Urine Concentration in Healthy and Diseased Dairy Cows during the First Month after Calving: Comparison of the Refractometry and Reagent Strip Methods.

Gregorio José Alc&aa

Abstract

Osmolality is a standard parameter to measure urine concentration, however clinicians often use refractometry or reagent strip to measure urine specific gravity (SG). Objective To evaluate refractometry and reagent strip for urine SG determination compared with osmolality, and to determine the range of urine concentration in healthy and diseased cows during the first month after calving. Methods Urine samples were obtained from 197 Holstein cows during the first month after calving and analyzed by reagent strip and refractometry immediately, and then frozen until osmolality determination.. The animals were assigned to two groups: healthy and diseased animals. Results Refractometry SG showed a good correlation with osmolality, but there was no correlation between them and SG by reagent strip. The mean urine osmolality was 781 mOsm/kg in healthy and 677 mOsm/kg in diseased cows. Conclusions Refractometry is a sensible device to use at a clinical level in cows to determine urine concentration, but not reagent strip. Urine concentration in dairy cows during the first month after calving was lower than previously reported as reference range in bovines, being even lower in diseased cows.