In Consultation With Dr Brian Zanghi: discussing nutrition, the role of a researcher, and the importance of feline hydration

Dr Brian Zanghi is a senior research nutritionist at the Purina Institute, where he has worked for 15 years. His work primarily focuses on canine and feline nutrition, aiming to better understand how nutrition can help maintain overall health in pets. I was able to sit down with Dr Zanghi to discuss nutrition, the role of a researcher, and the importance of feline hydration.

Background into Dr Zanghi’s research: feline hydration studies


The main aim of Dr Zanghi’s research was to evaluate the effects of drinking nutrient-enriched water on the water intake of healthy cats, with the research focusing primarily around two studies. The first study split 18 cats into a test group and a control group. The test group was offered the nutrient-enriched water supplement ad libitum, whereas the control group only received tap water alongside the standardised dry food diet fed to all of the cats.


From days 0 to 10, the test group received only the nutrient-enriched water instead of tap water, and then from days 11 through to 56 they were offered both tap water and the nutrient-enriched water in separate bowls.

Blood and urine samples were collected at predetermined intervals for analysis, with urine collected every 48 hours to assess volume output in the cats.


The cats in the test group that were given the nutrient-enriched water had an increased liquid consumption during the treatment phase, with a higher mean urine output compared to the control group, which was given only tap water. The clinical significance of the study was that offering nutrient-enriched water can increase liquid intake and improve measures of hydration in healthy cats, providing health benefits. The study also emphasised that cats fed a dry food diet may benefit from a greater daily water intake.

The ad libitum study ran for two months, and was a follow up to some preliminary assessments researching the benefits of nutrient-enriched water. The early studies revealed that the liquid was highly acceptable, so researchers were confident in the uptake of the nutrient-enriched water; the cats’ liquid intake was carefully monitored throughout the study.

The second study conducted by Dr Zanghi and his team offered the cats in the test group the water supplement on an incremental dose basis. This study was designed to explore if the cats would drink more if they were offered more, and to determine how incrementally increasing liquid intake influenced urine volume output in healthy cats fed a dry food diet.

The studies, published in 2018 and 2019 respectively, both identified that the nutrient-enriched water increased total water intake and increased total urine output.

Were there any surprising results?

Cats have been found not to have a high degree of thirst sensitivity. In dogs, an incremental increase in serum osmolarity results in an increased desire to drink. In cats there is much less data available to examine, with the relationship between ADH and serum osmolarity currently not well characterised. When serum osmolarity has been measured in cats, high values haven’t been associated with any difference in water intake. This suggests distinct differences in thirst sensitivity compared to dogs – potentially this is an area with scope for further research.

Science behind the scenes: what was the research process like?

“Once the research idea was created, we collected background literature to understand the scope of the research being conducted. We then used this information to develop the experimental design and work out how the study might run,” says Dr Zanghi. “Generating a research proposal which outlines the plans of the research is done much like it is in university facilities. After approval, finalising the protocols and going through the ethical welfare reviews were the next steps to ensure that all aspects of the studies were approved and safe. Once the study was complete, all samples were sent to the lab, and the data was interpreted and statistically analysed. The next part of that process was publishing, and we planned our strategy ahead of time to determine which conferences we would be attending and presenting at.”

Science behind the product: PRO PLAN® HC Hydra Care™

PRO PLAN® HC Hydra Care™ is a new product launched by Purina based on the research conducted by Dr Zanghi and his team. The product contains all of the active ingredients that were evaluated in the research studies, with glycerol – which is recognised as an organic osmolyte – as a key nutritional element. “There were a lot of things to take into consideration when designing the biological composition of the product. The flavour component was important, involving hydrolysed protein sources and amino acids, alongside the composition of mineral levels in the product. The formula of the product is slightly different to what was used in the original research. Hydra Care™ has a slightly thicker viscosity, providing additional texture for the cats and better adherence to the tongue for lapping purposes,” explains Dr Zanghi.

purina hydracare brian zanghi feline hydration and nutrition

How can we better define healthy hydration?

How to better define healthy hydration, especially in cats, is a question that still needs to be more accurately characterised. Dehydrated cats are often seen in practice, presenting with conditions that need to be managed and stabilised. There are different ways of addressing and quantifying hydration in animals, but being able to quantify healthy hydration is a concept that is less well defined.

“This is still something that needs to be established,” Dr Zanghi explains. “It was one of the fundamental objectives of the early work we carried out, and it also underlines the value of the dose titration study we did. Through looking at the incremental increases in water intake, we can then begin to evaluate if there are also any incremental changes in urine output parameters. By assessing those parameters we can detect slight variations and start to ask how we can define healthy hydration better. There are still a lot of basic characteristics that need to be established to better define this area of research further.”

Why is feline hydration important to vets?

It is well recognised that increasing water intake is one way to help support cats with recurrent uroliths, those with FIC, and older cats. Increasing voluntary drinking, as well as providing a higher sodium diet to drive water intake, helps to increase urine flow and output. Through routine clinical assessments looking at parameters such as urine specific gravity, vets can gain better insight into hydration levels, which is something that is well highlighted in the second study by Dr Zanghi that investigates dose titration of the nutrient-enriched water. These measurements can then show vets if a cat’s daily water intake needs to be increased, and can help characterise urinary disease states better.

The future of feline hydration

“There has been lots of research into healthy cats, but there’s an increasing need for clinicians to have more of an understanding of where hydration plays a role for cats that have certain conditions and need extra support,” Dr Zanghi explains. “It’s not a far stretch to say that we’re just starting on this journey, and it’s really significant for cats with upper and lower urinary tract disease. This points us in the direction of having another tool that can be used to examine the water needs of cats, and to generate a better understanding of the water intake requirements of cats with certain diseases.”

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