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

Abstract

The use of Tasco (air-dried Ascophyllum nodosum) as a feed supplement for ruminants has been reported to affect rumen fermentation and reduce Escherichia coli 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 E. coli O serogroups in rams were investigated. Rumen total bacteria and archaea were linearly reduced (P < 0.001) and protozoa were linearly increased (P < 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 E. coli population was linearly reduced (P < 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 E. coli but had only minimal impacts on rumen fermentation in rams. IMPORTANCE 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 Ascophyllum nodosum, 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 Escherichia coli populations and specifically reduced the prevalence of Shiga toxin-producing E. coli 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.

Keywords: Ascophyllum nodosum; Escherichia coli; Tasco; ram; rumen microbiome; seaweed.

FIG 1

Distribution of microbial phylotypes among differed seaweed levels. Venn diagrams were constructed for all of the microbial phylotypes analyzed, including bacterial phylotypes at the phylum, family, genus, and species levels and archaeal phylotypes at the genus and species levels. Among the phylotypes analyzed, those of 12 bacterial phyla, 20 bacterial families, 41 bacterial genera, and 60 bacterial species; 5 archaeal species; and 5 protozoal species were present in all four diets and were considered the “core microbiota.”

FIG 2

PCoA clustering for the bacterial and archaeal profiles at the species level. R1 to R8 are ram identification numbers. Tasco-based clusters were observed in most of the animals.

FIG 3

Tasco-affected microbial species. Mean values for each diet and data collected from individual rams were plotted. Most of the changing trends for these eight species observed in each animal were similar to those found for the mean values. On the y axis is the proportion of the community accounted for by the species.

FIG 4

Relative abundances of the major microbial KEGG metabolic pathways. The values on the x axis indicate the proportions of the functions listed.