The Effect of Weaning Stress on the Levels of Shiga Toxin-producing Escherichia coli and Fecal Butyrate-producing Bacteria in Young Calves

Introduction: To ensure better beef safety, pre-harvest control strategies targeting Shiga toxin-producing Escherichia coli (STEC) have attracted a lot of attention. Our previous study showed that higher levels of certain butyrate-producing bacteria (BPB) corresponded with lower STEC shedding levels in young un-weaned calves and the amount of BPB changed as the calf age increased.

Purpose: The purpose of this study was to evaluate the effects of weaning stresses on BPB and the STEC shedding levels.

Methods: One hundred and nineteen calves were used in this study. The calf body weight, fecal STEC and O157 were determined 2-days before and 10-days after the weaning time. The gene copy numbers of butyryl CoA:acetate CoA transferase (BCCT) in feces was used to determine the abundance of BPB via a SYBR Green Real-time PCR.

Results: Weaning reduced the calf body weight (ANOVA, P < 0.05), increased the STEC shedding level (from 2.35 ± 1.60 to 3.05 ± 1.04 log CFU/g fecal sample, Wilcoxon signed ranks test, P < 0.05) but had no effects on E. coli O157 levels (P > 0.05). High STEC shedders (calves that shed more than 4 log CFU/g of STEC) had significantly lower BPB than none-STEC calves before and after weaning (Mann-Whitney U test, P < 0.05). Weaning procedure lead to an increase in BPB levels (Wilcoxon signed ranks test, P < 0.05).

Significance: The data confirmed that correlations exist between STEC shedding and BPB levels. Weaning is a step that can change both the BPB and STEC and can serve as an additional potential STEC control opportunity during pre-harvest stages.