Does Acidification Affect Urinary Creatinine in Dairy Cattle?

Abstract

Nitrogen content in urine plays a crucial role in assessing the environmental impact of dairy farming. Urine acidifications avoid urine nitrogen volatilization, but potentially lead to a degradation of creatinine, the most dependable marker for quantifying total urine excretion volume, affecting its measurement. This study aimed to assess how acidifying urine samples affects the concentration and detection of creatinine in dairy cattle. In this trial, individual urine samples from 20 Holstein lactating dairy cows were divided into three subsamples, allocated to 1 of 3 groups consisting of 20 samples each. Samples were immediately treated as follows: acidification with H2SO4 (1 mL of acid in 30 mL of sample) to achieve a pH p < 0.001) between Group 1 (median 48.5 mg/dL; range 36.9–83 mg/dL), Group 2 (median 47.5 mg/dL; range 36.5–80.7 mg/dL), and Group 3 (median 48.9 mg/dL, range 37.2–84). Bland–Altman analysis demonstrates agreement between Group 3 and Group 1. The measurement of urinary creatinine using the Jaffe method is affected by sample acidification, but the use of creatinine as a marker for total urine output could remain a viable tool when urine samples are acidified.

Keywords

• urinary nitrogen
• urine acidification
• urine spot sampling
• urinary markers in lactating cows