SOYBEAN PROTEINASE-INHIBITORS AFFECT INTESTINAL TRYPSIN ACTIVITIES AND AMINO-ACID DIGESTIBILITIES IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Rainbow trout (Oncorhynchus mykiss), 265 g kept in fresh water, 1 m(2) surface area tanks, 10 kg per tank were fed diets based on high quali ty fish meal added 0.00, 0.37, 0.74, 1.11 and 1.48% soybean proteinase inhibitors, and chromic oxide as internal marker. After TO days, 10 f ish were dissected to obtain total contents of intestinal segments, an d faeces were stripped from the remainder. The inhibitors decreased pr otein digestibility from 93 to 70%. Cysteine accumulated increasingly in the small intestine with increasing dietary inhibitor level. A line ar relationship between intestinal proteolytic activities and protein digestibility was seen. Lipid digestibility was not significantly affe cted.