Novel Direct Fed Microbials to Control Acidosis and Liver Abscesses in Cattle.

Novel direct fed microbials to control acidosis and liver abscesses in cattle.

Siera K. Rohde¹, Christopher L. Anderson¹, Samodha C. Fernando¹

¹Department of Animal Science, University of Nebraska–Lincoln, United States.

In recent years, the use of antibiotics in food animals has come under great scrutiny. Studies have demonstrated continuous use of antibiotics can result in collections of antibiotic resistance genes within bacteria. Such resistant microbes present in cattle and other livestock species can pose a threat to humans by contamination of food or during handling of animals. As such, developing novel strategies to reduce antimicrobial use while improving animal health and efficiency is critical. One such alternative strategy is the use of direct fed microbials to replace antibiotics. In the current study, we isolated two species of bacteria from the rumen of animals fed a distillers grain plus solubles diet where each could be used to control Streptococcus bovis and Fusobacterium necrophorum populations in cattle. The isolates were tested for their ability to inhibit Streptococcus bovis and Fusobacterium necrophorum using the Kirby-Bauer Disk Diffusion Susceptibility test using Mueller Hinton agar plates with 5% sheep blood. The resulting positive isolates were characterized by 16S rRNA sequencing. The sequence analysis revealed that the isolates belong to the genus Aneurinibacillus (A. migulanus and A. anerinilyticus). The cell extracts of the isolates were used for disk diffusion assays and for growth curve experiments that revealed inhibition of both Streptococcus bovis and Fusobacterium necrophorum by each isolate. Finally, invitro acidosis induction experiments were performed using live cells and cell extracts of A. anerinilyticus to evaluate the control of ruminal pH during acidosis induction. The invitro induction experiments reveled A. anerinilyticus cell extract and live cells can protect ruminal pH (higher pH) better than the induced control. Currently the genome sequencing of the two strains is underway to identify the mode of inhibition. This study demonstrates the potential of direct fed microbials as a viable strategy to control pathogenic and other inhibitory microbial populations in the rumen, decreasing the use of antibiotics.