Dietary Lactobacillus plantarum affected on some immune parameters, air-exposure stress response, intestinal microbiota, digestive enzyme activity and performance of narrow clawed crayfish (Astacus leptodactylus, Eschscholtz)

The present study evaluates the effects of different levels of dietary Lactobacillus plantarum including 10(7) (LB7), 10(8) (LB8) and 10(9) (LB9) CFU g(-1) diet on some immune parameters, stress response, intestinal microbiota, digestive enzyme activity as well as growth performance of narrow clawed crayfish (Astacus leptodactylus). At the end of the feeding trial, LB7 and LB8 treatments had significantly the highest total haemocyte count (THC), semi granular cells (SGC) and hyaline cells (HC) count, total plasma protein (TPP) and phenoloxidase (PO) activity compared to the other groups. Additionally, increased large granular cells (LGC) count and lysozyme (LYZ) activity noticed in crayfish in LB8. Additionally, the highest superoxide dismutase (SOD) and catalase (CAT) activity observed in LB7 compared to the other groups. Microbiological assessments revealed that total autochthonous intestinal heterotrophic bacteria counts (TVC) remained unaffected in different treatments. Nevertheless, autochthonous lactic acid bacteria (LAB) levels were significantly elevated in all L. plantarum supplemented groups and the highest levels observed in LB8 and LB9 treatments. However following the replacement of L. plantarum supplemented diet with the basal diets, no autochthonous LAB detected in LB7 and LAB count reduced in LB8 and LB9 groups. Higher digestive enzyme activity (protease, amylase and alkaline phosphatase (ALP)) observed in the LB8 and LB9 treatments compared to the other groups. Regardless of the inclusion levels, lipase activity increased significantly in all the probiotic supplemented diets. In the present study, improvement of the growth parameters were not found to be significant in all the probiotic supplemented groups. 24 h post air-exposure, no mortality was detected in all the groups. However, dietary administration of L. plantarum elevated the mean THC, SGC and HC numbers and the highest value was observed in crayfish at LB7 treatment compared to the other groups. In addition, crayfishes at LB7 and LB9 demonstrated higher CAT activity among the other groups. These results confirm the beneficial effects of dietary L. plantarum on immune parameters, stress response, intestinal microbiota and digestive enzyme activity of A. leptodactylus.