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Comparative study of digestive enzymes in rainbow and brown trout

The aim of this study was to build up informations and compare activities of digestive enzymes of rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta morpha fario). From the digestive enzyme profile it is possible to predict the ability of a species to use different nutrients. The ability to transform and use the dietary nutrients depends on the enzyme distribution over the digestive tract. Specific activities of alkaline phosphatase (AP), amylase (AMY), lipase (LIP), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamine aminotransferase (GGT) in the tissue samples (liver ; anterior, middle and posterior intestine) were determinated using a automatized biochemical analyser Olympus (AU 6000). Overall, the enzymatic activity in the digestive tract of brown trout was greater than in rainbow trout. Brown trout showed significantly higher values of lipase, ALT and AST activity, while amylase activity and amylase/lipase ratio were significantly lower. These findigs suggests greater and better fat digestibility in brown trout than in rainbow trout. Because of higher amylase activity rainbow trout can better use carbohydrates than brown. Enzymes activities was the highest in the anterior and middle intestine, where the most digestion and absorption processes in fish occured. The study of the digestive biochemistry is a very important in respect of the diversification of the fish species cultivated. Enzyme contents and distibution over the digestive tract is crucial for fish farming and determinating fish nutritrion.

rainbow trout; brown trout; digestive enzymes; amylase/lipase ratio

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