Exploratory Study of the Urine Protein-to-Creatinine Ratio in Apparently Healthy Horses

Currently, there is relatively little published information on the urine protein-to-creatinine (UPC) ratio in horses, a parameter commonly used in dogs and cats. The aim of this study was to determine the reference range of UPC in urine samples of apparently healthy horses and to assess the influence of age and sex. Urinalysis and the determination of urinary protein and creatinine concentrations and ratios were performed. A total of 118 urine samples from apparently healthy horses were included in the study: 10 from foals younger than 6 months and 108 from horses older than 1 year. The median UPC for foals younger than 6 months and horses aged 1-4 years, 5-10 years, 11-17 years and older than 18 years were 0.074, 0.073, 0.070, 0.083, and 0.070, respectively. Using the non-parametric Kruskal-Wallis test, statistically significant differences were found between the youngest age group and both groups of adult horses (i.e., 5-10 years and 11-17 years); however, these differences were not confirmed by the General Linear Model, likely due to the small sample sizes in some categories. There was no effect of sex on UPC. The indicative reference range was set for the group of horses aged 5-17 years as 0.02-0.18.