Effect of feeding sun-dried seaweed (Ascophyllum nodosum) on fecal shedding of Escherichia coli 0157:H7 by feedlot cattle and on growth performance of lambs

This study evaluated whether feeding cattle the brown seaweed Ascophyllum nodosum (Tasco) reduces fecal shedding of E. coli O157:H7. In experimentally infected steers, supplementation at 10 g/kg for 14 days or 20 g/kg for 7 days significantly reduced both the frequency and concentration of E. coli shedding compared to controls. Levels of E. coli declined over time in all groups, but treated cattle had lower final bacterial counts and fewer positive samples, indicating a significant pre-harvest intervention effect. Importantly, reductions were not linked to changes in fecal pH or volatile fatty acids, suggesting the effect is mediated by pathways such as immune modulations or inhibition of bacterial attachment.
In lambs, the same supplement did not affect growth performance, feed intake, or carcass traits, indicating it is unlikely to negatively impact productivity.
Overall, A. nodosum supplementation shows promise for improving food safety by reducing pathogen shedding in cattle without compromising performance, though responses vary with dosing strategy and further work is needed to clarify mechanisms.