Antimicrobial peptides (AMPs) are promising drug candidates to treat multi-drug resistant bacteria. Commensal bacteria are considered to be part of the host and are known to produce various AMPs. The cow rumen presents an underexplored resource for the discovery of novel microbial enzymes and metabolites, including AMPs. Using functional screening and computational approaches, we identified novel AMPs from a rumen bacterial metagenome. Here, we show the results obtained with some of these AMPs tested against numerous bacterial pathogens, including resistant strains. Data shown that the ruminal AMPs: i) are active against bacterial pathogens, including resistant ones, ii) have low to no toxicity against human cells, iii) do not cause induction of resistance and iv) work in vivo. Our findings demonstrate that host derived AMPs obtained from the rumen microbiome may provide viable alternative antimicrobials for future therapeutic application.