Analysis Of Meat Quality Of Blunt Snout Bream Megalobrama Amblycephala From Different Regions And Improment By Dietary Selenium Supplementation

China is a big country of aquaculture,the total annual output of aquaculture has reached more than 4,000 tons now(China Fishery Statistics Yearbook,2013).Fish has become another people's daily food except for pork on table.However,with the continuous improvement of people's quality of life,people also have higher requirements of quality of fish,people want to be able to eat more delicious,healthier and more nutritious fish.On the other hand,with the yearly increasingly amount in aquaculture and the strict control of farming land,it will inevitably result in increased stocking density,which to some extent also caused a decline in the quality of aquatic fish.In view of this,the study select the large freshwater species-blunt snout bream for the experiments and investigate muscle quality indicators of blunt snout bream from five different sources.With a view to the initial establishment of blunt snout bream muscle quality database.Besides,to investigate its effects on the growth and meat quality of blunt snout bream by regulating dietary selenium sources and yeast selenium levels.The results may provide theoretical basis for optimizing the formula for blunt snout bream,raising high-quality aquatic products that the consumer demand for.This study mainly includes three parts presented as follows:1 Analysis of meat quality of blunt snout bream from different regionsThis study aimed to investigate the meat quality of the wild-type and cultured-type of blunt snout bream(Megalobrama amblycephala)from different regions.The blunt snout bream came from Nanjing,Shanghai,Changzhou,Suqian and Wuhan,samples of Wuhan and Suqian belong to the wild-type varieties,samples of Nanjing,Shanghai,Changzhou belong to cultured-type varieties,and choosed 10 fish which weight aroud 500 g from each site.By measuring the indicators of fish weight,length,muscle proximate composition,water-holding capacity,muscle colour and muscle content,to determine more sensitive indicators of muscle of blunt snout bream in different regions.The results showed the water-holding capacity had little differences from different sources(P>0.05).However,the cultured blunt snout bream(Nanjing,Shanghai,Changzhou)had higher condition factor and muscle content,a lower moisture content and higher protein and fat contents of muscle compared to the wild blunt snout bream(Suqian,Wuhan),which had a more ruddy muscle colour(P<0.05).Fish condition factor,proximate composition of muscle and muscle colour can be more clearly reflected the muscle quality differences in blunt snout bream from different sources,which can be used as blunt snout bream muscle quality evaluation based on.2 Effects of dietary selenium on the growth,selenium status and antioxidant activities of blunt snout breamThis study was conducted to evaluate the effects of dietary selenium on the growth,selenium status and antioxidant activities of blunt snout bream(average initial weight:68.61±0.98 g).Fish were fed by seven isonitrogenous and isoenergenic diets.Sodium selenite(Na2SeO3)and selenium nanoparticle(Nano-Se)were respectively added to the basal diet at 0.2 mg Se/kg dry diet.Selenium yeast(Se-yeast)was added to the basal diet at 0.1,0.2,0.4 and 0.8 mg Se/kg dry diet,respectively.The basal diet was without Se supplementation as the control treatment.The whole experimental trial was lasted for 8 weeks.The results indicated that groups of 0.2,0.4 mg/kg Se-yeast had significantly higher weight gain and Nano-Se,0.2,0.4 mg/kg Se-yeast had significantly lower feed conversation ratio than that of control group(P<0.05).The Se concentrations of whole body,muscle and liver linearly increased with increase of dietary Se-yeast levels.There were no differences in antioxidant activities of three selenium sources at the level of 0.2 mg Se/kg(P>0.05).Group of 0.4 mg/kg Se-yeast significantly increased activities of catalase and glutathione peroxidase and significantly decreased activity of glutathione reductase and content of malondialdehyde(P<0.05).Based on weight gain,the optimal dietary Se requirement of blunt snout bream(weight:70-210 g)is estimated to be 0.43 mg/kg.3 Effects of dietary selenium on meat quality of blunt snout breamThis study was conducted to evaluate the effects of selenium on meat quality of blunt snout bream.The experimental design was the same as study one.The results indicated that there were no significant differences in proximate composition and amino acids of muscle and muscle content(P>0.05).Muscle colour of Nano-Se,0.2,0.4 mg/kg Se-yeast groups,the water-holding capacity of 0.4,0.8 mg/kg Se-yeast groups showed significant differences from those of control group(P<0.05).In conclusion,the cultured blunt snout bream had a higher condition factor and higher content of protein and fatty of muscle than the wild blunt snout bream,which had a more ruddy colour.Se-yeast and Nano-Se have higher bioavailability and better growth performance than Na2SeO3 at 0.2 mg Se/kg level for blunt snout bream.Nano-Se has some effect to stabilize the muscle colour of this species.Se-yeast improves growth,increases the Se concentration of muscle,increases antioxidant activities and enhances the meat quality of blunt snout bream.Based on weight gain,the optimal dietary Se requirement of blunt snout bream(weight:70-210 g)is estimated to be 0.43 mg/kg.