The effects of replacing fish meal with barley protein concentrate on digestive enzyme activity and hepatic enzymes of Caspian salmon (Salmo trutta caspius)

The effects of replacing fish meal with barley protein concentrate (BPC) on digestive enzyme activity and  hepatic enzymes of Caspian salmon (Salmo trutta caspius) in a 8 week study with a weight mean 16.53±1.1g with completely a randomized design with 5 treatments and 3 replications was used. Experimental diets consisted of control diet (without barley protein concentrate) and four diets containing levels of 25, 50, 75, 100% barley protein concentrate. At the end of the experiment, ALP, AST and ALT levels was significantly different in different experimental treatments (p <0.05). However, there was no significant difference in LDH between different treatments (p >0.05).In fish fed with experimental diets pepsin enzyme activity in experimental diets up to 75% replacement with control treatment there was no significant difference (p <0.05). The activity of Chymotrypsin and Aminopeptidase in different treatments showed a significant difference compared to control (p >0.05). In fish fed with experimental diets up to 50% replacement in trypsin and alkaline phosphatase activity compared to control treatment was no significant difference (p <0.05). The activity of amylase and lipase enzymes showed a significant difference between treatments with different levels of barley concentrate (p <0.05). digestive enzymes decreased at higher replacement levels, but in the middle levels of replacement, there was less effectsin pancreatic enzymes. It can, therefore, be concluded that BPC levels up to 50% of the diet are tolerable for the Caspian salmon, but levels exceeding this limit will probably result in an increase in anti-nutrients, a decrease in nutrient uptake, low diet palatability, and adverse effects on fish growth.