Abstract
Background:
Microbial and toxin-related challenges are well-documented causes of impaired animal performance. The gastro-intestinal tract is the single largest organ that interfaces with numerous challenges including pathogenic organisms, toxins and other immune activating stimuli. The integrity of the intestinal mucosal barrier is the first and most critical line of defence. There are a number of reports demonstrating the potential of naturally derived feed additives to mitigate the damage derived from toxin or infectious agents on cell culture barrier integrity models but little information on target species tissue. Natural ingredients based on Lithothamnion glaciale (LG) and an extract of Ascophyllum nodosum (ANE) were tested in an ex vivo model using porcine ileal tissue, in the absence and presence of an infectious challenge derived from Salmonella enterica enteriditis (SEE). Read-outs included various parameters on the barrier integrity, tissue histology as well as the immune status of the tissue.
Results:
The SEE challenge significantly impaired barrier integrity (P<0.05), as demonstrated by increased paracellular ([3H]-mannitol) relative to transcellular ([14C]-caffeine) transport. LG and ANE were tested individually at multiple doses and in combination to explore potential synergistic effects. The barrier integrity was positively impacted from the combination of LG and ANE at the low ANE dose, especially following the SEE challenge (P<0.001). The SEE challenge reduced TNF-α expression in the control treatment, which is caused by the downregulation of the inflammatory response immediately after a challenge (P>0.01). The relative expression of the gut barrier protein Cadherin-17 was increased when LG and/or ANE was included (P<0.001), both with and without the SEE challenge. The inflammatory markers tumour necrosis factor-α, Caspase-1, Interleukin-22 and regenerating islet-derived protein-3 γ were affected by the inclusion of LG and/or ANE (P<0.05). A synergistic effect between the two marine bioactives was evident and appears to be dose dependent, with the low dose rate of ANE and the low and medium LG rate being most optimal.
Conclusions:
These results suggest that an optimal combination of marine bioactives can have a significant effect in enhancing gut barrier integrity and immune reactivity when challenged with an intestinal pathogenic bacteria in porcine ileal tissue.
Keywords:
Ascophyllum nodosum; Lithothamnion sp.; Gut barrier; Gut integrity; Marine bioactives; Piglet health; Salmonella infection.