Dose effect of Lactobacillus plantarum on the body weight of mice during pre- and post-challenge periods (n = 6). CONT, control group, treatment with PBS at all period; ETEC, negative group, oral challenge with ETEC on day 15; LDLP, low dose (5.0 × 108 cfu mL−1) group; MDLP, intermediate dose (5.0 × 109 cfu mL−1) group; HDLP, high dose (5.0 × 1010 cfu mL−1) group; LDLP, MDLP, and HDLP groups were infected with ETEC at day 15. There was no significant (P > 0.05) in all groups.