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

This study  was conducted to evaluate the effects of replacing fish meal with barley protein concentrate (BPC) on digestive enzyme activity and  hepatic enzymes of Caspian salmon (Salmo trutta caspius), with initial weight mean 16.53±1.1g, in a 8 week study in a design completely randomized with 5 treatments, each with 3 replications. 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 were significantly different in different experimental treatments (p<0.05). However, there was no significant difference in LDH between different treatments (p>0.05). There was no significant difference in Pepsin enzyme activity between fish that fed with experimental diets up to 75% replacement and control treatment (p>0.05). The activity of Chymotrypsin and Aminopeptidase in different treatments showed a significant difference compared to control (p<0.05). There was no significant difference in in Trypsin and alkaline phosphatase activity between fish that fed with experimental diets up to 50% replacement and control treatment (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. Therefore it can be concluded that BPC levels up to 50% of the diet are tolerable for the Caspian salmon, but when it goes higher than this level, will probably result in an increase in anti-nutrients,­ a decrease in nutrient uptake, low diet palatability, and  have adverse effects on fish growth.