Effects of Replacement of Fish Meal by Soy Protein Isolate on the Growth, Digestive Enzyme Activity and Serum Biochemical Parameters for Juvenile Amur Sturgeon (Acipenser schrenckii)

摘要

Amur sturgeon, Acipenser schrenckii Brant, is a riverine resident sturgeon species in the Amur River, which has become one of the popular sturgeon culture species in China (Zhuang, 2002), however there have been few nutritional studies for evaluations of alternative dietary protein sources. Fish meal (FM), owing to its nutritional quality, is a widely used and expensive protein component of fish diets (Carter and Hauler 2000; Naylor et al., 2000). Partial replacement of fish meal by cheaper ingredients of either animal or vegetable origin in aquatic animal feed is necessary because of the rising cost and uncertain availability of fish meal (Kaushik, 1990; Morales et al., 1994). Plant protein sources, which are more consistently available and cheaper to produce than FM, have been extensively used in combination with FM in practical feed. Among the plant protein sources considered, soybean protein has been preferentially used for replacement of FM due to its high protein content, fairly balanced amino acid profile (Min et al., 2009; Ao et al., 2010) and global presence. Methionine and lysine are the most limiting amino acids in diets containing high levels of soybean meal (SBM). El-Saidy and Gaber (1997, 2002) reported that soybean meal supplemented with 1.00% methionine or 1.00% methionine and 0.50% lysine can totally replace FM in Nile tilapia diets. The substitution of FM with plant protein could have a positive effect on production costs (Hardy, 1996). However, the presence of antinutritional factors like enzyme inhibitors often limit the use of plant ingredients in fish feed as they affect protein digestibility, causing adverse physiological effects and reducing growth (Olli et al., 1994). An enzyme inhibitor is any substance that reduces the measured rate of an enzyme-catalyzed reaction (Whitaker, 1994). Growth is often been reduced in fish fed diets where soybean meal replaces all the FM (Shiau et al., 1987; Reigh and Ellis, 1992; Floreto et al., 2000).