Late-cutting lipid-soluble alfalfa extract beneficially modulates the colon microbiota to protect mouse body weight during Citrobacter rodentium challenge

Mouse models allow for detailed preliminary research into the health-promoting effects of novel feed additives to identify candidates for livestock application. Alfalfa is a potential source of health-promoting feed additives, but detailed findings on factors that maximize its benefits are lacking. The study objective was to evaluate the effects of feeding late and early alfalfa as hay, aqueous, and lipid-soluble extracts on the body weight (BW) and colon microbiota of mice before and after pathogen challenge. A total of 98 female 6-week-old C57BL/6J mice were weighed and assigned to 1 of 7 diets consisting of basal diet ± hay (9%), aqueous extract (0.25%), and chloroform extract (0.25%) of late and early cutting alfalfa. After 14d, 6 mice/treatment were euthanized for baseline colon digesta sampling. The remaining animals were orally inoculated with Citrobacter rodentium and 4 mice/ treatment were euthanized for colon digesta collection at 4 and 21d post-inoculation (pi). While observed patterns in BW were not statistically significant, numerical improvements in early and late days post-inoculation (pi) indicated a protective effect of lipid-soluble extracts on BW during bacterial challenge. Corresponding to these observations, late cutting chloroform extracts significantly reduced pathogen abundance in the colon at 4dpi while increasing the abundance of beneficial community members at 21dpi (P = 0.02). These findings in mice support future research into the effects of late-cutting chloroform alfalfa extracts in livestock diets.