Cold is relative to where you live. Riders in Florida may shiver at 50°F, whereas riders in Minnesota might not think twice about tacking when the thermometer reads 0°. Meteorologically speaking, cold weather is generally defined as an air temperature of 40°F or below. Wind, snow, ice or rain will increase the effect of the cold.

Exercising in cold weather affects your horse's body in many ways. Bodily systems react in different ways. Most research on exercising in cold weather has been done on human subjects, but there has been studies on the effects of cold air on equine pulmonary function. Horses are actually used as an animal model for pulmonary research in humans, since the equine pulmonary function is similar to humans. A series of experiments were performed at Oklahoma State University investigating the deleterious effects of strenuous cold weather exercise on airway function in horses. These studies were designed to mimic the conditions that cold weather human athletes, such as skiers, experience. Many skiers develop cold induced asthma, often called skier's asthma. This occurs due to acute airway obstruction when cold air gets down into the lungs and damages tissues.

Inspired air is conditioned (warmed and humidified) by the upper airways to prevent cooling and desiccation of the lung parenchyma. Although this process is usually successful, under severe conditions such as strenuous exercise in frigid environments unconditioned (cold and dry) air penetrates into the peripheral airways.

In the OSU equine study, horses were exercised on a treadmill while breathing in chilled (4°C) air. After exercising, a bronchoalveolar lavage was performed to test for inflammation, cytokines (chemicals that can damage the lungs) and chemicals that can suppress the immune function in the lungs and lead to infection. Horses that exercise in cold weather experienced peripheral airway mucosal injury due to the penetration of unconditioned air. Furthermore, these results suggest that airway cooling and desiccation may be a factor in airway inflammation commonly found in equine athletes. Results of this study support the hypothesis that exercising while breathing cold dry air alters the airway cytokine profile. The study did not find an increase in inflammatory cells, but as the cellular response takes longer to occur, this study many not have been long enough for it to occur. These results support the contention that exercise while breathing cold air can actually contribute to the development of asthma. The data further raises the possibility of local suppression of cell mediated immunity thought the increased expression of interleukin-10.

Basically, the take-away message from these studies are that horses' lungs can be damaged when strenuously exercised in cold temperatures. If the temperatures get really cold, keep the exercise light to prevent pulmonary problems, especially if your horse has heaves.

Cardiovascular: The cardiovascular system (heart and blood vessels) react to cold by increasing the blood pressure and heart rate. It also reduces the amount of blood that flows closest to the skin in order to preserve core body temperature. The reduces blood flow to the skin can lead to frostbite. Th is lack of blood leads to the eventual freezing and death of skin tissue in the affected areas. Again, it is probably wise to reduce the intensity of your ride so that your horse's heart does not have to work so hard.

Musculature and Joints: Muscles take longer to warm up in the cold weather and arthritic joints may ache and need more time to loosen up. If you are riding, even if you are riding less than you do in the warmer months, don't stop any joint supplements that normally help your horse. He will need them just as much, if not more, in the cold weather. You can also consider a quarter sheet to cover your horse's hind quarters. This will help to keep some heat in, without being restrictive, especially if your horse is body clipped. This brings up the question of whether or not to clip. If your horse gets sweaty when ridden, it is probably a good idea to so some sort of body clip, to help him cool out quicker. A sweaty horse will get very cold in cold weather if not properly cooled out dried off. There are many different types of clips so choose one that is right for your horse and your situation.

Energy and Calories: Exercising in cold weather uses more energy than in warmer weather. Glycogen stores (glucose stored in the liver) is used up five times faster in cold weather. Once this is used up, the body start to convert fat for energy, which is less efficient. Make sure that any horses that will be working hard in cold weather are receiving an adequate number of calories.

Hydration: Water consumption should be carefully monitored in the equine athlete who is working in cold weather. Dehydration occurs in cold weather just as much as it does in warm weather. Flavored electrolytes in feed or water may entice your horse to drink more If your horse is dehydrated, he will have reduced blood volume. that in turn, will make it harder for his already hard working heart to try to work harder to pump less blood. Make sure that your horse has plenty of fresh, liquid water around. A full frozen water trough does no good! Some horse prefer water warmed, so consider using trough and bucket warmers.

Feet: Take care when there is ice and snow on the ground. Slippery conditions can lead to a whole host of musculoskeletal problems. If your horse is shod, consider snow pads to keep snow and ice from balling up on the bottom of his feet. Always pick out any snow or ice to help prevent slipping. Borium on the shoes can add traction, as can caulks if needed.