Dietary supplementation of probiotics improves survival and growth of Rohu (Labeo rohita Ham.) hatchlings and fry in outdoor tanks

Low survival (20-30%) and slow growth at early stages of Rohu, Labeo rohita have been major obstacles in meeting the demand of fry in Asia. Three experiments were conducted for 30 days each to evaluate the potential benefits of three multi-strain probiotics in three different stages of juvenile Rohu (hatchling-8 days old, fry-38 days old and advanced fry-68 days old) on the survival and growth. In this study, four different types of treatments were used; namely, T1: Control, i.e. feed without any dietary supplements, T2: feed with Lactobacilli, Bifidobacterium, yeast, Spirulina and phytase, T3: feed with Lactobacillus, yeast, seaweed and amylase, and T4: feed with Lactobacilli, Bacillus and yeast only. Hatchlings fed with T2 feed showed highest survival (74.7%), which is about 25% improvement in comparison to the survival of the Control group (49.9%). Similarly, T3 (60%) and T4 (61.5%) showed at least 10% increment in survival as compared to that of Control (T1). The hatchlings in T2 group had significantly higher (p < 0.05) final weight (0.53 g) compared with T1, T3, and T4 which had final weights of 0.30 g 0.46 g, and 0.39 g respectively. Specific growth rates of T2 and T3 were found significantly higher (p < 0.05) in hatchlings. In fry stage, the feed with all the probiotic mixtures showed significantly higher specific growth than the Control. However, these probiotics had no clear effect on the survival at the fry stage and afterwards. In advanced fry stage, there was no significant difference (p > 0.05) in final weight and specific growth rate among the treatments. Present study indicated that positive effects of multistrain probiotics on the survival and growth can be seen only at hatchling and fry stages, but not later stages.