Water balance in the dog and cat

Abstract

In respect of its metabolic control of water balance, the cat probably differs as much from the dog as it does in most other respects. In qualitative terms the routes of gain and loss of water are very much the same: in quantitative terms and in its homeostatic response to different environmental stimuli or insults the cat and the dog are rather different. Dogs and cats are among the commonest species with which veterinarians have to deal. They share much the same environment and are treated in much the same way by their owners. They are almost interchangeable as pets. So far as the veterinary profession is concerned, there are a few outstanding differences such as their response to certain drugs, their reproductive behaviour and their range of aggressive and defensive weapons—but they are in other ways treated in a somewhat similar fashion. It is, however, only within recent years that some other outstanding differences have really become identified between the two species. These differences are in aspects of protein, fat and vitamin metabolism which have direct or indirect relevance to feeding cats and dogs. But they are also manifest in water metabolism, which is the subject of this paper. The first part of this paper will deal with some differences in the water metabolism of dogs and cats which are in the scientific literature but are not widely known outside the research field. The second part will describe some of the work which we have been doing on food/water interrelationships of the dog and cat.

A metabolism cage for quantitative urine collection and accurate measurement of water balance in adult cats (Felis catus)

“…The diet fed to the cats in the present study contained 82% moisture and after 2 days of food restriction, urine volume decreased rapidly to approximately 10 ml/kg body weight. This is in line with other observations showing that cats fed moist cat foods have a higher urinary output compared to cats fed semimoist and dry diets (ANDERSON 1982;GASKELL 1989). WAMBERG et al (1996b) also observed a marked drop in urine output of farmed mink fed a moist diet when food was withheld.…”

“…Accurate measurement of water balance in animals is often difficult as many in-and output values have to be determined (ANDERSON 1982) such as food water intake, drinking water intake, urinary water excretion, faecal water excretion, water lost through expired air, etc. Furthermore, an estimate of metabolic water production is required as well as estimates of evaporative losses of water from urine, food, drinking water, etc.…”

Energy and Water

“…25 In the same study, increasing the salt content of the diet caused an increased drinking response in both dogs and cats. For example, in a study of dogs that were fed a diet containing 73% moisture, they obtained 38% of their daily water needs from drinking water.…”

Nutritional therapies to improve health: lessons from companion animals

“…Obesity is the commonest nutritional disease of companion animals. In various countries the prevalence has been reported as being from 19% to 52% in domestic cats (31)(32)(33)(34) and from 22 % to 44 % in dogs (31,(35)(36)(37) . Orthopedic, endocrine, cardiac, respiratory, neoplastic, urinary, reproductive and dermatological disease and reduced resistance to infection have been associated with obesity in dogs and cats (38) .…”