The Effects of Replacing Fish Meal with Enzymatic Soybean Meal on the Growth Performance, Whole-Body Composition, and Health of Juvenile Gibel Carp (Carassius auratus gibelio)

Fish meal (FM) constitutes the main, expensive component in aquatic diets. However, the supply of FM is no longer sufficient to sustain global aquaculture production. This study had the primary goal of assessing if the replacement of FM with enzymatic soybean meal (ESBM) can affect the performance of growth and immunological response in juvenile Gibel carp. Juvenile fish with an initial weight of 45.02 & PLUSMN; 0.03 g were arbitrarily assigned to 18 fish cages of 1 m3 each, then fed with diets of different levels of ESBM (0% (control group), 4%, 8%, 12%, 16%, and 20%) for 159 days. These diets corresponded, respectively, to the replacement levels of 0% (control group), 20%, 40%, 60%, 80%, and 100% FM by ESBM. For the parameters of growth and whole-body composition, no obvious differences were found between the control group and other replacement levels (p > 0.05). Similarly, none of the replacement levels showed significant effects for alanine transaminase (ALT), total cholesterol (TC), alkaline phosphatase (ALP), and glucose (GLU) levels (p > 0.05). Malondialdehyde (MDA) levels, as well as the activities of superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in plasma, were not significantly affected at all replacement levels, according to the findings of this study (p > 0.05). The replacement level of 60% significantly increased the activities of catalase (CAT), whereas the replacement levels of 20% and 100% markedly decreased the activities of this enzyme (p < 0.05). Hepatic and intestinal tissues in this study did not show obvious alterations at all levels of replacement.