Evaluation of the Efficacy of Fermented By-product of Mushroom, Pleurotus ostreatus, as a Fish Meal Replacer in Juvenile Amur Catfish, Silurus asotus: Effects on Growth, Serological Characteristics and Immune Responses

The present experiment was conducted to evaluate the efficacy of dietary fermented by-product of mushroom, Pleurotus ostreatus, (FBPM) as a fish meal (FM) replacer in juvenile Amur catfish, Silurus asotus. A total number of 225 fish averaging 5.7±0.1 g (mean±standard deviation) were fed one of the five experimental diets formulated to replace FM with FBPM at 0%, 5%, 10%, 20%, and 30% (FBPM(0), FBPM(5), FBPM(10), FBPM(20), and FBPM(30), respectively). At the end of eight weeks of the experiment, average weight gain (WG) of fish fed FBPM(0) or FBPM(5) were significantly higher than those of fish fed FBPM(20) or FBPM(30) diets (p<0.05). However, there was no significant differences in WG among the fish fed FBPM(0), FBPM(5) or FBPM(10), and between fish fed FBPM(10) or FBPM(20), and also between those fed FBPM(20) or FBPM(30) diets. Lysozyme activity of fish fed FBPM(0) or FBPM(5) were significantly higher than those of fish fed FBPM(10), FBPM(20) or FBPM(30) diets (p<0.05). The chemiluminescent response of fish fed FBPM(5) was significantly higher than those of fish fed FBPM(0), FBPM(20) or FBPM(30) diets (p<0.05). Broken line regression analysis of WG suggested that the maximal dietary inclusion level for FBPM as a FM replacer could be 6.3% without any adverse effects on whole body composition and on serological characteristics. Therefore, these results may indicate that the maximal dietary inclusion level of FBPM as a FM replacer could be 6.3% in juvenile Amur catfish.