Utilization of Soy Flour by Fingerling Rainbow Trout Having Different Body Size

Abstract

A 6-week feeding trial was conducted 3 times using fingerling rainbow trout Salmo gairdneri with three different body weights (0.7, 5.1 and 8.9 g) to study if there are any differences in utilization of a soy flour with supplemental amino acids. Treatment of soy flour with methanol improved its utilization in all size groups and the efficiency of utilization became better as fish grew. The largest fish showed up to 83-87% of the value performed by the control group fed the yeast diet even though 77 % of the fishmeal was isonitrogenously replaced by methanol treated soy flour with supplemental amino acids. The fish up to 5.1 g did not show any response to multiple supplementation of amino acids simulating the composition of the control diet. Whereas the same treatment showed a tendency to improve the growth and feed efficiency of the largest fish. Activity of trypsin like enzyme in the gastrointestinal tracts of the smallest fish was significantly suppresed when soy flour either treated or untreated with methanol was used as the substrate instead of the fishmeal but the almost identical activity was detected in the largest fish no matter which substrates were used. These results indicate that apparent differences exist in utilization of soy flour and response to supplemental amino acids in fingerling rainbow trout having different body size. © 1989, The Japanese Society of Fisheries Science. All rights reserved.