Abstract

The snakehead Channa striatus is widely preferred by consumers and is often affected by the dreadful disease Epizootic Ulcerative Syndrome (EUS) and encounters losses in capture as well as culture fisheries. Antibiotics, chemotherapeutants and vaccines are now commonly used in aquaculture to prevent/treat fish diseases. Meanwhile an alternative safer way to tackle the disease problem eco-friendly is to improve the resistance of target species by application of probiotics as growth promoters and immunomodulators. The present investigation was attempted to find out the effects of common probiotic strains Bacillus subtilis, Bacillus coagulans and Saccharomyces cerevisiae and commercial probiotic Efinol^®FG on growth performance  and microbiological changes in normal striped murrel C. striatus and also those challenged byAeromonas hydrophila. Probiotics were added to the autoclaved semi moist feed and fed to the fingerlings. Feeding experiment was conducted for 45 days. Growth measurements and total microbial count (TMC) were made once in 15 days for a total period of 45 days. Best SGR and FCR were estimated as a function of Efinol^® FG diet and the difference in weight gain (16.37 g), SGR (4.22) and FCR (2.28) was found to be significantly different (P<0.05) between Efinol^® FG diet and other probiotic diets. TMC is higher in Efinol^® FG fed diet (7.7 × 10⁸ CFU g^-1) than other fed diets. After that the fingerlings from each group were divided into non-challenged (NC) and challenged by A. hydrophila by oral injection (OI) and intramuscular injection (IM). Growth measurements and TMC were made again once in 7 days for a total period of 21 days. The challenged group of control diet (OI and IM) showed a drastic increase from day 1 (3.5 × 10⁸ CFU g^-1) to day 21 (7.1 × 10⁹ - 8.8 × 10⁹ CFU g^-1) whereas the OI and IM groups of all probiotic diets showed a drastic decrease. In the case of OI group Efinol^® FG diet, the decrease was from 7.7 ×10⁸ CFU g^-1 on day 1  to 2.0 × 10⁸ CFU g^-1on day 21. The corresponding decrease in IM group was from 7.7 × 10⁸ CFU g^-1 to 4.5 × 10⁸ CFU g^-1. Regarding the equilibrium between competing beneficial Efinol^® FG and pathogenic A. hydrophila, extension of experimental duration / increase in Efinol^® FG concentration may help to arrive at a conclusion.

Key words: Channa striatus, probiotics, Efinol^®FG, growth parameters, total microbial count.