, the following is what you can do nutritionally to help your horse through the heat of summer.
Provide unlimited access to fresh, clean, palatable water. This one is absolutely crucial as water is the number one absolute most essential nutrient. With hard exercise and hot weather horses can drink around 10-15 litres/100kg of bodyweight daily (that’s around 75 L for a 500kg horse). If your dam/creek has run dry like mine this will mean that troughs and buckets have to be constantly filled and cleaned. When my horse is stabled, I make sure that I have a few large buckets filled, this is especially important on hot days and if you have a horse like mine that loves to play with anything and everything.
There is also nothing worse than going to an event and finding out that your horse won’t drink (I also have one of these fussy fellows who doesn’t like drinking when he’s away from home and it’s so frustrating). If you have a horse that goes off water while away there are a few things you can do to encourage them to drink such as taking your own water from home, adding flavouring to the water (apple juice, cordial, molasses – find out what flavour your horse prefers), adding a bit of grain/apples/carrots to the water or adding electrolytes. Remember you need to determine what works for your horse at home prior to leaving and if you are adding anything to the water then it will have to be cleaned even more regularly. I also recommend that you provide a second water bucket without anything added to it.
Another way I increase my horse’s water intake on a daily basis is by providing a diet high in fibre as fibre loves to hold water. Using ingredients like copra meal, soy hulls and sugar beet pulp that swell up when they are soaked is a great way to provide a small internal reservoir of water for the horse to draw on when it is needed. Add any supplements to the soaked feed just prior to feeding and don’t leave to soak for long periods, especially in hot temperatures where they can quickly spoil.
This brings me to salt. When it is hot horses need to sweat to prevent their bodies from dangerously overheating. Water and electrolytes including sodium, chloride, potassium, magnesium and calcium are all lost from the body through sweat. For effective sweating to occur a horse needs to be well hydrated and have a good supply of electrolytes in its body. Salt (NaCl) is composed of sodium and chloride and they are the most commonly deficient electrolytes in a horse’s diet. Very few forages contain enough sodium to sufficiently meet maintenance requirements so when I recommend a good quality vitamin and mineral supplement (MegaMin Equine Enhancer) to balance shortfalls in the pasture. I also recommend that free choice plain salt is also provided as horses will actively seek salt when they need it. I prefer loose salt to a salt block as it is cheaper, plus it is difficult for a horse to lick enough of a hard block to fill high requirements. I do use a commercial electrolyte supplement when my horse is away from home at a competition and working a lot harder, longer and sweating more than usual. According to Richards (2019), “a well-formulated electrolyte supplement will contain 43-48% chloride, 20-25% sodium, 10-12% potassium and smaller amounts (usually 1-2%) of calcium and magnesium. They also shouldn’t be filled with glucose or other fillers”.
Watch for horses that don’t sweat, as your horse could be suffering from a serious condition called Anhydrosis. Horses rely on being able to sweat to cool themselves down and if they don’t have the ability to sweat, they find it very difficult to stay cool. You might notice these horses “puffing” as they resort to offloading heat via their lungs by breathing faster and harder. These horses are at serious risk of hyperthermia (signs of heat stroke below) and veterinary advice should be sought.
Try to avoid diets that contain very excessive levels of protein as during the process of digestion and metabolism of protein a lot of heat is generated. However, keep in mind that during drought conditions when forage quality is poor there is often a significant protein deficiency, so it is important that protein, particularly essential amino acid requirements are being met.
Now I usually recommend that horses have a diet that is high in forage but when the fibre is fermented in the hindgut a lot of heat is produced which in turn increases the amount of heat that the horse needs to get rid of to keep its body temperature normal. So, for horses that are in significant work in hotter climates then a lower forage diet may be warranted. However, it is still essential that horses receive a minimum of 1.5% of their bodyweight in forage daily. Adding oil (the best option as it produces the least heat) or cooked grain to the diet will help meet the horse’s energy requirements but remember not to feed raw grain as this will once again lead to a lot of fermentation and heat production in the hindgut.
Make sure you are aware of the signs of heat stress (Martinson, 2018):
- Rectal temperature above 39°C
- Increased breathing rate
- Increased heart rate
- Profuse sweating
- Droopy ears
- Reduced feed intake
- A skin tent lasting several seconds after pinching the skin of the neck or shoulders
Heat stroke is an emergency and is a serious overheating condition in horses, which may occur from being worked hard in extreme heat and/or humidity. Signs of heat stroke include include (Martinson, 2018):
- Rectal temperature above 41°C
- Rapid heart (more than 60 beats/min) and breath rates (more than 40) that don’t decline within 20 minutes of stopping exercise
- Dehydration with dry mucous membranes and prolonged skin tents of 4-10 seconds
- Distress (whinnying)
- Muscle weakness
If you suspect your horse is suffering from heat stroke contact your veterinarian immediately and get your horse into a cooler environment.