Urine N-acetyl-beta-D-glucosaminidase activity in healthy cattle

OBJECTIVE: To measure urine N-acetyl-beta-D-glucosaminidase (NAG) activity of healthy cattle, using 3 substrates (4-methylumbelliferyl-N-acetyl-beta-D-glucosaminide, sodio-m-cresolsulfonphthaleinyl-N-acetyl-beta-D-glucosaminid e, and p-nitrophenyl-N-acetyl-beta-D-glucosaminide), and to determine the relations between the obtained values and age and sex of cattle. ANIMALS: 50 healthy lactating Holstein-Friesian cows and 10 healthy Holstein-Friesian steers. PROCEDURE: Untimed urine samples were collected, and urine NAG activity was measured, using the 3 aforementioned methods. Urine creatinine concentration also was measured, and NAG activity was expressed as units per gram of creatinine (NAG index). Correlations between urine NAG activity and age and sex of cattle were investigated. Furthermore, correlations among data obtained by each of the 3 methods were determined. RESULTS: Urine NAG activity in cows measured by each of the 3 methods was < 3.0 U/L. Urine NAG activity in steers was significantly higher than that in cows. However, there was no significant difference between the sexes in NAG index. There were no significant differences in mean values of NAG activity and index among cows of various age groups. Individual values of urine NAG activity determined by each method correlated significantly with each other. CONCLUSIONS AND CLINICAL RELEVANCE: Urine NAG activity and NAG index of healthy cattle will be useful for determining diagnostic criteria of renal disease in cattle.