Effects of dietary galactooligosaccharide enriched commercial prebiotic on growth performance, innate immune response, stress resistance, intestinal microbiota and digestive enzyme activity in Narrow clawed crayfish (Astacus leptodactylus Eschscholtz, 182

The present study was carried out to evaluate dietary effects of galactooligosaccharide (GOS) (0, 1, 2 and 3%) on the innate immune response, stress resistance, intestinal microbiota, digestive enzyme activity as well as growth performance of narrow clawed crayfish (Astacus leptodactylus). At the end of a 97-day feeding trial, crayfish fed 2% GOS supplemented diets had significantly higher total haemocyte count (THC), semi-granular cell (SGC) and hyaline cell (HC) counts compared to the other groups (P < .05). Furthermore, the highest catalase (CAT) was in crayfish fed 3% GOS-enriched diet while the highest lysozyme (LYZ) activity was detected in treatments fed 2 and 3% enriched diets (P < .05). Evaluation of autochthonous intestinal microbiota revealed that the total intestinal heterotrophic bacteria (TIHB) counts increased in all GOS fed treatments as well as lactic acid bacteria (LAB) levels in 2 and 3% GOS supplemented groups (P < .05). However, following the replacement of GOS-supplemented diet with the basal diet for 14 days, LAB counts reduced quickly. The highest amylase and lipase activity observed in the groups fed 2 and 3% GOS (P < .05). Moreover, dietary GOS enhanced the THC, SGC and HC count in crayfish fed 1 and 2% GOS as well as CAT activity in 3% GOS-supplemented group (P < .05). These results confirm the advantageous effects of dietary GOS on innate immunity, stress resistance, intestinal microbiota, and digestive enzyme activity in A. leptodactylus, albeit had no significant improvement on the growth performance and survival (P > .05).