Studies On The Tolerance Of Large Yellow Croaker (Larimichthys Croceus) To Dietary Soybean Meal And Canola Meal

In the studies, feeding trials were conducted to evaluate the effect of replacementof fish meal with two plant protein source source such as soybean meal and canola mealon growth performance, serum biochemical indices and digestive tract histology for thelarge yellow croaker. Furthermore, another feeding experiment was conducted to analyzethe effects of dietary nucleotides on growth performance, anti-oxidative capacities andintestinal morphology of juvenile large yellow croaker. Results of the experiment arepresented as follows:1A feeding trail was conducted to investigate the effect of replacement of fishmeal with soybean meal on growth performance, serum biochemical indices anddigestive tract histology for th large yellow croaker (initial weight:135.38±1.02g). Fivediets were formulated by replacing0%,15%,30%,60%,100%fishmeal with soybeanmeal (SBM).Results showed that the survival rate (SR), specific growth rate (SGR) and weightgrain rate (WGR) of the animals were significantly influenced by dietary soybean meallevels (P<0.05). The lowest value of three parameters was found in the treatment with100%dietary soybean meal.The body composition were significantly affected by dietarysoybean meal levels (P<0.05). The hepatosomatic index, viscerosomatic index andCondition factor of fish fed the diets with600g/kg of soybean meal were significantlylower than the control group (P<0.05). There was no significant difference in Glucose(GLU) of the serum (P>0.05). Dietary soybean meal significantly affectedthetriglycerides (TG) and total cholesterol (TC) in serum (P<0.05). Values of TG andTCincreased first, and then declined as the dietary soybean meal levels increased.Thelowest value of these two parameters was found in the treatment with600g/kg of dietarysoybean meal. The histological study showed that ultrastructure of the liver and theintestinal were abnormal. Serious vacuolization in liver, significant thinning of theintestinal wall and the severe mechanical damage of intestinal villi were found inthe15%-100%dietary soybean meal. In conclusion, replacement of fish meal by SBM at the level of60%can be considered as an optimum replacement level under the presentexperimental condition.2A feeding trail was conducted to investigate the effect of replacement of fish mealwith Canola meal on growth performance, serum biochemical indices and digestive tracthistology for the large yellow croaker(initial weight:135.38±1.02g）.Five diets wereformulated by replacing0%,15%,30%,60%,100%fishmeal with Canola meal (CM).Results showed that the survival rate (SR) of the animals was no significantlyinfluenced by dietary CM levels (P>0.05). Specific growth rate (SGR) and weight grainrate (WGR) of fish fed the diets with600g/kg of CM were significantly lower than thosein the other groups. Moisture and Crude lipid of the fish were no significantly influencedby dietary CM levels (P>0.05), but the crude protein and ash were significantlyinfluenced by dietary CM levels (P<0.05). The hepatosomatic index (HSI),viscerosomatic index (VSI), triglycerides (TG) and total cholesterol (TC) were nosignificantly influenced by dietary CM levels (P>0.05). As the dietary Canola meal levelsincreased, condition factor of the fish was significantly declined (P<0.05); glucose (GLU)in serum was significantly increased (P<0.05). The histological study showed thatultrastructure of the liver and the intestinal were abnormal. Serious vacuolization in liver,significant thinning of the intestinal wall and the severe mechanical damage of intestinalvilli were found in15%-100%dietary canola meal. In conclusion, replacement of fishmeal by CM at the level of30%can be considered as an optimum replacement levelunder the present experimental condition.3．The present study was conducted to analyze the effects of dietary nucleotides ongrowth performance, anti-oxidative capacities and intestinal morphology of juvenile largeyellow croaker (initial weight:7.71±0.02g). Two control diets were set. They were highfishmeal (FM,45.0%) supplemented diet and low fishmeal (N0,31.5%) supplementeddiet, respectively. Based on the latter, five graded levels of nucleotides were added. Theywere75,150,300,600and1000mg/kg, respectively. After the9-week growth trial,results showed that survival rate, feed efficiency and body composition of the animalswere no significantly influenced by dietary nucleotides levels (P>0.05). Weight gain rate(WGR) of fish fed the diets with300mg/kg or600mg/kg of nucleotides weresignificantly higher than those in the other groups (P<0.05). Dietary nucleotides significantly affected the total anti-oxidative capacity (T-AOC) and superoxide dismutase(SOD) activity in serum (P<0.05). Values of T-AOC and SOD increased fist, and thendeclined as the dietary nucleotides levels increased. The highest value of these twoparameters was found in the treatment with300mg/kg of dietary nucleotides. Dietarynucleotide significantly increased microvillus height (HMV) and the thickness of themuscular layer (TML) in the proximal intestine (P<0.05). The HMV in intestine of fishfed diet with300mg/kg of nucleotides was higher than that in the control group. TheTML in intestine of fish fed diet with600mg/kg of nucleotides was higher than that inthe control group. There was no significant difference in folds height (HF) of intestinalamong the all groups (P>0.05). In conclusion, dietary nucleotides can improve thegrowth of the large yellow croaker. Meanwhile, it can also increase the anti-oxidativecapacity and improve the intestinal morphology. Based on the data of WGR, thebroken-line analysis showed that the optimal level of dietary nucleotides was194.91mg/kg.