Statistical analyzed

Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC, USA). The individual animal and individual pig were the experimental units for analyzing the data from the digestibility trial. The UNIVARIATE procedure of SAS was used to check normal distribution of model residuals and equal variances. The residual versus the predicted plot procedure was used to identify outliers. The model included the inclusion level of cottonseed oil for all measurements. Orthogonal polynomial contrasts were used to detect linear and quadratic responses to inclusion level of cottonseed oil. The REG procedure of SAS was used to estimate the Y-intercept of the regression line for determining endogenous loss of AEE, and the slope was used to determine the TTTD for AEE for cottonseed oil. The level of significance adopted was 5% (p<0.05) to assess differences among means.