Inclusion effects of jack mackerel meal in diets containing different protein sources for olive flounder (Paralichthys olivaceus)

Abstract

1. Dietary optimum inclusion level of jack mackerel meal for olive flounder (Paralichthys olivaceus, Temminck & Schlegel, 1846)

Feed stimulants are used to incite feeding behavior in fish to improve feed consumption and growth. This study investigated the effect of jack mackerel meal (JM) as dietary attractant and/or stimulants on olive flounder on growth, feed utilization, chemical composition, plasma chemistry, and non-specific immune responses. In addition, the attractiveness of the experimental diets containing various levels of JM to olive flounder was determined. A total of 675 juveniles was randomly distributed to 27 tanks each containing 25 fish (initial weight of 5.3 g) for the 8-week feeding trial. The control diet (JM0) contains sixty percent fish meal (FM). The graded levels (1, 3, 5, 20, 20, 40, 60, and 100%) of JM were included at the expenses of FM, referred to as the JM1, JM3, JM5, JM10, JM20, JM40, JM60, and JM100 diets, respectively. Fish were fed ad libitum in triplicate groups of each diet twice a day for 8 weeks. To determine the attractiveness of the experimental diets, thirty fish were held in the acclimatization chamber at a time and a knockout comparison of the experimental diets was applied. The strongest feeding attractant response of olive flounder was observed in the JM60 diet, followed by the JM40 and JM20 diets, in that order. The greatest weight gain and specific growth rate (SGR) were recorded in fish fed the JM20 diet, followed by the JM40, JM60, JM100, JM10, JM5, JM3, JM1, and JM0 diets, in that order in the 8-week feeding trial. The highest feed consumption was obtained in fish fed the JM20 diet. None of the organosomatic indices (condition factor, and viscerosomatic and hepatosomatic indices), biochemical parameters, non-specific immune activities (superoxide dismutase and lysozyme activities), chemical composition and amino acid and fatty acid profiles of the whole body fish were affected by the experimental diets. The findings of this study demonstrated that the olfactory system incited attractiveness, while the gustatory system regulated the feeding, hence dietary optimal inclusion level of JM seemed to be 20%.

2. Inclusion effect of jack mackerel meal as feed stimulants in diets replacing different levels of fish meal with various animal protein sources on growth performance of olive flounder (Paralichthys olivaceus)

Fish meal (FM) is one of the costliest components in formulating fish feeds, so there is a high need to look for a replacer for FM. Incorporated feed stimulants into fish feeds is a very sustainable aquaculture technique, especially in developing low FM diet to improve feed consumption and growth performance. This study aims to evaluate substitution effect of different levels of FM with various animal protein sources in diets supplemented with 12% jack mackerel meal (JM) playing as feed stimulants on growth performance, feed utilization, chemical composition, amino and fatty acid profiles, and non-specific immune response of juvenile olive flounder (Paralichthys olivaceus). Two-way [3 substitution source; tuna by-product meal (TBM), chicken by-product meal (CBM), and meat meal (MM) × 2 substitution ratio; 25% and 50%] ANOVA experimental design was used. Seven experimentally formulated diets were prepared. The control (Con) diet contained 60% FM. Twenty-five and 50% of FM in the Con diet were substituted with TBM, CBM, and MM when 12% JM was included at the expense of FM, referred to as the TBM25, TBM50, CBM25, CBM50, MM25, and MM50 diets, respectively. All experimental diets were formulated to be isonitrogenous at 56.1% and isolipidic at 10.2%. Four hundred and twenty juvenile (initial weight of 18.0 g) fish were randomly distributed into 21, 50 L flow-through tanks (20 fish/tank) with three replicates of each diet. Both dietary substitution source and ratio had significant effects on weight gain, specific growth rate (SGR), and feed consumption of fish. Weight gain, SGR, and feed consumption of fish fed the Con diet was inferior to fish fed the TBM25, TBM50, and CBM25 diets, but comparable to fish fed the CBM50 and MM25 diets. However, no significant difference in feed utilization, chemical composition, amino and lipid acid profiles, and non-specific immune response of olive flounder was observed among the experimental diets. Conclusively, TBM and CBM, and MM could be used as the prominent substitutes for FM up to 50, and 25%, respectively in olive flounder feeds incorporated with JM as feed stimulants. The greatest growth performance and highest feed consumption were achieved in olive flounder fed the TBM50 diet.

3. Substitution effect of different levels of fish meal with various plant protein sources in diets supplemented with jack mackerel meal as feed stimulants on the growth, feed utilization, chemical composition, amino and fatty acid profiles, and non-specific immune response of juvenile olive flounder (Paralichthys olivaceus)

The use of plant protein sources as a substitute for fish meal (FM) in fish diet may deteriorate feed consumption by fish resulted from its reduced palatability. Therefore, an addition of feed stimulants is a very effective method as a sustainable fish culture technique to improve feed consumption by fish especially, in developing low FM-based diet. We aim to evaluate substitution effect of different levels of FM with various plant protein sources [corn gluten meal (CGM), soy protein concentrate (SPC), and corn protein concentrate (CPC)] in diets supplemented with jack mackerel meal (JM) as feed stimulants on growth of olive flounder. Two-way [2 substitution level (25 and 50%) × 3 substitution source (CGM, SPC and CPC)] ANOVA design was applied. Seven experimental diets were prepared. The control (Con) diet contained 60% FM. Twenty five and 50% FM in the Con diet were replaced with CGM, SPC, and CPC when 12% JM was included, referred to as the CGM25, CGM50, SPC25, SPC50, CPC25, and CPC50 diets, respectively. All experimental diets were isonitrogenous at 56.1% and isolipidic at 10.3%. A total of 420 juvenile fish (initial weight of 18 g) were randomly distributed into 21, 50 L flow-through tanks. All experimental diets were assigned to triplicate groups of fish. Fish were hand-fed to visual satiation twice a day, 7 days a week for 8 weeks. Weight gain, specific growth rate (SGR), and feed consumption of fish were affected by both substitution level and source. Weight gain of fish fed the Con and CGM25 diets was significantly higher than that of fish fed the CGM50, SPC50, and CPC50 diets. Feed consumption of fish was affected by both substitution level and source. Feed consumption of fish fed the Con, CGM25, SPC25, and CPC25 diets was higher than that of fish fed the CGM50, SPC50, and CPC50 diets. However, feed utilization, biochemical (proximate, amino acids, and fatty acids) composition, and non-specific immune responses of fish were not significantly affected by either substitution level or substitution source. In conclusion, FM up to 25% could be replaced with CGM, SPC, and CPC in diets without deteriorating growth performance of olive flounder when JM was included as feed stimulants