The acute effects of a protein‐rich meal on the urinary corticoid:creatinine ratio in healthy dogs

The objective of this prospective crossover study was to investigate the effects of a high‐protein diet on canine urinary corticoid‐to‐creatinine ratio (UCCR). The hypothesis was that meal‐induced hypercortisolism is, as has been shown in humans, a predictable and consistent finding in healthy dogs. Eight clinic‐owned beagles were randomly assigned to one of two groups. The allocation to the groups defined the sequence of a protein‐enriched meal (meal A) or no meal on the first and second days, whereas on the third day all dogs again received an identical meal (meal B) to test reproducibility. Urinary corticoids were measured using a solid‐phase, competitive CLIA on unextracted urine. Contrary to our expectations, consistent incremental responses of the UCCR were not observed (meal A vs. no meal [anova ]: absolute increase, F = 2.546, p = 0.162; relative increase, F = 4.084, p = 0.09; AUC_(UCCR), F = 0.279, p = 0.616). Nevertheless, the robust increases in two dogs above 60% of baseline suggest that the collection of urine prior to feeding likely increases the specificity of the UCCR to discriminate between dogs with and without hypercortisolism.