Animal by‐products with or without enzymatic hydrolysis completely replacement of fish meal in genetically improved farmed tilapia diets ( Oreochromis niloticus )

Abstract

An 8-week feeding trial was performed to examine the potential of total replacement of fish meal with animal by-products with or without enzymatic components in juvenile genetically improved farmed tilapia (GIFT) diets, Oreochromis niloticus, (mean initial weight, 19.71 ± 0.28 g), reared in RAS system. Five isonitrogenous and isoenergetic diets were formulated with fish meal for the diets with total replacement of the isonitrogenous amounts of enzymatic fish meal (E-FM), chicken liver meal (CLM), enzymatic chicken liver meal (E-CLM), dried porcine solubles (DPS) and enzymatic dried porcine solubles (E-DPS) respectively. The results indicated that the weight gain rate (WGR) and specific growth rate (SGR) in the FM group were significantly higher than the E-FM and E-CLM groups (p < .05), but the specific growth rate (SGR) in the E-CLM group lower than the E-FM group. The feed conversion ratio (FCR) in FM and CLM was significantly lower than the E-FM, E-CLM and E-DPS groups (p < .05), and no significant difference was observed among the FM, CLM and DPS groups (p > .05). The values of the protein retention efficiency (PRE) and protein efficiency ratio (PER) in FM, CLM and DPS groups were significantly higher than the E-CLM group (p < .05). The values of feed intake ratio (FIR) in FM and CLM groups were significantly lower than the E-FM, E-CLM and E-DPS groups (p < .05). There was no significant difference in the whole body contents of moisture, crude lipid and crude ash among the FM and E-CLM groups (p > .05). The whole body contents of crude protein in the FM group were significantly higher than the E-FM, CLM, E-CLM DPS and E-DPS groups (p < .05). The apparent digestibility coefficients (ADC) of dry matter, crude protein and crude lipid in the FM, E-FM, E-CLM and E-DPS groups were not significantly different (p > .05). The serum glucose(GLU), total cholesterol (TCHO) and triglycerides (TG), or the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were not affected by the different treatments (p > .05). There was no significant difference in serum total protein (TP) or albumin (ALB) and between the FM group and other groups (p > .05). There was no significant difference in the serum urea nitrogen (BUN) content in the FM, CLM, E-CLM and DPS groups (p > .05). Fish fed with the CLM and DPS diets had significantly lower hepatic GHR1, IGF1 and IGF2 gene mRNA expression levels than in fish fed the FM diet (p < .05). The present data showed that 6% of dietary fish meal can be totally replaced by the chicken liver meal and dried porcine solubles with no effect on the growth performance of GIFT strain tilapia.