Abstract
In the present study, the effects of different probiotics mixtures on growth performance, hematology and antioxidant capacity of Asian seabass (Lates calcarifer) juveniles (30 g). In this study, three bacterial mixtures were used that were isolated from the native aquatic species of Khuzestan and the South of the country, which include: different strains of Lactobacillus plantarum, the second group includes L. plantarum with a mixture of L. bulgaricus, L. acidophilus and L. rahamnosus and the third group including the mixture of bacteria of the first and second groups along with the mixture of Bacillus cereus and B. thuringiensis, which were identified through their quorum quenching feature and isolated from Asian sea bass. Four treatments were designed by spraying various bacterial mixture on a basal diet, which included diet (1) control group, where only sterile physiological serum was sprayed on the food diet, diet (2) on which the mixture of bacteria of the first group was sprayed on the diet, diet (3) on which the mixture of bacteria of the second group was sprayed and diet (4) on which the mixture of bacteria of the third group was sprayed and fed to the fish. The other three treatments were fed to the fish with rations number 2, 3 and 4 in two weeks and formed treatments 5, 6 and 7. Fish fed with the experimental diets four times a day up to satiation at 30.5 °C for 100 days. In this study, the fish that were fed with diets 2, 3 and 4 had higher growth than the control (P < 0.05), which was associated with an improvement in food conversion ratio. The fish that were fed every two weeks with diets containing a mixture of probiotics had intermediate growth, but treatment number 5 showed less growth than other groups. The activity of digestive enzymes in fish fed with probiotics showed a relatively increase compared to the control diet. Blood and antioxidant indices were improved in fish fed with diets containing probiotics mixture. During one week of challenge with Vibrio Harvey bacteria, the fish of treatment 4 that were continuously fed with the mixture of all probiotics had the highest survival rate (50%).The expression of interleukin-10 and granulocyte colony-stimulating factor in treatment 4 was higher than other treatments. Also, the fish that were continuously fed with probiotic mixtures had a higher relative expression in the mentioned genes than the fish that were fed with probiotic mixtures once in two weeks. Treatment 4 had more total plasma protein and albumin than other treatments. In conclusion, the use of a mixture of different probiotics increased growth in Asian seabass that associated with improved health indices in this species.
Keywords: Probiotics, Marine fish, Food conversion factor, Hemoglobin, Superoxide