Effect of dietary protein level and source on digestive enzyme proteolytic activity in juvenile Senegalese sole, Solea senegalensis Kaup 1850

Abstract

The effect of dietary protein level and protein source on growth and proteolytic activity of juvenile Solea senegalensis was studied. In Experiment 1 fish were fed on four experimental diets containing increased levels of protein (36, 46, 56 and 67 %). In Experiment 2 Senegalese sole were fed on five diets with partial substitution of fish meal by soybean meal, soybean protein concentrate, soybean protein isolate, wheat gluten meal or pea protein concentrate. Results obtained evidenced that growth and proteolytic activity in distal intestine of fish were affected by the quantitative changes of dietary protein. The type of protein source used in the elaboration of experimental diets affected both the amount and the composition of alkaline proteases secreted into the intestinal lumen but without decreasing growth of animals. Juvenile Senegalese sole showed capability to modulate their digestive protease secretion when the concentration and/or source of dietary protein were modified. Quantity and quality of dietary protein affected intestinal protein hydrolysis in Senegalese sole. This study establishes that 30% fish meal protein can be replaced by soybean derivatives without affect intestinal proteases. The replacement with wheat gluten meal or pea protein concentrate should be taken with caution, but further research is needed to establish if growth performance and digestive enzyme physiology of Senegalese sole could be affected by plant protein-supplemented diets in a long-term trial.