Assessment of Brix values for estimating nitrogen and gross energy concentrations of pig urine: a technical note

The present study aimed to develop equations for estimating the dry matter (DM), nitrogen (N), and gross energy (GE) concentrations in pig urine using Brix values. A total of 96 urine samples were obtained from pigs of 6.0 to 62.2 kg initial body weight fed 12 diets in three experiments. The animals were fed a corn-soybean meal-based diet or a corn diet. The N concentrations in the urine samples ranged from 0.12% to 2.06% and the GE concentrations ranged from 2 to 187 kcal/kg. The urine Brix values were positively correlated with urinary DM, N, and GE concentrations (r = 0.94, 0.87, and 0.93, respectively; p<0.001). The models for estimating urinary DM, N, and GE concentrations were: urinary DM (%) = 0.590×Brix+0.315 (r2 = 0.91; p<0.001); urinary N (%) = 0.0798×Brix+0.148 (r2 = 0.84; p<0.001); urinary GE (kcal/kg) = 11.96×Brix+2.33 (r2 = 0.87; p<0.001), where the Brix value of urine is expressed as %. Overall, the Brix values correlated positively with the DM, N, and GE concentrations in pig urine and can thus be used for estimating the concentrations of these urinary components.