Water Drinking in Cats

5. Water Drinking in Cats

Perhaps because of their evolutionary history, cats tend to have a relatively low intake of water. Felis lybica, the European cat ancestor, lived in the desert and was able to concentrate its urine to avoid water losses. Today’s cat has kept this ability, but with the risk of forming bladder calculi. Although a cat can be food deprived for several weeks, a few days of water deprivation are enough to put its life in serious danger. Animals have three sources available to meet their water needs:
- Water offered for drinking
- Water in the food
- Water created by the metabolism of nutrients (Beaver, 2003). Water is produced by substrate oxidation (fat providing the greatest quantity but carbohydrates providing the best output).

In a multiple cat home food and water bowls must be spread through out the environment so that all cats may access them easily without encountering cats that they have a conflict with. In many cases this will resolve the anorexia and the cat will begin to eat normal amounts of food. (© Y. Lanceau/Royal Canin - Maine Coon).

Some Pathophysiological Considerations

Water needs for cats vary from 55 to 70 mL/kg BW/day. The requirement is in fact related to the dry matter intake: 2mL per gram of dry matter eaten.

Intrinsic Regulation of Drinking Behavior

Thirst is the sensation which triggers water intake. The signal comes from the lateral hypothalamus, close to the hunger center. Regulation is complex and closely linked to variation of plasma osmolarity, controlled by vasopressin.

Drinking satiation is first triggered by oral stimulation on a short term basis (one hour). Gastric distension interferes later, acting mainly on the frequency of intake. Finally, cellular hydration controls water satiation through complex interactions.

Cats are not as sensitive to water loss as the dog and may not drink additional water until they have lost as much as 8% of their body water (Case, 2003).

Water intake varies depending upon water losses:
- Physiological losses: urination (40 mL/kg/day), feces and respiration, lactation
- Pathological losses: diarrhea, vomiting, edema, skin injuries, diabetes mellitus, renal failure, etc…

A reduction of blood pressure and blood volume also provoking thirst, through the reninangiotensin- aldosterone system.

External Factors that Influence Drinking Behavior

The Composition of the Food

Water intake is affected by food type and moisture content. Cats fed a canned food drink virtually no water since they meet most of their water requirement with their food intake. It is the same with fish or meat fed animals.

Dry food contains only 7-8% water, requiring the animal to consume more water to meet their daily needs. It has been shown that dry food increases fecal water loss but decreases urinary loss (Jackson & Tovey, 1977). However, it is important to mention that, while intake is strongly modified, the general water balance is not modified by the moisture content of the food. Urinary calculi are more strongly linked to the urinary mineral composition and urinary pH than to the moisture content of the diet. The only risky situation occurs when there is a transition from canned to dry diet.

Caloric density does not affect water intake. Increasing the dietary protein level results in increased water intake (due to the increased diuresis required to eliminate urea). Carbohydrates decrease water intake, due the higher output of metabolic water from carbohydrate metabolism. Sodium chloride increases water intake. Hypernatremia (> 160 mEq/L) triggers thirst and water consumption in cats.

Temperature

The drinking behavior of the cat is much less influenced by temperature and effort compared to the dog. This can be readily explained as salivary and perspiration losses are not significant in the cat. To facilitate water intake the temperature of the water must not be too cold (not less than 10°C).

Food Supply

This factor has been better studied in dogs than in cats. In a restricted regimen, the rate of water intake increases to 2.5 mL per gram of dry matter eaten. A one hour per day feeding pattern leads to a decrease of food and water consumption, compared to the ad libitum situation. In this latter context, water intake is linked to the meals. This is a learned process.

Practical Considerations to Encourage a Cat to Drink

Like food intake, cats drink throughout the entire twenty-four hour period. They drink 12 to 16 times a day but water intake each time is small: 10 to 12 mL. Tremendous variation exists between individuals: this is linked to the sum of physiological effects described above.

To help promote optimal water intake, cats should be provide with fresh, clean water daily from easily accessible water bowls. Owners must pay attention that their cat can have access to water at any time. It is dangerous to provide only one bowl in one room, which could remain closed for a period of time, thus preventing the animal to drink enough. A second bowl elsewhere in the house is recommended, particularly when leaving the cats unsupervised e.g., for a weekend.

Spoiled water is rejected by cats. Glass, metal or porcelain bowls are preferred to plastic ones. The location of the water bowl is important: it has to be put at least 50 cm away from the food bowl and the litter. This distance is sometimes critical when the cat is hospitalized. Water must be palatable: cats are extremely sensitive to odors and some can display preferences for water taken from toilets, sink, etc. Some cats prefer electronic water fountains that aerate the water on a regular basis. One way to increase water palatability is to add meat juice, some milk or some salt. Feeding either a canned food or a liquid food is another alternative.

Drinking Disorders

Adipsia or Hypodipsia

Any cause of hyponatremia (such as severe hepatic disease, congestive heart failure, acute kidney failure, nephrotic syndrome) can stop water intake. These causes of adipsia are in fact compensatory mechanisms.

Conditions of the oral cavity (gingivitis, abscess, tumors, ulcers, fractured jaws, foreign bodies, etc.) may reduce drinking, due to either mechanical or painful reasons.

Adipsia may be simply the result of poor water quality (e.g., water left too long in a dirty bowl). It is nevertheless important to remember that water intake will be still nil as far as all water needed will have been supplied by the food!

Polydipsia

Any change of drinking behavior must be carefully evaluated. Water intake becomes pathologic beyond 100 mL/kg/day. Any cause of polyuria (> 50 mL/kg) will logically lead to polydipsia (Table 8).

Plasma osmolarity facilitates the identification of what is primary polydipsia and what is compensatory (Remy, 1986):
- If plasma osmolarity is greater than 310 mOsm/L, polyuria is primary and urinary loss creates polydipsia
- When plasma osmolarity is below 290 mOsm/L, polydipsia is primary and the low osmotic pressure leads to polyuria.

Intake of salty foods (fish scraps…) leads to polydipsia, and then to polyuria.

The average water consumption of a cat depends on the dry matter ingested: around 2mL of water is required for each gram of dry matter consumed. (© Royal Canin).

Polydipsia may be a reaction to stress or a substitution activity of a permanent anxiety. Hypercortisolemia triggers excessive water intake (Landsberg, 2003). Situations of conflict situations must be identified and corrected.

Hypercalcemia linked to secondary hyperparathyroidism can stimulate thirst.

Hepatic failure can lead to polydipsia through decreased renin degradation and increased angiotensin activity.

Conclusion

The data presented provides an understanding of the normal eating patterns of domestic cats. Some of the information is empirical. Others come from research, in both the natural conditions and in the laboratory. Extrapolation from other species and large felids should be avoided.

The data can help veterinarians and pet owners make relevant choices for feeding routines and food types. The domesticated way of life, with increased social relationships and evolutionary predator behavior must be considered when designing feeding protocols.

Medical problems can often contribute to changes in the selectivity and regulation of food ingestive behavior. Obesity is a major feline health problem. Proper client education and feeding regimes can help prevent and control excessive weight gain. The opposite problem of the fussy or finicky cat is only a problem if the cat is losing weight. The real issue is in the owner’s mind and belief.

Behavioral problems related to feeding and drinking can be due to anxiety, inappropriate provisioning of the cats within the home, learned eating patterns or compulsive disorders. A complete medical and behavioral evaluation should enable the clinician to determine the cause of the problem and therefore prescribe appropriate intervention.

Although the integration of the cat into the family can bring well being and happiness to everyone, the veterinarian will also have to explain to owners to avoid "thinking too human" when taking care of the cat, especially when feeding.