Effects of dietary supplementation with fermented rapeseed and seaweed on parasite infections and gut microbiota in outdoor pigs

Background: Outdoor pig production systems may lead to higher exposure to infections with helminths such as Ascaris suum. Currently, anthelmintic drug treatments are the main strategy for control of helminth infection, but this is considered unsustainable due to the risk of parasites developing anthelmintic resistance. This study investigated the potential anthelmintic effect of a 2% w/w fermented rapeseed-seaweed (FRS) dietary supplement during 11-12 weeks for growing finishers and its effects on parasitic faecal egg counts (FEC), serology, gut microbiota, and systemic inflammation. The FRS comprised 6% Saccharina lastissima, 6% Ascophyllum nodosum, and 88% rapeseed meal, based on dry matter. Two different batches were used for substudy I and substudies II-IV, respectively.Results: Supplementation of FRS tended to lower FEC and incidence of A. suum infection. However, this effect was variable depending on the batch of FRS. Inclusion of FRS in the feed influenced gut microbiota composition, and feeding with the second batch of FRS led to increased relative abundance of a range of Bacteroidetes members, e.g. Prevotella, while the unsupplemented pigs were enriched in various taxa from the Firmicutes phylum, such as Clostridium spp. Furthermore, pigs fed FRS from the second batch showed reduced daily weight gain compared to control-fed animals.Conclusions: Collectively, our results indicate that FRS modulated the microbiota to a composition putatively associated with improved gut health, and may have some potential as a prebiotic or novel feed additive to help reduce helminth infections.