Extracts of laminarin and laminarin/fucoidan from the marine macroalgal species Laminaria digitata improved growth rate and intestinal structure in young chicks, but does not influence Campylobacter jejuni colonisation

Promoting growth performance, while limiting the proliferation of bacteria such as Campylobacter jejuni, in the post-hatch period is a key goal of the broiler industry. Therefore, the objective of this study was to evaluate the effects of supplementing the diet with Laminarin and Fucoidan extracts on growth performance, small intestinal morphology and function, immune response and Campylobacter jejuni colonisation following an experimental challenge in young chicks following dietary supplementation. The experiment consisted of three diets: 1) basal diet; 2) basal diet + 250 ppm Laminarin (LAM); 3) basal diet + 250 ppm LAM + 80 ppm FUC (LAM/FUC). Day old Ross chicks (n = 135), were housed in groups of three, with 15 replicates per treatment group. On day three, all chicks were orally gavaged with 0.1 ml 106 colony forming units of C. jejuna On day 13, caecal digesta samples were collected for quantification of C. jejuni and Lactobacillus. ileal tissue was also collected post-slaughter in order to examine small intestinal morphology and the gene expression of targets related to gut health. The mean total intake for the chicks fed the LAM, LAM/FUC and basal diets during the experiment (day 0-13) were 411 g, 411 g and 373 g respectively, with chicks fed the LAM and LAM/FUC supplemented diets having increased feed intake compared to the basal diet fed chicks (P < 0.05). Chicks offered diets containing LAM and the LAM/FUC combination had higher (P < 0.05) total weight gain (262 g and 254 g respectively) compared to the basal diet 243 g. Dietary inclusion of LAM/FUC combination increased feed conversion ratio (FCR) (1.68 g/g vs 1.77 g/g) compared to the basal diet (P < 0.05). Chicks offered the LAM and LAM/FUC diet had increased ileal villus width compared to chicks offered the basal diet, while chicks fed the LAM diet had increased villus height compared to chicks fed the basal diet (P < 0.05). Chicks offered the both the LAM and LAM/FUC supplemented diets had increased gene expression of the tight junction protein CLDN1, compared to chicks fed the basal diet (P < 0.05). The gene expression of the measured intestinal nutrient transporters was unaffected by dietary supplementation (P > 0.10). There was no effect of LAM or LAM/FUC extracts on the proliferation of C. jejuni or on Lactobacilli numbers in the caeca. In conclusion, supplementation with LAM or LAM/FUC in the post-hatch period improved growth rate, positively modified small intestinal architecture and impacted the intestinal immune response, but did not impact the extent of C. jejuni proliferation. Supplementation of the diet with LAM provided beneficial effects over supplementation with LAM/FUC in relation to FCR, villus height and aspects of the immune response.