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

Abstract

The use of Tasco (air-dried <i>Ascophyllum nodosum</i>) as a feed supplement for ruminants has been reported to affect rumen fermentation and reduce <i>Escherichia coli</i> O157:H7 shedding in feces, but the mode of action behind this phenomenon is unclear. In this study, the effects of four Tasco levels (0, 1, 3, and 5%) on rumen microbiota and rumen/fecal <i>E. coli</i> O serogroups in rams were investigated. Rumen total bacteria and archaea were linearly reduced (<i>P</i> < 0.001) and protozoa were linearly increased (<i>P</i> < 0.001) by increasing levels of Tasco. The relative abundances of seven bacterial species and one protozoal species differed among Tasco levels. With Tasco, 14 predicted metabolic pathways were enriched while only 3 were suppressed. A lower ruminal butyrate concentration is possibly associated with enrichment of the "butanoate metabolism" pathway in Tasco-fed rams. The ruminal total <i>E. coli</i> population was linearly reduced (<i>P</i> < 0.001) by Tasco. Supplementation with Tasco only completely eliminated O121 in the rumen and feces, and higher levels of Tasco (3 and 5%) reduced fecal shedding of serogroups O45, O103, and O111 even though these serogroups were present in the rumen. Our results suggest that Tasco effectively reduced pathogenic <i>E. coli</i> but had only minimal impacts on rumen fermentation in rams. <b>IMPORTANCE</b> Maintaining product safety and reducing the carbon footprint of production are two sustainability goals of the livestock industry. The objective of this study was to study the impact of Tasco, a product derived from the brown macroalga <i>Ascophyllum nodosum</i>, on the rumen microbiome and its function. The inclusion of Tasco altered both rumen and fecal microbiota levels without affecting rumen fermentation. Tasco reduced fecal <i>Escherichia coli</i> populations and specifically reduced the prevalence of Shiga toxin-producing <i>E. coli</i> O45, O103, O111, and O121 in feces. The findings of this study highlight the application of Tasco as a potential feed additive to reduce pathogen shedding in rams without interfering with ruminal metabolism.