Water Needs and Hydration for Cats and Dogs

Brian M. Zanghi, PhD
Nestlé Research Centre St. Louis



  • A pet’s hydration status does not remain constant throughout the day, but instead fluctuates between hypo-hydration (dehydration) and hyper-hydration (over-hydration).
  • In cats, the total water intake is higher when ingesting wet foods versus dry due to the moisture in the wet food. Cats drink more water when fed dry food because they self-regulate their water intake to meet their needs, but there is ongoing discussion around their optimal water intake and how we may influence it to improve health.
  • There is no difference in total water intake associated with food type in dogs.
  • In humans, as little as 2% dehydration can cause cognitive deficits. Therefore, our future research in our pets should consider how optimal hydration and daily water intake influences not only metabolic and urological health, but also obesity, brain health, and cognition.



Brian M. Zanghi, PhD- Nestlé Research Center – St. Louis

Dr. Brian Zanghi joined Purina in 2005, where he currently serves as a senior research nutritionist in the Molecular Nutrition Group at the Nestlé Research Center in St. Louis, Missouri. He earned a doctorate degree in canine nutritional physiology from the University of Kentucky in Lexington in 2004. He continued his training at the University of Kentucky as a postdoctoral research scientist working on nutrient metabolism in aging animals. Dr. Zanghi has been studying canine and feline nutrition in the areas of body composition, sleep, cognition, behavior, and hydration to better understand how nutrition can help maintain overall health in adult and older pets, as well as the role nutrition plays in optimizing performance of active dogs. Dr. Zanghi has written several peer reviewed publications in the areas of adult and senior dogs’ locomotor activity patterns, sleep rhythms, body composition, exercise, and cognition.

“How the varying amounts of daily water intake relate to a low, moderate, or high hydration process, along with the prospect of how this impacts long-term health, not only remains to be determined, but could be interesting and possibly very important to consider to improve dietary water recommendations for healthy pets. For pets with some type of urinary tract condition, obesity, and/or geriatric life stage, the need is likely even greater.”