The samples collected for bacterial population analysis were immediately placed on ice until analyseswere conducted later on the corresponding day. On d 35 of each experiment, a 10.0-mL blood sample was collected byjugular vein puncture from 2 randomly selected pigs in each pen using a disposable vacutainer tube without anticoagulant(Becton Dickinson, Franklin, NJ). After centrifugation (3000×g for 15 min at 4◦C), serum samples were separated and storedat −20◦C and later analyzed for concentrations serum immunoglobulins (IgG, IgA and IgM).