Changes in final weight, survival and fatty acids composition of Caspian brown trout (Salmo trutta caspius) fed gamma-irradiated and fermented soybean meal

This study aimed to evaluate the effects of replacing fish meal with gamma-irradiated and fermented, or a combination of irradiation and fermentation soybean meal on average final weight, survival and fatty acid composition of Caspian brown trout (Salmo trutta caspius). For this purpose, soybean meal was treated using the above methods, and then the quality of protein (SDS-PAGE electrophoresis) and total phenolic compounds was evaluated. Fish meal was replaced by soybean meal in 5 diets, including untreated (control), treated with doses of 15 (15ISB) and 30 kGy (30ISB) gamma rays, fermented (with Saccharomyces cerevisiae) (FSB) and irradiated (at a dose of 15 kGy) and fermented (IFSB) soybean meal. Caspian brown trout with average weight of 2.1 ± 0.3 g were fed 5 dietary treatments (3 replicates) using a completely randomized design for 10 weeks. Comparison of proteins in different treatments showed that acidic subunit of the glycinin and β-conglycinin reduced in FISB (irradiated at a dose of 15 kGy and fermented soybean meal). At the end of the experiment, survival rate was 100% in all treatments. The average final weight of fish fed FSB and IFSB diets were significantly higher than the other groups (P<0.05). The present study reveals that Caspian brown trout fed with soybean meal processed with a combination of gamma irradiation and fermentation have better growth performance and gamma rays can be used as a new approach to reducing soybean meal antinutritious.