Studies on supplemental effect of Antarctic krill, Euphausia superba meal in the diets of fish. II. Extraction of growth promoting fractions from non-muscle krill meal of Euphausia superba and its effect on fish growth.

Abstract

Following the previous study on the nutritional quality of the Antarctic krill Euphausia superba meal on the growth of some fishes, this study was conducted mainly to examine the effects of the various soluble fractions (70% MeOH, acetone, ethyl ether and water soluble fractions) separated from the extracts of the non-muscle krill meal which was subjected to two extraction procedures (MeOH: CHCL3 extraction and 70% MeOH extraction). The growth promoting effect of each soluble fraction was tested by supplementing an equivalent amount separately to the test diets and carrying out 45-day feeding experiment on red sea bream Chrysophrys major and black sea bream Mylio macrocephalus. The test diets containing the 70% MeOH soluble fraction of the MeOH: CHCl3 extract showed significantly greater growth than the diets containing other soluble fractions. The diet containing 70% MeOH extract also showed substantial gain in weight. The residue portion from the 70% MeOH extraction showed better growth rate than the control diet, which implied the incomplete extraction by the 70% MeOH extraction procedure and the factor being still remained in the residut portion. Based on this bioassay study, a procedure for isolation of the factor that promotes growth in the fish tested is proposed.