This study was carried out to evaluate the use of creatinine as an indicator of urinary production in sheep. Total creatinine urinary excretion was determined based on data and samples collected from four digestibility experiments previously conducted with lambs maintained in metabolic cages. In all experiments total urinary production was collected during five days in each animal and experimental period. Additionally, in one experiment, urine samples were taken at intervals of two hours during a 24 hours period. Total excretion of creatinine (mean of 660mg day-1) was different among experiments (P<0.01) and animals (P<0.01). The daily excretion as proportion of body weight (mean of 23,2mg kg-1 live weight) was different only among experiments (P<0.01), but was similar among the animals and periods and treatments (P>0.05). In the other hand, the urinary concentration of creatinine was different among experiments (P<0.01), animals (P<0.01) and periods (P<0.05). There were also differences among sampling times through a 24 hours period (P<0.01). The estimate of urinary production based on urinary concentrations of creatinine in spot samples, may be reliable only if, at least in one animal, representative of experimental group, total urine collection be carried out to measure the mean daily excretion of creatinine relative to body weigh. Moreover, spot samples should be collected in different times to constitute a composite sample representative of a 24 hours period.
creatinine; urinary excretion; indicator; ruminants
