Microbial analysis
For Escherichia coli and Salmonella enumeration, fecal sample of two pigs from each treatments were collected at the end of the experiment. Fresh fecal samples were collected from the rectum of the pigs in sterile polythelene bags. During fecal collection stimulation of internal and external sphincters were applied to avoid contamination of the samples. In brief, 1 g aliquots of feces from each treatment group were diluted in 10 ml of saline solution, after which 1 ml was serially diluted to make dilutions of 101 to 1011. Microbial plates were then inoculated with three dilutions of each. Samples were plated on MacConkey Sorbitol Agar and Salmonella Shigella Agar for E. coli and Salmonella, respectively. Triplicate agar plates were then incubated at 37°C for 24 h. The total number of colonies for each E. coli and Salmonella were enumerated. Finally, the bacterial counts were expressed as log10 cfu/ml.