Dietary inclusion of a fermented rapeseed–seaweed blend alters immunity and intestinal microbial activity but not Ascaridia galli burden in laying hens

1. Dietary components that are pre-fermented with lactic acid bacteria have recently attracted attention and may positively affect performance and gut health in poultry. This study investigated whether a commercial feed ingredient (EP199), containing fermented rapeseed meal, wheat bran and seaweed, could control worm burden, intestinal microbiota profiles and intestinal fermentation patterns, as well as immune profiles of layers infected with Ascaridia galli.2. A total of 192, 20 week old Bovans Brown laying hens were randomly allocated into four treatment groups; control diet vs. EP199 diet and experimentally infected (EXP) vs. naturally infected (NAT). The EP199 diet partly replaced rapeseed cake at 6%. The infected hens were either naturally exposed to A. galli contaminated litter or received oral administration of 764 embryonated A. galli eggs per hen at 20 weeks of age for 12 weeks.3. Performance was unaffected by EP199 or infection. However, hens fed the EP199 diet had a significantly lower egg production 3-12 weeks post-infection (pi) compared to the control group (86.1% vs. 90.1%, P=0.044). There was no effect on intestinal worm burden (x=7.98 worms per hen) or immune competence, as assessed by mitogen activation of peripheral blood mononuclear cells (PBMC). Despite similar nutrient profiles of the two diets, the hens fed the EP199 diet had significantly higher caecal levels of specific short chain fatty acids: acetic acid (79.8 vs. 71.0 mmol/kg digesta; P=0.020), propionic acid (35.0 vs. 30.1 mmol/kg digesta; P=0.005) and n-butyric acid (17.3 vs. 14.7 mmol/kg digesta; P=0.015).4. Compared to the control group, hens fed EP199 had a lower humoral A. galli-specific immune response, in terms of IgY serum titres at 10 weeks (2812 vs. 5291; P=0.002) and 12 weeks (10546 vs. 17668; P=0.025) pi. Hens fed the EP199 diet showed a significantly higher frequency of activated CD4+CD8+ T cells (28.7% vs. 21.9%; P=0.045).5. Feeding EP199 at 6% did not have an effect on severity of A. galli infection. However, EP199 showed an immunomodulatory effect and altered caecal microbial activity. Infection method (experimental vs. natural) influenced both the worm burden and immune parameters.