Page 39

3—
Water

Water is undoubtedly the most important nutrient; it is vital to the functioning of all living cells. The body of the adult dog contains about 60 percent water (Gaebler and Choitz, 1964), and this proportion is even higher in the puppy. The body has a limited capacity to store water, and water deprivation causes death much more quickly than does deprivation of food.

Dogs obtain water in liquid form, from food, and as a consequence of oxidation of hydrogen during metabolism, the latter known as metabolic water. Oxidation of 100 g protein yields about 40 g metabolic water; 100 g carbohydrate, about 55 g metabolic water; and 100 g fat, about 107 g metabolic water. In general, about 10 to 16 g metabolic water are produced for each 100 kcal of energy metabolized. Thus, a dog consuming 2,000 kcal ME per day may derive 200 to 320 g water from body metabolism.

Water gain (whether from liquid water, food, or metabolic water) is balanced by water loss, principally through the urine, lungs, skin, and feces. In the lactating bitch, a considerable amount of water is secreted in the milk.

Under normal conditions, the body water content is remarkably constant. Therefore, water intake plus metabolic water must balance water outgo. The dog can cope with a large fluid intake by virtue of a readily adjustable urine volume, but the unsalvageable water losses of the body dictate the minimum intake. In the growing puppy and the idle adult, voluntary water intake will usually range from 2 to 3 times the dry matter intake. During lactation, hot weather, or severe exertion, water intakes may reach 4 or more times dry matter intake.

The individual dog's requirement for drinking water is self-regulated, depending on factors such as type of food, environmental temperature, amount of exercise, physiological state, and temperament. The need can be met by permitting free access to water at all times or by offering water at least 3 times a day. A dog should not be allowed large amounts of cold water immediately following violent exercise, because of the dangers of water intoxication. When the total ration consists of soft moist foods, which contain an intermediate amount of water, or of dry-type dog foods, water is a necessary adjunct to feeding.



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Page 39 3— Water Water is undoubtedly the most important nutrient; it is vital to the functioning of all living cells. The body of the adult dog contains about 60 percent water (Gaebler and Choitz, 1964), and this proportion is even higher in the puppy. The body has a limited capacity to store water, and water deprivation causes death much more quickly than does deprivation of food. Dogs obtain water in liquid form, from food, and as a consequence of oxidation of hydrogen during metabolism, the latter known as metabolic water. Oxidation of 100 g protein yields about 40 g metabolic water; 100 g carbohydrate, about 55 g metabolic water; and 100 g fat, about 107 g metabolic water. In general, about 10 to 16 g metabolic water are produced for each 100 kcal of energy metabolized. Thus, a dog consuming 2,000 kcal ME per day may derive 200 to 320 g water from body metabolism. Water gain (whether from liquid water, food, or metabolic water) is balanced by water loss, principally through the urine, lungs, skin, and feces. In the lactating bitch, a considerable amount of water is secreted in the milk. Under normal conditions, the body water content is remarkably constant. Therefore, water intake plus metabolic water must balance water outgo. The dog can cope with a large fluid intake by virtue of a readily adjustable urine volume, but the unsalvageable water losses of the body dictate the minimum intake. In the growing puppy and the idle adult, voluntary water intake will usually range from 2 to 3 times the dry matter intake. During lactation, hot weather, or severe exertion, water intakes may reach 4 or more times dry matter intake. The individual dog's requirement for drinking water is self-regulated, depending on factors such as type of food, environmental temperature, amount of exercise, physiological state, and temperament. The need can be met by permitting free access to water at all times or by offering water at least 3 times a day. A dog should not be allowed large amounts of cold water immediately following violent exercise, because of the dangers of water intoxication. When the total ration consists of soft moist foods, which contain an intermediate amount of water, or of dry-type dog foods, water is a necessary adjunct to feeding.