Statistical analyses
Digestibility coefficients and growth performance data were analysed using the MIXED procedure of SAS (version 9.3, SAS Inst. Inc., Cary, NC, USA) with pen as the experimental unit. Overall G:F for each pen was calculated by dividing overall pen weight gain by overall pen feed intake. Normality and homogeneity of variance for each variable were confirmed by UNIVARIATE procedure with ‘Normal’ option and GLM procedure with ‘Hovtest = Levene’ option, respectively. For diet CATTD and energy value and overall G:F data, the model included CPC inclusion level as fixed effect and block was included as random effect. Weekly and overall growth performance data (except overall G:F) were analysed as repeated measures. The model included CPC inclusion level; week and their interactions as fixed effects and block as random effect with week as the repeated term. Pen nested within dietary treatments (CPC inclusion level) was the subject of the repeated measures. The first-order ante-dependence [ANTE(1)] variance-covariance structure was used based on the Bayesian information criterion (BIC) fit statistics. Initial BW was included as a covariate to analyse growth performance data and affected (P < 0.05) ADFI and ADG but not G:F (P > 0.05). Two single-degrees of freedom orthogonal polynomial contrasts were used to test linear and quadratic effects of dietary inclusion of CPC (Littell et al., 2006). To test the hypothesis, P < 0.05 was considered significant.