Is water the most essential nutrient for dogs?

(Too long, won’t read? WATCH Dr. Roberts explain how to keep your dog hydrated!)

Contributor: Dr. Mark Roberts, Ph.D.

When we think about how to keep your dog hydrated, the answer lies in their diet as much as their water bowl. Leading canine nutrition expert, Dr. Mark Roberts, Ph.D., explains why water should be viewed as an essential nutrient for dogs.

Why is water important for dogs?

Water is often regarded as the forgotten nutrient; however, it should undoubtedly be viewed as the most essential (1). It supports numerous physiological functions including regulating temperature, reducing the burden on kidneys, and carrying nutrients and oxygen to cells. Water is also vital for the removal of metabolic waste products, acting as a medium for the process to occur. It is important to understand that the water content of a dog’s body is in constant flux (2), replenishing loss from respiration, urine, saliva, etc. This involves the hormone vasopressin, which is secreted in response to an increase in urine concentration and decrease in blood volume (3).

how does diet affect hydration?

The water content of a dog’s diet raises several questions:

  • If dogs who eat a dry diet, with access to water, can maintain optimal hydration, then would eating a high-moisture diet result in hyperhydration, increased body water turnover and higher hydration status? 

  • Alternatively, if a wet diet is the basis of maintaining optimal hydration, then by default, consuming a dry diet would indicate dogs who might be slightly dehydrated (2).

  • Or, do dogs with access to water maintain an optimal hydration status, whether they are fed a dry diet or a high-moisture diet?

At present, no published data supports hyper-hydration from a high-moisture diet or, by default, dehydration from a dry diet. However, dietary moisture significantly influences total daily water intake and directly impacts the proportion of water intake through drinking.

factors that influence hydration in dogs

There are several factors that can have a role in a dog’s hydration level:

  • Environment: Hot conditions often mean dogs evidently require greater water intake. However, very cold weather can also be challenging for hydration, with drinking water potentially freezing very quickly for dogs that live outside. In these cases, a high moisture diet is vital, ensuring adequate water intake is achieved.

  • Physical activity

  • Age of the animal (4)

  • Body composition

  • Breed

  • Underlying health conditions

Ultimately, diet is recognized as having a crucial role on the hydration status of dogs — both due to moisture intake and macronutrient impact.

The role macronutrients play in hydration

What does this mean? Let’s look at carbohydrates.

Dogs that consume a high-carbohydrate diet produce more carbon dioxide (CO2) than oxygen consumed, compared to dogs fed a low-carb, high-fat diet. This is referred to as the respiratory quotient, or RQ), with a ratio of 1 determined from a carbohydrate dominated diet, in contrast to 0.7 for fat (6). In essence, CO2 is a byproduct of respiration, and must be removed. Dogs achieve this via their breath, therefore higher levels of CO2, (from a high carbohydrate diet) require greater rates of breathing, than that of a high fat diet. As moisture is a component of breathing, dogs on a high-carbohydrate diet expel a greater amount of water than dogs which consume a high-fat diet simply through breathing (7). This can have consequences on heat production, and the ability to breathe through the nose without panting, in turn having a profound impact on hydration status.

Hydration Strategies

So what can we do to help our dogs stay hydrated?

To maximize the hydration status of a dog, a high-fat, low-carbohydrate diet has the biggest influence. Other strategies to try:

  • Adding water to a diet

  • Feeding a diet with an inherent moisture content (such as raw). This is more pertinent in the colder, winter months whereby dogs are less driven to drink water.

  • Another approach to help dogs’ water intake is to add meaty, umami flavors to their drinking water, in the form of bone broths, chunks of thawed meat or by adding crumbs or nuggets of low-carb, freeze-dried meat-based diets.

  • Using warm water in addition to these meat-based components will further help drive dogs to consume fluid.

Applying these strategies will help ensure your dog is both happy and hydrated!

References

1.      Jéquier, E., & Constant, F. (2010). Water as an essential nutrient: the physiological basis of hydration. European journal of clinical nutrition, 64(2), 115-123.

2.      Zanghi, B. (2017). Water needs and hydration for cats and dogs. Proceedings, Nestlé Purina Companion Animal Nutrition Summit. Vancouver, BC, 15-23.

3.      Ramsay, D. J., & Thrasher, T. N. (1991). Regulation of fluid intake in dogs following water deprivation. Brain research bulletin, 27(3-4), 495-499.

4.      Taylor, E. J., Adams, C., & Neville, R. (1995). Some nutritional aspects of ageing in dogs and cats. Proceedings of the Nutrition Society, 54(3), 645-656.

5.      McGrotty, Y. (2008). Diagnosis and management of chronic kidney disease in dogs and cats. In practice, 30(9), 502-507.

6.      Reynolds, A. J., Taylor, C. R., Hoppeler, H., Wiebel, E., Weyand, P., Roberts, T., & Reinhart, G. (1996). The effect of diet on sled dog performance, oxidative capacity, skeletal muscle microstructure, and muscle glycogen metabolism. In DP Carey, SA Norton and SM Bolser (Eds) Recent Advances in Canine and Feline Nutritional Research: Proceedings of the Iams International Nutritional Symposium. Orange Frazer Press, Wilmington, Ohio, USA, 1996.

7.      Hill, S. R., Rutherfurd-Markwick, K. J., Ravindran, G., Ugarte, C. E., & Thomas, D. G. (2009). The effects of the proportions of dietary macronutrients on the digestibility, post-prandial endocrine responses, and large intestinal fermentation of carbohydrate in working dogs. New Zealand Veterinary Journal, 57(6), 313-318.

Katie Shatzer