An experiment was conducted to determine whether the undigested high molecular fraction (HMF) of soybean protein restricts the growth of yellowtail through impairment of lipid digestion and absorption. Soybean meal (SBM), soy protein isolate (SPI), digested SPI (DSPI) and digested and purified SPI (DPSPI) were used as experimental diets. | JOURNAL OF SCIENCE OF HNUE Chemical and Biological Sci. 2013 Vol. 58 No. 9 pp. 112-122 This paper is available online at http EFFECTS OF UNDIGESTED SOYBEAN PROTEIN ON LIPID DIGESTION AND GROWTH OF YELLOWTAIL FISH Seriola quinqueradiata Nguyen Phuc Hung1 and Peerapon Khaoian2 1 Faculty of Biology Hanoi National University of Education 2 Faculty of Agriculture Kochi University Japan Abstract. An experiment was conducted to determine whether the undigested high molecular fraction HMF of soybean protein restricts the growth of yellowtail through impairment of lipid digestion and absorption. Soybean meal SBM soy protein isolate SPI digested SPI DSPI and digested and purified SPI DPSPI were used as experimental diets. Fingerling yellowtail fish were fed either a soybean protein or a fish meal FM diet for 8 weeks. The growth performance of DPSPI-fed fish was significantly better than that of fish fed other soybean proteins and was comparable to that of fish fed an FM diet. Plasma and tissue lipid levels of DPSPI-fed fish tended to be higher than in fish fed other soybean proteins. Significantly lower intestinal lipid levels and higher bile acid levels were found in DPSPI-fed fish when compared to fish fed SBM SPI and DSPI. These findings indicate that growth depression in yellowtail fish fed an SBM-based diet could be due to the negative effect the undigested HMF of soybean protein has on bile acid levels and lipid digestion in the fish. Keywords Soybean protein lipid digestion bile acids yellowtail. 1. Introduction Yellowtail fish Seriola quinqueradiata is one of the most produced and economically important aquaculture fish species in Japan. Much research has been conducted to evaluate the effect of replacing all or a part of the fish meal FM diet of yellowtail fish with defatted soybean meal SBM . It has been found that an excessive amount of SBM in a yellowtail diet resulted in inferior growth performance and physiological abnormalities 11 . Among the
