Many horse owners will have noticed their horses or ponies drinking less water in this cold weather, something I mentioned last week in my post about being colic aware. Researchers have found that cold weather can reduce water intake in horses by 6-14%, and free water intake was directly related to ambient temperatures in the range of -20 to 20 degrees centigrade.
Water temperature as well as ambient temperature has an effect on water intake of horses, who will tend to drink less cold water than warm water, in cold weather. Adding a kettle or flask of hot water to your horse’s water bucket or trough can help encourage them to drink more, which is important if they are being fed dry forage such as hay.
You might also have found that your horses and ponies are eating less hay, if they are on free choice forage. A reduced water intake reduces feed intake, which is probably just as well, since a horse drinking very little water but eating a dry diet such as hay, is at an increased risk of gut impaction.
The feed a horse eats affects their water intake because of the variable amount of water different feeds contain. Dry feeds such as hay and compound feed contain about 15% water, yet pasture grass can contain as much as 80% water. A horse may not drink any extra water at all whilst grazing growing grass pasture in spring or summer. Horses on dry diets will drink about 5 litres of water for each 100 kg of bodyweight, which is 25 litres for a 500 kg horse. Individual differences occur, however, and some will drink more than this, and some less. Working horses drink more to compensate for losses in sweat, and total water intake of a 500 kg horse in hard work in a hot, humid environment could be up to 92 litres per day.
The total amount of time a horse spends drinking per day is very small, and some research has shown that it is just 1 to 8 minutes. Taking water to horses in buckets intermittently but in voluntary amounts is enough for their maintenance needs, so leaving non-working horses with access to water at all times is not necessary. Some horses will, however, drink more with free access to water so for working horses it is recommended that they have free access to water.
Water intake can be measured easily with bucket-watered horses, but for those with automatic waterers, meters might be a useful tool to monitor water intake. Horses can tolerate water restriction relatively well, but they will die from a complete lack of water much more quickly than a complete lack of feed.