부산대학교 도서관

Simple Summary: Creatinine is a marker commonly employed to quantify the amount of urine produced by dairy cattle, when a representative spot urine sample is collected. Combined with urine nitrogen content, the latter allows the measurement of the urinary nitrogen excretion, which is needed to partially assess the environmental impact of dairy farming. However, when urine is sampled, a quota of ammonia nitrogen tends to volatilize, potentially leading to an underestimation of the content of this element. This issue is normally prevented by sample acidification with sulphuric acid which, along with diluting the sample itself, could chemically alter the creatinine content, leading to bias in N excretion quantification. The purpose of our study was to assess whether acidification could affect the creatinine content and detection in urine, and the results demonstrate that acidification can influence its measurement in urine samples from dairy cattle. 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 < 2 (Group 1)); addition of an equal volume of distilled water (1 mL of distilled water in 30 mL of sample) to investigate dilution effects (Group 2); or storage without any acid or water treatment (Group 3). An analysis of creatinine levels was carried out using the Jaffe method. The Friedman test was employed to compare urine groups across treatments, and the Bland–Altman test was used to assess the agreement between measurements in Group 1 and Group 3. Urinary creatinine values were statistically different (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. [ABSTRACT FROM AUTHOR]