By DAPHNE THORNTON
Horses are well suited to most reasonable weather conditions, including cold, heat, wet, and dry. It's the extremes that can cause problems for the kept horse.
Cold Weather
The Horse's Body
In the wild, horses can cope with some of the most extreme cold conditions. They use the natural topography (hills, valleys, etc.) and landscape (trees, brush) to mitigate the effects of wind, rain, and snow. In addition, they grow thick hair coats in winter that keep them warm and mostly dry, even in rain and snow.
But, as soon as we put them in a pasture and limit their access to topography and landscape, we begin to limit their ability to cope.
Horses on flat land without the ability to shelter at will from rain and wind CAN get too cold, or too wet, and can suffer problems related to both. We can intervene with shelters, blankets, or stabling when needed.
In cold weather, riders constantly battle between needing the horse to be cooler when riding – and needing the horse to be warmer when turned out. If our horse is stabled, clipping is one answer to winter riding and showing.
If you plan on showing quite a bit, a full body clip can work for a stabled horse, with plenty of blankets and limited turnout in cold or wet weather. If you don't plan on showing a ton, but want your horse to cool off quicker after a winter workout, a trace clip can help.
With a trace clip, you clip the parts of the body where large veins are close to the surface to aid in a quicker cool down. These are also areas that usually sweat more on horses. You absolutely SHOULD NOT put a horse up or out in cold weather if it is at all sweaty. Sweat is the horse's way of COOLING it's body – and if it's cold outside, sweat will continue to cool the body when heat is what's needed. Also the exposed areas in trace clips make it harder for your horse to retain heat when they need it, so plan on blanketing and stabling when it's really cold or wet.
In addition to all of that, making sure your horse drinks enough water during really cold weather is VERY important. They can get an impaction colic if they don't drink enough. Clean your buckets an extra time to make sure the water is really palatable. We often add flavored electrolytes or peppermints to our horse's water on really cold days to encourage them to drink more.
The Horse's Lungs
Here is the real kicker when deciding if it's too cold to ride. While a horse's body is pretty suited to handling cold weather, their lungs are not. Breathing cold air rapidly and/or deeply can be a significant stress to the airways. Exposure of lower airways to colder air also changes the immune responses of horses for at least 48 hours, causing an "upregulation of inflammatory cytokines and an influx of neutrophils, a type of white blood cells." (Yates)
What this means to us is that if a horse is just standing around (i.e. not breathing rapidly or deeply), their longer airways allow the air to be warmed and humidified before it reaches the lungs. If a horse is exercising (working), the air reaches the lungs more quickly, and is colder and drier.
Very few studies have been done on the effect on horses of breathing cold air. The one most cited is from Oklahoma State University, and the temperature used was 4° C (39° F). Specifically, researchers found evidence of lung inflammation in healthy, fit horses that were exercised in those temperatures. They also found that horses housed in the same temperatures but not exercised did not show any inflammatory changes.
So, we generally use around 25° or lower as our cutoff for lessons (exercising). The study horses were galloped for 15 minutes, and we don't gallop. However, we w/t/c and jump for 30 minutes, so we know we need to be mindful of asking for exercise in cold weather.
Hot Weather
Horses are not particularly suited to hot, humid weather conditions – like we often have during Midwest summers. They are the only mammal, besides humans, that cool their bodies by sweating. Humidity limits the evaporative effect of sweating – and it is evaporation of sweat that provides cooling.
Horses do much better in hot, dry climates. That's why there are native desert and high plains breeds, but no native jungle breeds. Early horses adapted to living in forested land, but modern horses are primarily grassland creatures.
Also, horses produce large amounts of body heat during chewing, digesting and metabolizing feed, so avoid riding them too close to feeding time during hot weather. Heat generated during food digestion added to the heat generated by exercise could push them into heat stress.
Symptoms of heat stress include:
Profuse sweating or less sweat than expected.
Hot skin (might progress to cold if skin circulation shuts down).
Muscle weakness.
Stumbling.
Rapid breathing. (Normal breathing rate for an adult horse is 8-18 breaths per minute.)
Rapid heart and pulse rates that don't recover after exercise.
Increased body temperature of 102 degrees to 106 degrees F. (Normal temperature is 98-101.5
degrees F.)
Signs of dehydration, including loss of skin elasticity, sunken eyes, tacky membranes and
cessation of urination.
HEAT STRESS IS SERIOUS IN HORSES!
As a general rule, if the air temperature PLUS the relative humidity total less than 130, the horse's cooling systems will work well. They can sweat, and expire heat through the lungs. When those totals go over 130, cooling efficiency decreases. We can still ride, but need to be cautious and make sure our horses don't overheat.
When the totals climb to over 150, we really start to see horses experience difficulty cooling off. You can also use the NOAA Heat Index tables as a guide to when it's too hot to ride. Generally for us, a heat index of 100 indicates using an abundance of caution, and a heat index of 105 is a no-go unless you are riding very early in the morning or very late in the evening. Anything higher than that, and we are definitely canceling.
Ways to manage heat and stabled horses include using fans (we do) and making sure they have adequate water. We bring horses in early on really hot days so they are not out in the hottest part of the day. We fill water buckets 3X a day during summer. And we don't exercise our horses if the temps are dangerous.
Pastured horses need access to shade and plenty of clean water. They should NEVER be ridden to a sweat and then just turned out. Cool them out well (including hosing with lukewarm to lukecool water) and make sure their heart and respiration rates have returned to normal before sending them back out to pasture.
During particularly bad heat spells, oral electrolytes can benefit both stabled and pasture horses. They can be fed in grain or added to water buckets (for stabled horses). They are also available in paste form.
