Effect of dietary water intake on urinary output, specific gravity and relative supersaturation for calcium oxalate and struvite in the cat

Abstract

It has been reported that daily fluid intake influences urinary dilution, and consequently the risk of urolithiasis in human subjects and dogs. The aim of the present study was to investigate the role of dietary moisture on urinary parameters in healthy adult cats by comparing nutritionally standardised diets, varying only in moisture content. A total of six cats were fed a complete dry food (6·3 % moisture) hydrated to 25·4, 53·2 and 73·3 % moisture for 3 weeks in a randomised block cross-over design. Urinary specific gravity (SG), urine volume, water drunk and total fluid intake were measured daily; relative supersaturation (RSS) for calcium oxalate (CaOx) and struvite was calculated using the SUPERSAT computer program. Cats fed the 73·3 % moisture diet produced urine with a significantly lower SG (P,0·001) compared with diets containing 53·2 % moisture or lower. Mean RSS for CaOx was approaching the undersaturated zone (1·14 (SEM 0·21); P ¼ 0·001) for cats fed the diet with 73·3 % moisture and significantly lower than the 6·3 % moisture diet (CaOx RSS 2·29 (SEM 0·21)). The effect of diet on struvite RSS was less clear, with no significant difference between treatment groups. Total fluid intake was significantly increased (P , 0·001) in the 73·3 % moisture diet (144·7 (SEM 5·2) ml, or 30 ml/kg body weight per d) compared with the 6·3 % (103·4 (SEM 5·3) ml), 25·4 % (98·6 (SEM 5·3) ml) and 53·3 % (104·7 (SEM 5·3) ml) moisture diets, despite voluntary water intake decreasing as dietary moisture intake increased. Cats fed the 73·3 % moisture diet had a higher total daily fluid intake resulting in a more dilute urine with a lower risk of CaOx when compared with the lower-moisture diets.The extent to which cats are able to adjust the amount of water they drink in relation to the moisture content of their diet has been a source of investigation over the last 30 years. Cats fed an all meat or wet diet, which typically contains in excess of 75 % moisture, will voluntarily drink only small quantities of water (1,2) . Although cats drink more water when offered dry diets, they do not drink amounts that would be expected to compensate for the significant reduction in moisture content of these diets (2) .It is believed that cats adjust their water intake such that they effectively excrete their renal solute load. Since cats fed dry food have a lower total water intake than when fed wet food, it would suggest that the absolute water requirement to dilute the renal solute load is lower than that resulting from a wet-food diet. This means that cats fed wet or natural diets may consume water in excess of any physiological requirement.Dry cat foods have been implicated as a risk factor for cats susceptible to feline lower urinary tract disease (3) , while feeding wet diets has been shown to reduce the recurrence of calculi and signs of idiopathic cystitis compared with dry food (4) .While the benefits of wet food are thought to be attributed to the increased water intake and related increase in urine volume, additional ...

The effect of changing the moisture levels of dry extruded and wet canned diets on physical activity in cats

“…In the study of Buckley et al . ( 16 ) a 73·7 % moisture diet was fed and drinking water intake was 30 ml/kg BW per d; for the present study this was 0·17 ml/kg BW per d when the wet diet was fed and 0·88 ml/kg BW per d when the dry with added water diet was fed. It appears that the higher moisture content of the canned diet in the present study (82 %) provided the great majority of the cats’ requirements.…”

“…In the study of Buckley et al . ( 16 ) a dry diet was hydrated with water to obtain four dietary treatments with moisture levels of 6·3, 25·4, 53·2 and 73·3 %. Water intake increased when dietary moisture level increased.…”

Treatment effect, adherence, and safety of high fluid intake for the prevention of incident and recurrent kidney stones: a systematic review and meta-analysis

“…Importantly, this meta-analysis confirmed the effectiveness of fluid therapy for primary and recurrent stone prevention. Although the type of fluid intake in most studies was not clearly defined [10,11,13–17], both increased water intake [26] and increased general fluid intake [27] resulted in higher urine output. A number of studies [11,12,15] in this meta-analysis demonstrated that high fluid consumption to achieve a minimum urine volume of 2.0–2.5 L/d (as recommended by AUA and ACP guidelines [5,6]) significantly reduced the risk of incident and recurrent kidney stones.…”

Etiopatogenia Da Urolitíase Em Cães

“…Independente de quaisquer outras alterações predisponentes à urolitíase que possam estar presentes, o fator predisponente primordial e necessário para a formação de todos os tipos de cálculos urinários é a supersaturação urinária por substâncias cristalogênicas (OSBORNE et al, 1995;NEUHAUS et al, 2000;KOEHLER et al, 2008;ULRICH et al, 2008;BUCKLEY et al, 2011;OKAFOR et al, 2014). Desse modo, a produção de urina concentrada e com altos níveis de minerais calculogênicos é o fator de risco mais importante para o desenvolvimento dos urólitos (BUCKLEY et al, 2011).…”

“…Desse modo, a produção de urina concentrada e com altos níveis de minerais calculogênicos é o fator de risco mais importante para o desenvolvimento dos urólitos (BUCKLEY et al, 2011).…”