Evaluation of solid‐state fermented protein concentrates as a fish meal replacer in the diets of juvenile rainbow trout, Oncorhynchus mykiss
2018
Moniruzzaman, M. | Bae, J.H. | Won, S.H. | Cho, S.J. | Chang, K.H. | Bai, S.C.
We evaluated four fermented protein concentrates (FPCs) as a fish meal replacer in juvenile rainbow trout, Oncorhynchus mykiss. Ten diets were formulated to contain low‐temperature fish meal (LT‐FM), Vietnam fish meal (VT‐FM) and four types of FPCs as fish meal replacers (FPC‐A, B, C & D) at 30% and 50% FM replacement levels. FPC‐A was a mixture of solid‐state fermented soybean meal (SBM) and corn gluten meal (CGM) with Bacillus subtilis; FPC‐B was pretreated acid‐hydrolysed FPC‐A; FPC‐C and FPC‐D were FPC‐A + 2% shrimp soluble extract (SSE) and FPC‐B + 2% SSE, respectively. Triplicate groups of fish (average 15.4 g) were fed one of the experimental diets for 8 weeks. At the end of the feeding trial, fish fed the LT‐FM, FPC‐B, FPC‐C and FPC‐D diets showed significantly higher growth performance at 30% FM replacement than those of fish fed the FPC diets at 50% FM replacement. Fish fed 30FPC‐B, 30FPC‐C and 30FPC‐D diets showed higher weight gain (WG) than fish fed 30FPC‐A diet. Haematological parameters showed no clear trends among the experimental groups. Superoxide dismutase, lysozyme and myeloperoxidase activities were found to be higher in fish fed the LT‐FM, FPC‐A, FPC‐B, FPC‐C and FPC‐D diets at 30% FM replacement than in fish fed the FPC diets at 50% FM replacement. Antinutritional factors such as α‐ and β‐conglycinin, glycinin, trypsin inhibitors or zein were absent in FPC compared with SBM and CGM. Intestinal villi length and muscular thickness were significantly reduced in fish fed the VT‐FM and FPC diets at 50% FM replacement compared to fish fed the LT‐FM and FPC diets at 30% FM replacement. The results show that FPC‐B, FPC‐C, FPC‐D could replace up to 30% of LT‐FM in juvenile rainbow trout.
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