EVALUATION OF PROTEIN DIGESTIBILITY IN AQUAFEED USING IN VITRO ENZYMATIC HYDROLYSIS ASSAYS: A PRACTICAL APPROACH

摘要

In vitro digestion is a useful method of predicting the digestibility of experimental feeds. Determining the digestibility of the major nutrient (protein) is one of the main steps in the evaluation of its bioavailability for a given species. Several in vitro methods using digestive enzymes from different sources have been developed and tested. Proteolytic enzymes are supplied either as a combination of individual proteolytic enzymes from commercial companies or as digestive enzyme extracts obtained from the animals under study. Nevertheless, these methods have not been fully validated for industrial use, as the enzymes used were not suitable. In order to determine in vitro protein digestibility, several parameters have been developed, based on the chemical and physiological characteristics of protein digestion. The pH-stat procedure is a kinetic method that directly measures the percentage of peptide bonds hydrolysed in the protein (Dimes and Haard, 1994). The aim of this study is to summarize thedifferent technical protocols that use the pH-stat system for in vitro determination of protein digestibility with digestive enzymes. Species-specific modifications and indications as to appropriate parameters are also described.