Why Is Hydration So Important for Cats?
Cats' ancestors were desert-dwelling animals (the African wildcat, Felis lybica), which evolved highly efficient kidneys for concentrating urine. However, this also means their thirst drive is relatively low. As a result, cats are unlikely to drink enough water on their own and can easily become chronically mildly dehydrated. According to a study by Zoran (2002) published in the Journal of the American Veterinary Medical Association, long-term insufficient water intake is closely linked to urinary tract diseases and kidney problems in cats.
How Much Water Does a Cat Need Daily?
The NRC (2006) recommends that a cat's daily water requirement is approximately44-66 ml per kilogram of body weight, including water obtained from food. Actual needs vary depending on activity level, ambient temperature, and diet type.
| Body Weight | Total Daily Water Requirement (approx.) | Additional Drinking Water Needed on Dry Food Only | Additional Drinking Water Needed on Wet Food Only |
|---|---|---|---|
| 3 kg | 150-200 ml | approx. 130-180 ml | approx. 0-50 ml |
| 4 kg | 200-260 ml | approx. 170-230 ml | approx. 0-60 ml |
| 5 kg | 250-330 ml | approx. 220-300 ml | approx. 0-80 ml |
As the table above shows, cats fed primarily dry food need to actively drink a large amount of water to meet their requirements, but most cats simply do not do this.
Advantages of Wet Food as a Hydration Source
Wet food (canned food, pouches, etc.) typically has a moisture content of 75-85%, far higher than the 6-10% found in dry food. This means each meal of wet food inherently provides a significant amount of water, more closely matching the moisture content of cats' ancestral prey (small prey animals contain approximately 70% water).
A study by Buckley et al. (2011), published in the British Journal of Nutrition, showed that cats fed wet food had significantly higher overall water intake compared to cats fed dry food, even when the latter had ample access to drinking water. This finding underscores the importance of obtaining water through food.
Dry Food vs. Wet Food: A Major Difference in Hydration
| Comparison | Dry Food | Wet Food |
|---|---|---|
| Moisture content | 6-10% | 75-85% |
| Water obtained from food (based on 200g serving) | approx. 12-20 ml | approx. 150-170 ml |
| Dependence on voluntary drinking | High | Low |
| Effect on urine concentration | More concentrated urine | More dilute urine |
| Storage convenience | Better | Requires refrigeration after opening |
According to research by Markwell et al. (1999), increasing dietary moisture content can effectively lower urine specific gravity and reduce the risk of urinary stone formation. This is especially important for cats with a history of feline lower urinary tract disease (FLUTD).
How to Tell If Your Cat Is Dehydrated
Mild dehydration can be difficult to detect, but the following signs are worth noting:
- Skin elasticity test: Gently pinch the skin at the shoulder blades; it should spring back within 1-2 seconds. Slow return may indicate dehydration
- Dry gums: A healthy cat's gums should be moist and pink
- Sunken eyes: In severe dehydration, the eyes may appear recessed
- Lethargy: A dehydrated cat may become listless with decreased appetite
- Decreased urine output: Smaller or fewer urine clumps in the litter box
If you suspect your cat is dehydrated, seek veterinary attention promptly. Severe dehydration may require intravenous or subcutaneous fluid therapy.
Practical Tips to Increase Your Cat's Water Intake
- Add wet food: Even if you can't switch entirely, mixed feeding can significantly boost water intake
- Use a water fountain: Many cats prefer running water, and a fountain can encourage drinking
- Place water bowls in multiple locations: Set up water bowls in different spots around the home for easy access
- Keep water away from food and litter: Place water bowls away from food dishes and litter boxes
- Try different bowl materials: Some cats prefer stainless steel, ceramic, or glass bowls
- Add water to dry food: Add a small amount of warm water to soften dry food (but avoid leaving it out too long to prevent spoilage)
- Offer broth: Unsalted, unseasoned chicken or fish broth can increase water intake and palatability
References
- National Research Council (NRC). (2006). Nutrient Requirements of Dogs and Cats. The National Academies Press.
- Zoran, D.L. (2002). The carnivore connection to nutrition in cats. Journal of the American Veterinary Medical Association, 221(11), 1559-1567.
- Buckley, C.M., Hawthorne, A., Colyer, A., & Stevenson, A.E. (2011). Effect of dietary water intake on urinary output, specific gravity and relative supersaturation for calcium oxalate and struvite in the cat. British Journal of Nutrition, 106(S1), S128-S130.
- Markwell, P.J., Buffington, C.T., & Smith, B.H. (1999). The effect of diet on lower urinary tract diseases in cats. The Journal of Nutrition, 129(7), 1645S-1650S.
- Westropp, J.L. & Buffington, C.A.T. (2004). Feline idiopathic cystitis: current understanding of pathophysiology and management. Veterinary Clinics of North America: Small Animal Practice, 34(4), 1043-1055.