Estimates of daily water requirements have been reported for cats.1 However, no consensus exists for how to define optimal hydration, optimal water intake volume in cats, or the overall impact of adequate hydration on health.2 A basic and limited framework of published research exists on water intake, water balance, and urine variables in cats, with data primarily collected for kennel-housed animals that necessitate citation to work conducted as long ago as the 1970s.1 Daily water intake volume has been reported as milliliters per kilogram of body weight, milliliters per kilogram of dry matter ingested, and milliliters per kilocalorie of ME ingested (water-to-calorie intake ratio).1 All these methods account for the intake of water from a combination of sources including food moisture, FW consumption (drinking), and MW. In general, the daily water-to-calorie intake ratio for water need has been estimated to be 0.6 to 0.73,4 and 0.95 for healthy cats consuming dry and wet food, respectively. Although cats can consume sufficient calories to meet their daily needs regardless of whether dry or wet food is given, this difference in the daily water-to-calorie intake ratio is observed in healthy cats because they drink less water when fed dry food and thus do not consume as much water as they ingest through dietary moisture when eating wet food.1,3,6,a
The currently accepted understanding in regard to these differences in water intake in healthy cats is that the higher total water intake and higher water-to-calorie intake ratio result in greater diuresis in cats that eat wet food. In comparison, although cats that eat dry food have a lower daily water-to-calorie intake ratio, the total water intake is equally sufficient to meet their daily water requirements.1 However, cats with various types of LUTDs appear to benefit from increased total water intake and urine output. Nutritional studies6–9,a,b to investigate health concerns related to LUTDs in cats have provided some evidence that increased water intake can be achieved through modification of dietary moisture content to increase water intake through food6,7,a or of dietary sodium content to stimulate drinking.8,9,b
Research with human patients has revealed that increased water intake leads to increased urine volume and dilution, thus supporting increased water intake as one of the typically recommended methods to help prevent urolith recurrence.10,11 Voluntarily drinking more water is the most common means of increasing fluid intake in people, but this also includes greater consumption of other common beverages.10,12 Although increased total water intake for cats has been achieved through dietary modification or stimulation of thirst mechanisms, to the authors' knowledge, there are no published reports of studies examining the effects of a water supplement on daily water intake, urine dilution, or hydration in this species. Results of 1 study13 indicate increased palatability of water for cats (determined by preference testing) when a liquid nutritional supplement is added, compared with water alone.
A greater understanding of feline water intake patterns, water balance, and urine indices of hydration status is needed. The objective of the study reported here was to evaluate the effects of NW consumption on water intake and indices of hydration in healthy cats fed dry food (kibble). Goals included examination of voluntary TW consumption and characterization of multiple physiologic measures of hydration status prior to treatment, followed by testing for changes in liquid consumption, total water intake, and hydration variables after providing an NW (alone and as a supplement to TW provided separately) for 56 days. The nutrients in the prototype NW primarily included organic osmolytes, glycerol, and amino acids from whey protein and animal digest.
All authors are employed within the R&D department of Nestlé Purina PetCare and conduct nutrition research for the potential use in future commercial applications and products. None of the authors have any conflict of interest or affiliation to disclose related to the equipment used during the study.
Presented as an abstract at the American College of Veterinary Internal Medicine Forum, National Harbor, Md, June 2017.
The authors thank Mark Miller and Sarah Dionne for management and care of cats and coordinating sample collections, Jim Ambrose for operating the QMR unit and generating data for body composition measurements, and Patricia Turpin and Dakota Marti for performing assays of urine and serum samples.
Glomerular filtration rate
Lower urinary tract disease
Quantitative magnetic resonance
Total body water
Urine specific gravity
Xu H, Greco DS, Zanghi B, et al. The effect of feeding inversely proportional amounts of dry versus canned food on water consumption, hydration, body composition, and urinary parameters in cats (abstr), in Proceedings. 39th World Small Anim Vet Assoc Cong 2014;852.
Xu H, Laflamme D, Bartges J, et al. Effect of dietary sodium on urine characteristics in healthy adult cats (abstr). J Vet Intern Med 2006;20:738.
Nestlé Purina PetCare, St Louis, Mo.
Performed by NP Analytical Laboratories, St Louis, Mo.
BD Vacutainer SST tubes, Becton, Dickinson and Co, Franklin Lakes, NJ.
Vapro 5520 vapor pressure osmometer, Wescor Inc, Logan, Utah.
Cobas c 311, Roche Diagnostics, Indianapolis, Ind.
Creatinine Jaffé Gen.2, Roche Diagnostics, Indianapolis, Ind.
HSK-VET veterinary refractometer, Heska, Loveland, Colo.
Human Hydration LLC, Hampton, Va.
pH 11 meter, Oakton Instruments, Vernon Hills, Ill.
Perkin-Elmer Optima 2000 DV, Perkin-Elmer Inc, Shelton, Conn.
ICS-5000, Dionex Inc, Sunnyvale, Calif.
EchoMRI-Infants QMR analyzer, Echo Medical Systems, Houston, Tex.
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Ingredient composition and proximate analysis of an NW used in a study to evaluate the effects of the product on water intake and indices of hydration in healthy domestic cats fed a dry kibble diet ad libitum.
|Whey protein (%)||1.2|
|Potassium chloride (%)||0.100|
|Poultry digest (%)||1.0|
|Crude protein (% as fed)||1.7|
|Crude fat (% as fed)||0.35|
|Crude fiber (% as fed)||< 0.2|
|Phosphorus (% as fed)||0.016|
|Sodium (% as fed)||0.0283|
Mix of guar gum and xanthan gum.