2.5. Statisticalanalysis
The data of growth performance, tissue weight and lymphocyte proliferation, immunoglobulins, and cytokines were sub- jected to ANOVA using the GLM procedure (SAS Inst. Inc., Cary. NC). The data were analyzed as a 3 × 2 factorial arrangement with the factors in the model being the dietary SIDT level, E. coli challenge and their interaction. For intestinal morphology which was repeatedly measured at different locations, a repeat measure analysis of variance was employed. The levels of SIDT and challenge or non-challenge of E. coli were used as the between subject factors. The individual pig was used as the experimental unit. An alpha level of P