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 quality 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 fish were dissected to obtain total contents of intestinal segments, and faeces were stripped from the remainder. The inhibitors decreased protein digestibility from 93 to 70%. Cysteine accumulated increasingly in the small intestine with increasing dietary inhibitor level. A linear relationship between intestinal proteolytic activities and protein digestibility was seen. Lipid digestibility was not significantly affected.