mortality at 4th week in the control (45.8 ± 15.7%) was significantly higher than that in other treatment groups (P < 0.05) and there was no significant difference in cumulative mortality between all the other treatment groups (P > 0.05). The RPS in the Florfenicol group was significantly higher than that in the probotic treatment groups (P < 0.05). There was no significant difference in RPS between the probiotic groups (P > 0.05). The cumulative mortality at the 8th week in the control (83.3 ± 6.7%) was significantly higher than that in the other treatment groups (P < 0.05). However, there was no significant difference in cumulative mortality between the Florfenicol and the PS groups (P > 0.05). The RPS among Florfenicol and PS
groups was also not significantly different (P > 0.05).