Evaluation of the protective effect of the acid-tolerant engineered bacterial strain M. elsdenii H6F32 as a probiotic fed to sheep duringthe lactic acidosis challenge

This study was conducted to determine if adding the acid-tolerant engineered bacterial strain M. elsdenii H6F32 to the rumen of sheep would reduce the risk of lactic acidosis. Lactic acidosis were induced by feed challenges in three groups of six sheep intraruminally dosed with wheat. In each group, sheep were not supplemented(C) or supplemented with the original bacterial strain M.elsdenii H6(H6) or the acid-tolerant engineered bacterial strain M.elsdenii H6F32(H6F32). Compared with C, the concentrations of ruminal lactic acid were decreased and the pH were increased both in H6 and H6H32(P<0.05). Moreover, the engineered strain H6H32 had the much better ability to decrease lactic acid and increase pH. Meanwhile, a greater concentrations of total VFA were in H6F32. The concentrations of ruminal acetate and butyrate in H6F32 were lower than that in C and H6. However, the propionate was much higher in H6F32. Conclusions about protection against lactic acidosis by the acid-tolerant bacterial strain M. elsdenii H6F32 could be reached. It may be that the engineered strain H6F32 could grow well and increases the microbial fermentative activity and increased VFAs production in the rumen at the expense of lactate during the lactic acidosis challenge.