Potential of processed animal protein versus soybean meal to replace fish meal in practical diets for European catfish (Silurus glanis): growth response and liver gene expression

A 9-week study was conducted to evaluate the potential of processed animal protein (PAP) in comparison with soybean meal (SM) to replace fish meal (FM) in practical diets for European catfish, Silurus glanis, on growth performance, liver transaminase activities and expression of growth-related genes. Seven isonitrogenous (440gkg(-1) crude protein) and isoenergetic (16.70MJ/kg) practical diets were formulated by replacing 0 (control), 30%, 60% and 100% FM with either SM or PAP. Each diet was randomly assigned to triplicate groups of 25 fish per cages fixed in the pond. Fish fed the diet substituted 100% FM from SM or PAP had lower (p<.05) growth performance, feed efficiency and protein retention compared to control and other groups. The decreased growth performance occurred concomitant with a decline in the expression level of liver GHR/IGF-I axis genes. The gene expression and activity of liver protein metabolism enzymes also positively correlated with growth performance. Findings of this study indicated that both SM and PAP were equally effective in replacing FM up to 60% in the practical diet of Silurus glanis. Total replacement of FM either with SM or PAP induced negative influences on growth and feed utilization.