An Evaluation of Replacing Fishmeal with Rapeseed Meal in the Diet of Pseudobagrus ussuriensis: Growth, Feed Utilization, Nonspecific Immunity, and Growth-related Gene Expression

An 8-wk feeding trial was conducted to evaluate the effects of replacing fishmeal with rapeseed meal (RM) on growth, feed utilization, antioxidant capacity, nonspecific immunity, and growth-related gene expression of Pseudobagrus ussuriensis (initial body weight 14.0 g). Six isonitrogenous and isoenergetic diets were formulated to contain RM to replace fishmeal at 0 (R0), 10 (R10), 20 (R20), 30 (R30), 40 (R40), and 50% (R50), respectively. The results showed that final body weight, specific growth rate (SGR), feed intake, feed efficiency, and protein efficiency ratio decreased with increasing dietary RM levels. Fish fed the diets with 30% or more fishmeal replaced by RM had significantly lower SGR (P < 0.05). The apparent digestibility coefficient of dry matter, crude protein, and crude lipid decreased with increasing dietary RM levels. Similar trends were observed in immune parameters and the activities of superoxide dismutase and catalase. However, an increasing trend was observed in malondialdehyde. Fish fed the diets with 30% or more fishmeal replaced by RM had significantly lower hepatic aspartate aminotransferase and alanine aminotransferase activities than the control group R0 (P < 0.05). Hepatic insulin-like growth factor I (IGF-I) gene expression level significantly decreased in fish fed Diet R50 compared with the R10 group (P < 0.05). However, the IGF-I gene expression level in muscles significantly increased in fish fed Diet R50 compared with other groups (P < 0.05). Broken-line model analysis based on SGR against dietary RM substitution level indicated that the appropriate substitution level was 17%.