| In this study, we selected a representative fish species Japanese seabass (Lateolabrax japonicas) and plant protein resources soybean meal (SBM). Feeding trials were conducted to evaluate the potential and mechanism of fish meal replacement by soybean meal in Japanese seabass diet. Compared with the effect of supplementation of sulfur amino acids (includeing crystalline DL-methionine, capsulated DL-methionine and taurine), fermented SBM or gamma ray irradiation SBM as fish meal substitution in diets for Japanese seabass, investigated the main limiting fators on SBM utilization in fish meal replacement. The objective of this research was going to find effective method to improve SBM utilization in fish meal replacement. The main results are shown as follows:(1) A eight-week trial was conducted to use soybean meal (SBM) as a substitute of fish meal in diets for Japanese seabass, Lateolabrax japonicas. A control diet (C) contained 400 g/kg fish meal, and 20,40,60 and 80% of the fish meal in diet C were replaced with SBM in the other four diets (S1, S2, S3 and S4). Crystalline DL-methionine and L-lysine were added in the test diets at 3 and 2 g/kg, respectively. Initial body weight of Japanese seabass was (6.0 ± 0.1) g. The feed intake increased with decrease of fish meal level, and the feed intake was lower in fish fed diet C than in fish fed diets S1, S2, S3 and S4 (P<0.05). No significant differences were found in the final body weight (FBW) weight gain (WG) and nitrogen retention efficiency (NRE) between fish fed diets C, S1, S2 and S3 (P>0.05), while no significant differences were found in the feed conversion ratio (FCR), apparent digestibility coefficient (ADC) of dry matter and protein between fish fed diets C, S1 and S2 (P> 0.05). At the end of the trial, no significant differences were found in the condition factor (CF), viscersomatic index (VSI) and body composition (moisture, crude protein, crued lipid, ash and phosphorus) among fish fed the test diets (P>0.05). The hepatosomatic index (HSI) and intraperitoneal fat index (IFI) was lower in fish fed diet S4 than in fish fed diet C (P<0.05). Total nitrogen wastes output (TNW) increased with the decrease of fish meal level, the TNW in fish fed diet S4 was highest among the test diets (P<0.05), while no significant difference was found in the TPW among the test diets (P>0.05). The results of the present study indicate that the dietary fish meal level can be reduced to 160 g/kg if soybean meal is used as a fish meal substitute.(2) A feeding trial was conducted to evaluate the effect of dosage of crystalline DL-methionine on fish meal replacement by soybean meal in diets for Japanese seabass, Lateolabrax japonicas. A control diet (C) contained 400 g/kg fish meal. A 2 × 3 layout was used, which including three fish meal replacement level (40%,60% or 80% of the fish meal in diet C was replaced with soybean meal, fish meal content is 240,160 and 80 g/kg) and two different dosage of crystalline DL-Met supplementation (balance amino acid of the diet), supplied with 3 g/kg DL-methionine (S40, S60 and S80) or with 5,6 to 7 g/kg DL-methionine (RS40, RS60 and RS80), respectively. The 7 test diets were formulated isonitrogenous and isolipidic. Fish fingerlings weighing 6 g were fed the test diets for 8 weeks. Fish meal replacement level, Met balance and their interaction significantly affected ADCD (P< 0.05), while fish meal replacement level significantly affected FBW, WG, FCR, ADCP, NRE and TNW (P<0.05). At the same fish meal replacement level, no significant differences were found in feed intake, weight gain, FCR, NRE, PRE, CF, HSI, VSI, IFI and body composition (moisture, crude protein, crued lipid, ash and phosphorus), TNW and TPW between fish fed diets S40 and RS40 or between fish fed diets S60 and RS60 or between fish fed diets S80 and RS80 (P>0.05). At different dosage of Met balance, WG and ADCp decreased with the increase of fish meal replacement level, while FCR increased. The WG and final body weight (FBW) in fish fed diets S80 and RS80 was lower, but FCR was higher than that of in fish fed diets S40 and RS40 (P<0.05). This study indicates that the dietary fish meal level can be reduced to 160 g/kg if SBM is used as a fish meal substitute, and excessive supplementation of crystalline DL-methionine has a limited function in improving fish meal replacement by SBM in diets for Japanese seabass.(3) A 8-week feeding trial was conducted to evaluate the effects of crystalline and capsulated DL-methionine on fish meal replacement with soybean meal in diets for Japanese seabass, Lateolabrax japonicas. A reference diet (C) was formulated to contain 400 g/kg fish meal. A 2 × 4 layout was used, which including two fish meal replacement level (40% or 80% of the fish meal in diet C was replaced with SBM) and four types of DL-Met supplementation (A:Crystalline DL-Met; B:Capsulated DL-Met; C:Crystalline DL-Met+ capsule material; D:a premix containing B and C at 1:1. The 8 test diets were formulated isonitrogenous and isolipidic.5 g/kg A, 13g/kg B,13 g/kg C, or 13 g/kg D were added in diets LA, LB, LC and LD (dietary fish meal level was 240 g/kg), respectively, while 7 g/kg A,18 g/kg B,18 g/kg C or 18 g/kg D were added in diets HA, HB, HC and HD (dietary fish meal level was 80 g/kg). Initial body weight of Japanese seabass was (6.0 ± 0.1) g. Fish meal replacement level significantly affected weight gain (WG), feed intake (FI), feed conversion ratio (FCR), nitrogen retention efficiency (NRE), total nitrogen wastes output (TNW), hepatosomatic index (HSI) and proximate composition of whole fish (P<0.05); while types of DL-Met affected total phosphorus wastes output (TPW) (P <0.05). The WG and NRE decreased, while the FCR and TNW increased, with increasing of fish meal replacement level, whatever crystalline or capsulated DL-Met was added (P<0.05). At the same fish meal replacement level, no significant differences were found in the WG, FCR, NRE, CF, HSI, body composition, TNW and TPW between fish fed the diets with supplementation of A, B, C or D (P>0.05). This study indicates that dietary fish meal level for Japanese seabass can be reduced to 240 g/kg when SBM was used as a fish meal substitute, and supplentation of crystalline or capsulated DL-Met could not enhance fish meal replacement by SBM in diets for Japanese seabass.(4) Two feeding trials were conducted to evaluate if taurine supplementation can improve fish meal replacement by soybean meal (SBM) in diets for Japanese seabass, Lateolabrax japonicas. A reference diet (C) was formulated to contain 240 g/kg fish meal.In trial I,33.3% of the fish meal in diet C was replaced by SBM with 0,10 and 20 g/kg taurine supplementation (Diets H0, H10 and H20, respectively). In trial â…¡, 66.7% of the fish meal in diet C was replaced by SBM with 0,5,10,15 and 20 g/kg taurine supplementation (Diets L0, L5, L10, L15 and L20, respectively). Fish fingerlings weighing (17.2 ± 0.2) g were fed the test diets for 6 weeks. No significant differences were found in the weight gain (WG), feed intake (FI), feed conversion ratio (FCR), nitrogen retention efficiency (NRE) and body composition either between fish fed diets H0, H10 and H20 in trial â… or between fish fed diets L0, L5, L10, L15 and L20 in trial â…¡ (P> 0.05). No significant differences were found in the WG, FI, FCR, NRE and body composition between fish fed diets C, HO and H10 (trial I) or between fish fed diets C and L20 (trial â…¡) (P>0.05). However, production performance of fish fed diet C was more close to fish fed diets HO and H10, compared with fish fed diet L20. This study indicates that dietary fish meal level for Japanese seabass can be reduced to 160 g/kg when SBM was used as a fish meal substitute,5-20 g/kg taurine supplementation cannot enhance the level of fish meal replacement by SBM in the diets for Japanese seabass.(5) A feeding trial was conducted to evaluate if gamma-irradiation or fermentation could increase the inclusion level of soybean meal (SBM) in the diet of Japanese seabass Lateolabrax japonicas.A basal diet was formulated to contain 320 g/kg fish meal. In the test diets,25,50 and 75% of the fish meal in the basal diet was respectively replaced by SBM in three forms (untreated, fermented or gamma-ray irradiated). Juvenile fish (13.0 ± 0.1) g were fed with the test diets for 8 weeks. SBM treatment affected weight gain, feed intake, feed conversion ratio (FCR), phosphorus retention efficiency (PRE), phosphorus wastes output (PW), body contents of crude protein and phosphorus (P<0.05), while the level of fish meal replacement affected weight gain, apparent digestibility coefficient (ADC) of protein, FCR, nitrogen retention efficiency (NRE), PRE, nitrogen wastes output (NW), condition factor, body contents of moisture and phosphorus (P<0.05). Weight gain, ADC of protein and NRE decreased, whereas FCR and NW increased with increasing fish meal replacement by SBM, irrespective of SBM treatments. No significant differences were found in the weight gain and NRE between fish fed the basal diet and diets with 25% fish meal replacement by untreated or fermented SBM or between fish fed the basal diet and diet with 50% fish meal replacement by irradiated SBM (P>0.05). At the end of the feeding trial, no significant differences were found in condition factor, hepatosomatic index, viscerasomatic index and proximate body composition between fish fed the basal diet and diets with fish meal replaced by untreated, fermented or irradiated SBM (P>0.05). This study indicates that gamma irradiation provides a novel approach to enhance the level of fish meal replacement by SBM. Fish meal in diets for Japanese seabass can be reduced to 160 g/kg when gamma-irradiated SBM is used as a fish meal substitute.This study shows that supplementation of crystalline DL-Met, capsulated DL-Met or taurine cannot significantly improve the level offish meal replacement by SBM in diets for Japanese seabass. It reveals that the presence of anti-nutritional factors in SBM is the primary factor limiting the use of SBM as a fish meal substitute in fish diets. Gamma-irradiated SBM significantly enchanced the level of fish meal replacement by SBM in fish diets. The hypothesis was preliminary proved, and gamma-irradiation is a novel approach to improve nutritive value of SBM in fish diets. This study suggested that fish meal in diets for Japanese seabass can be reduced to 160 g/kg when SBM is used as a fish meal substitute. |
