Air-Dried Brown Seaweed, Ascophyllum nodosum, Alters the Rumen Microbiome in a Manner That Changes Rumen Fermentation Profiles and Lowers the Prevalence of Foodborne Pathogens

This study explores how dietary supplementation with the brown seaweed Ascophyllum nodosum (Tasco) influences rumen microbial populations, fermentation, and pathogen shedding in rams. Across increasing inclusion levels (0–5%), Tasco significantly altered the rumen microbiome, reducing total bacterial and archaeal populations while increasing protozoa. Despite these shifts, overall fermentation output remained stable, although the proportions of key volatile fatty acids changed. Notably, Tasco supplementation led to a marked reduction in total E. coli populations and decreased prevalence of several pathogenic serogroups even when these bacteria were still present in the rumen, suggesting a protective effect that persists through the lower digestive tract, suggesting potential benefits for food safety. Importantly, these microbial and pathogen-related changes occurred without negative impacts on animal growth or overall rumen function. The findings indicate that A. nodosum may serve as a strategic feed additive to modulate the rumen ecosystem and reduce pathogen shedding in livestock production systems.