Hydration For Cats

Every living thing needs water to survive. It is vital for regulating temperature, lubricating joints, healthy digestion, and, arguably most important for the domestic cat, it is needed for urine production.¹ Urinary tract disease (idiopathic, infection, crystals, and stones) is at the top of the list of the most common disease affecting cats, and it is estimated that up to 20% of cats (30% of cats over the age of 10) will suffer from chronic kidney disease.^2,3 Of which dehydration is a significant risk factor in developing these diseases.^4,5

The domestic cat has evolved from populations of the African wildcat, Felis sylcestris lybica, leading to the domestic cat having a low thirst drive.⁶ Their desert-dwelling ancestors, having evolved to live in a desert environment with a lack of readily available water sources, also have low thirst drives and are uniquely adapted to utilizing the moisture in their prey as their sole source of hydration.⁷ In fact, wild prey is about 70% water. Even when domesticated cats are seen frequently drinking from their water bowls, they are, in fact, chronically dehydrated if they are not consuming water in their food source.⁸ A cat’s low thirst drive is so low that it leads to them not consuming water until up to 4% dehydration is already present.¹¹ This low-grade dehydration can result in the production of highly concentrated urine, which may lead to urinary tract and kidney disease.

The regulation of cats’ water intake in relation to the moisture content of their food has been studied extensively over the past 40 years.⁹ Let's look at how much water a cat needs to drink based on the type of diet fed. First, we need to know how much water a cat should consume in a day. A cat requires 44 to 66 ml of water per kilogram of body weight per day, including free sources and what they consume with food. This equates to 0.67-1 oz per pound) each day.¹⁰ The amount of water consumed by food type with vary greatly.

As an example, we will look at a cat that weighs 11 lbs (5kg). Its minimum daily water intake should be approximately 220ml or 7.4oz. A cat eating exclusively kibble with an approximate moisture content of 10% that consumes 80 grams of dry food and will only get 8ml or 0.3oz of its daily needs from the food; they would then need to drink an additional 212ml or 7.2oz of water to have balanced hydration. While cats consuming dry diets voluntarily consume more water, they, unfortunately, may not compensate for the comparable reduction in moisture compared to a high-moisture diet.¹¹In contrast to a cat consuming a high-moisture food that is typically 80% moisture typically found in canned, sous-vide, or raw frozen pet foods but could also be accomplished by rehydrating a freeze-dried, dehydrated, or kibble formula. An 11lbs cat would consume roughly 250 grams of food a day and with this 200mls or 6.7oz of water is needed to only consume another 20ml or 0.7oz of water to stay hydrated.  This significant increase in water intake through food has been shown in several studies to improve hydration and health and reduce disease. ^12,13

Cats are amazing creatures that have evolved unique adaptions to survive in harsh desert environments. While these adaptations were once vital to their survival, they are now a cause for concern in the modern pet environment. Many cats' lack of thirst drive can lead to dehydration in some cats, and feeding a high-moisture diet may aid in preventing this chronic low-grade dehydration for these pets. While this dehydration is not visible early on in life, later on, it can result in painful urinary tract issues and debilitating renal disease. The key to preventing these issues is to keep monitoring water intake as the top priority in a cat's diet.

References

1. Is your cat dehydrated? Retrieved from https://www.royalcanin.com/us/cats/health-and-wellbeing/why-should-your-cat-drink-more-water.
2. Burns, K. Creating brighter futures for cats with chronic kidney disease; JAVMA news. https://www.avma.org/javma-news/2021-02-01/creating-brighter-futures-cats-chronic-kidney-disease.
3. Top 10 Reasons Pets Visit Vets. Retrieved from https://www.petinsurance.com/healthzone/pet-health/health-conditions/top-10-reasons-pets-visit-vets/
4. Greene JP, Lefebvre SL, Wang M, et al. Risk factors associated with the development of chronic kidney disease in cats evaluated at primary care veterinary hospitals. J Am Vet Med Assoc. 2014;244:320–327.
5. Rowe E, Browne W, Casey R, et al. Risk factors identified for owner-reported feline obesity at around one year of age: dry diet and indoor lifestyle. Prev Vet Med. 2015;121:273–281.
6. MacDonald ML, Rogers QR, Morris JG. Nutrition of the domestic cat, a mammalian carnivore. Annual review of nutrition. 1984 Jul;4(1):521-62.
7. Bernard MT. Raising cats naturally: how to care for your cat the way nature intended. Lulu. com; 2004 Feb 1.
8. Pierson LA. Feeding Your Cat: Know the Basics of Feline Nutrition. Retrieved February. 2013;2:2019.
9. Forrester SD, Roudebush P. Evidence-based management of feline lower urinary tract disease. Veterinary Clinics of North America: Small Animal Practice. 2007 May 1;37(3):533-58.
10. Beaver, Bonnie V. Feline Behavior. 2nd ed., Elsevier Health Sciences, 2003.
11. Anderson RS. Water balance in the dog and cat. Journal of Small Animal Practice 1982; 23: 588-598.
12. Grant DC. Effect of water source on intake and urine concentration in healthy cats. Journal of Feline Medicine and Surgery. 2010;12(6):431-434. https://doi.org/10.1016/j.jfms.2009.10.008
13. Buckley CM, Hawthorne A, Colyer A, et al. Effect of dietary water intake on urinary output, specific gravity and relative supersaturation for calcium oxalate and struvite in the cat. Br J Nutr. 2011;106(Suppl 1):S128–130..

 

Follow us on LinkedIn for the latest updates on all things happening here at BSM Partners.

About the Author

Dr. Katy Miller works as the Director of Veterinary Services at BSM Partners. She earned her veterinary degree at Ross University and completed her clinical year at Louisiana State University. She previously served for 11 years as the Director of Dog and Cat Health and Nutrition for Mud Bay where she earned multiple certifications and specialized in pet food nutrition, prior to which she practiced general and emergency medicine for seven years. She is also a competitive three-day eventer, licensed falconer, and claims only two (Golden and Mini Doxie) of their nine dogs.