Page 30 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Applied Physiology of Body Fluids in Dogs and Cats 19

TABLE 1-9 Respiratory Water Losses of Panting Mammals*
Respiratory Water Loss Percentage Heat
Species Weight (kg) (g/min) (g/day) Production Lost

Dog 16 0.326 469 57
Cat 3.5 0.029 41.2 9.4

Data from Chew RM. Water metabolism of mammals. In: Mayer WW, Van Gelder RG, editors. Physiologic mammalogy, Vol II: mammalian reaction to
stressful environments. New York: Academic Press, 1965: 43–177.
*Temperature, 41˚ C; relative humidity, 32%.

TABLE 1-10 Effect of Diet on Water Intake in Cats

Ratio of Total
Dry Matter Intake Food Water* Water Drunk{ Total Water Intake Water to Dry
Food (g/day) (g/day) (mL/day) (mL/day) Matter

Dry 76.9 17.4 7.4 1.7 (8.8) 167.2 40.1 (>90) 174.6 41.6 2.3 0.2
Canned 35.2 7.2 116 23.6 (76.8) 22.8 12.8 (14) 139.0 31.4 3.9 0.3

Data from Seefeldt SL, Chapman TE. Body water content and turnover in cats fed dry and canned rations. Am J Vet Res 1979;40:183–185.
*Figures in parentheses represent approximate percentage of diet that was water.
{
Figures in parentheses represent approximate percentage of total water intake that was drunk.

3000
quiet, sick animals, the major obligatory water loss occurs
via urine (assuming no other major contemporary fluid
loss, such as in diarrhea or vomitus). The renal solute load
and obligatory renal water loss decrease because the ani-
mal is not eating. However, animals in a catabolic state
2000
obviously do produce urea and ions for excretion as a
Water intake (ml/day) result of catabolism of lean body mass. Figures for renal
solute loads generated from endogenous sources are
not readily available in the literature. Water requirements
of a sick animal may be increased if the animal is febrile,
1000
having seizures, or experiencing abnormal losses, such
as in vomitus or diarrhea. These contemporary water
needs are in addition to the maintenance water required
to maintain zero balance during inanition and inactivity in
the presence of diminished but still present obligatory
urinary water losses.
CD CBD SMD SDD DD
The volume of water drunk increases as the water in
Food type
Figure 1-9 Effect of food type on water intake in dogs. Each the diet decreases (see Table 1-10). Dogs maintain a
column represents the total daily water intake (mean SD) for four uniform total water intake when food water is decreased
dogs fed different diets. The solid area shows the amount of by commensurately increasing drinking (see Fig. 1-9).
However, cats may not increase drinking enough to
endogenous food water; the clear area shows water drunk. CD,
maintain total water intake when consuming a diet low
canned; CBD, canned meat and biscuit mixture; SMD, SDD,
intermediate moisture foods; DD, dry. (From Burger IH, Anderson in water (see Fig. 1-10). Cats receiving dry food diets
RS, Holme DW. Nutritional factors affecting water balance in the may ingest insufficient water. This issue has been
dog and cat. In: Anderson RS, editor. Nutrition of the dog and cat. investigated extensively as a contributing factor in the
Oxford, UK: Pergamon Press, 1980: 149.)
development of lower urinary tract disease in cats. Some
investigators believe that a low ratio of total water intake
animals do not have access to water from food, total water to dry matter in the diet predisposes a cat to lower urinary
intake may decrease drastically. However, the water tract disease. Diets with a ratio of total water to dry matter
requirement of such animals is probably quite low. In greater than 3 have been suggested as an aid in the