Nitrogen retention in pigs given diets containing cottonseed meal or soybean meal

Nitrogen (N) retention was determined in female growing pigs fed sucrose-based diets formulated to contain similar ileal digestible nitrogen (IDN) (22.5 g kg−1) and lysine (5.1 g kg−1) with either cottonseed meal (CSM) or predominantly soybean meal (SBM) and synthetic amino acids. The diets were offered frequently (200 g per 3 h) via an automatic feeder. The pigs consuming the CSM diet excreted more (19.6 vs 16.5 g day−1, P = 0.001) urinary N than those given the SBM diet. A greater proportion (56 vs 44%, P = 0.01) of IDN intake was found in the urine of pigs fed the CSM diet than the SBM diet. Thus the N retention of the CSM diet was significantly (17.3 vs 23.3 g day−1, P = 0.007) lower than that of the SBM diet. Overall, these data suggest that the availability of IDN from CSM was inferior compared with SBM, and the N balance assay may be more reliable for predicting N utilization of CSM than the ileal digestibility measurement.