Water Deficiency
Inadequate water intake is quite detrimental. With the exception of inspired oxygen, a deficiency of water produces death more rapidly than a deficiency of any other substance. The first noticeable effect of inadequate water intake is decreased dry feed intake, followed by decreased physical activity and ability. Inadequate water intake is also believed to increase the risk of intestinal impactions and colic. Water deprivation for 24, 48, and 72 hours decreased the normal resting horse’s body weight 4%, 6.8%, and 9%, respectively, when the ambient temperature was 63–81F (17–27C). At an ambient daytime maximum temperature of 104F (40C), body weight decreased 11 to 13% after 60 hours, and 14 to 16% after 72 hours of water deprivation. Signs of dehydration, such as dry membranes and mouth and sunken eyes, are not evident until at least a 6% loss of body weight has occurred. Less than one-half this amount of dehydration is likely to decrease physical performance. Thus, the horse’s physical performance ability is decreased long before a water deficiency induced dehydration can be detected from the horse’s appearance.
Inadequate water intake occurs when water is poorly palatable or accessible. Palatability is best determined by tasting the water and, if there has been a change in the water or its source, comparing its taste to that to which the horse is accustomed. Poor palatability may be due to poor water quality. Water may be poorly accessible for many reasons, such as if electric heaters with wiring problems cause the animal to be shocked when attempting to drink, or if water is frozen over. Ambient temperature induced variations in water temperature may not alter water intake. Although this situation has not been studied for horses, cattle drink similar amounts of cold or warm water, although individual cattle or horses may have a preference. Cattle, and therefore possibly horses, will consume sufficient snow or crushed ice to meet their water needs if snow or ice is available but water isn’t. However, in doing so, the total amount of water and feed consumed will be reduced.
This article is from Feeding and Care of the Horse, second edition, by Lon D. Lewis, Lippincott Williams & Wilkins, 1995. Reprinted with permission from the publisher.
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