DIGESTIBILITY DETERMINATION IN FISH USING CHROMIC OXIDE MARKING AND ANALYSIS OF CONTENTS FROM DIFFERENT SEGMENTS OF GASTROINTESTINAL-TRACT

Methods of feed digestibility determination in fish were reviewed. The indicator method, using chromic oxide, was judged most suitable, but the best method of sampling faeces was uncertain. Rainbow trout (Salmo gairdneri, Richardson) were fed an experimental diet containing 1% chromic oxide. Faeces were collected by two stripping methods, and gut contents were obtained by dissection from five zones of the alimentary canal. Analyses of feed, faeces, and gut contents were made, and digestibility of protein, fat, carbohydrate, ash and gross energy calculated. It was concluded that absorption occurs in all parts of the alimentary tract, and that it is important to limit the stripping of faeces for analysis in digestibility studies to the hindmost part of rectum, i.e. from the ventral fin to anus. © 1978.