Frequency of diarrhea was calculated by counting pig days with diarrhea score of 3 or greater. Alertness score of each pig was assessed visually each day with a score from 1 to 3 (1 = normal, 2 = slightly depressed or listless, and 3 = severely depressed or recumbent). Every pig was alert throughout the experiment and was given an alertness score of 1 (normal) each day; thus, those data are not reported. Before weaning, fecal samples of sows that produced the piglets destined for these experiments were collected to verify absence of β-hemolytic coliforms by plating on blood and MacConkey agars (more detailed procedures are presented below). No β-hemolytic coliforms were detected in the feces of the sows. Fecal samples were collected from the rectum of each pig on d 0, 3, 6, 9, and 12 and kept on ice during transport to the laboratory. When it was not possible to get a bulk sample because of the absence of feces or watery diarrhea, a cotton swab was used to collect the sample. Samples were processed within 2 h after collection. Each sample was plated on blood agar to differentiate β-hemolytic coliforms (generally gray and shiny colonies; complete
lysis of red blood cells surrounding colonies) from non- β-hemolytic coliforms. Growth on MacConkey agar was compared with blood agar to support that hemolytic
colonies on the blood agar were correctly identified as E. coli (generally flat pink colonies). Plates were incubated at 37°C and were read 24 h after plating.