A metabolism cage for quantitative urine collection and accurate measurement of water balance in adult cats (Felis catus)

The objectives of this study were to validate quantitative urine collection and accuracy of water balance measurements of cats housed in specially designed metabolism cages fitted with a urine/faeces collection system. In Study 1, four adult cars with surgically implanted osmotic mini-pumps releasing an accurate amount of C-14-labelled inulin per unit of time, were housed in the metabolism cages. Daily urine and faeces were collected for 16 days under ad-libitum feeding conditions and a 2-day feed restriction period. Recoveries of C-14-inulin in the urine and faeces, as well as creatinine in the urine, of the cats were determined. In Study 2, four adult cats were fed a nutritionally balanced diet and an 8-day conventional water balance trial was carried out. At the start of Study 2, the cats received an intraperitoneal injection of tritiated water to allow determination of total water turnover by the isotope dilution technique. In Study 1 the recovery of C-14-inulin in the urine of the cats over the 18-day collection period was (mean +/- SEM) 97 +/- 2.9% indicating that urine could be collected quantitatively. A mean (+/- SEM) recovery of C-14-inulin in the faeces of 0.9 +/- 0.31% was found indicating negligible to no cross-contamination of faeces with urine. Daily urinary creatinine excretion Nas found to be highly variable, similar to urine volume, and therefore its estimation is In unsatisfactory index of the completeness of 24-h urine collection in cats. A mean (+/- SEM) agreement of 98 +/- 0.3% was found between the water turnover rate of the cars in Study 2 as measured by the conventional balance technique and the isotope dilution technique. The metabolism cage and urine/faeces collection system described in the present study were found to be highly accurate for the quantitative collection of urine and uncontaminated faeces from adult cars. Furthermore, the technical equipment and the experimental procedures described in this work allow accurate determination of the water balance and water turnover in adult domestic cats.