| This study is conducted on turbot, Scophthalmus maximus L., which was a very important marine fish species in China. We explored insect meal and mixing plant protein (contain Ala-Trp/Ala-Gln) as a new source of fishmeal alternative. The experiments are presented as follows:1. A 60-day feeding trail was conducted to investigate the effects of fishmeal replacement by fermented silkworm pupae (FSP) on growth performance, blood physiology and enzymatic activities of junvile turbot (initial average weight 5.00±0.02g). Five isonitrogenous (51% CP) and isocaloric (19 MJ kg-1) practical diets were formulated to replace fishmeal at 0%,15%,30%,45%,60% levels with FSP. Each diet was randomly fed to quadruplicate groups of fish. The results showed that with increasing FSP levels, the specific growth rate (SGR) decreased and was significantly different at over 45% replacement level (P<0.05). ADC of dry matter and protein was significantly lower than control at 45% and 60% replacement level (P<0.05). Plasma protein were decreased with the level of FSP, in D3、D4、D5 were significant lower than control (P<0.05); plasma triglycerides in D4 was significant lower than control (P<0.05). In D4、D5, structure of distal intestine changed. The result indicated that FSP could have negative impact on juvenile turbot, so the replacement should not more than 30% based on the growth and healthy status.2. Effects of substituting fishmeal with different levels of defatted silkworm (Bombyx mori L.) meal (DSM) on growth performance, metabolism parameter and intestinal morphology of juvenile turbot (Scophthalmus maximus L.) were investigated over the course of a 60-day experiment. For this purpose, five isonitrogenous (51% crude protein) and isoenergetic (19 KJ/g gross energy) diets were formulated by replacing 0%(D1),15%(D2),30%(D3),45%(D4),60%(D5) fishmeal. respectively. Results of the study indicated that the final body weight, protein efficiency rate and specific growth rate were decreased with increasing DSM levels and in D5 group was significantly lower compared to D1 group (P<0.05), feed intake and survival rate of turbot had no significant differences in all treatments (P>0.05). The DSP substituted fishmeal had no influences on body moisture, crude protein, crude lipid and ash (P>0.05). In diet D5 plasma total protein was decreased than the control group while albumin was significant increased than the control group (P<0.05). Changed mucosal fold structure in distal intestine was observed in fish fed the D5 diet. Based on these parameters, the level of substitute fishmeal with DSM should not more than 45%.3. A 70-day feeding trail was conducted to investigate the effects of low fishmeal diet contain Ala-Trp on growth performance, apparent digestibility coefficient and intestinal morphology. Five isonitrogenous and isocaloric were made, fishmeal as the only protein source were control group(Dietl),4 groups Ala-trp(0.00%,0.15%, 0.25%, 0.35%) added into diets which 60% fish meal was replacement with mixing plant protein (soybean meal, corn gluten meal, peanut meal, wheat gluten meal) as Diet2, Diet3, Diet4, Diet5. To investigate the effect of 5 diets on growth, digestibility and intestinal morphology, juvenile turbot (5.00±0.02g) were fed in the system for 10 week. Results of the study indicated that the final body weight and specific growth rate were decreased accompanied by the replacing (P<0.05) and no significantly difference in low fishmeal groups. There is no significantly difference in all groups of body moisture, crude protein, crude lipid and ash (P>0.05). ADC of dry matter was significantly lower than control at all low fishmeal groups (P<0.05); while ADC of dry matter get higher and then decreased but all were lower than fishmeal treatment, in 0.15% Ala-Trp get the highest in low fishmeal treatment. Replacing fishmeal with high level mixing plant protein changed intestinal morphology:Fold height in high level mixing plant protein were lower than control (P<0.05),0.25%Ala-Trp had a highest fold height in low fishmeal groups(P<0.05); enterocytes height of 0.00%Ala-Trp significant lower than contro(P<0.05), enterocytes height of 0.25%Ala-Trp higher than control (P<0.05); microvilli height of 0.35%Ala-Trp significant lower than control (P<0.05)。... |
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