2.5. Calculations and statistical methods
The effect of diet on daily weight gain, daily feed intake and gain/feed was estimated using the Proc Mixed procedure of SAS with diet and series as fixed effects and litter as random effect. The initial body weight was used as a covariate when analyzing daily weight gain and daily feed intake. Because the interaction between diet and series was not significant, it was taken out of the model. The analyses were performed with SAS for Windows version 8.2 (SAS Institute, Cary, NC). When there was an overall effect of diet, at an alpha of P = 0.05, differences between means were compared pairwise using an F-test.