Effects of dietary protein level on growth of Cherax quadricarinatus in low salinity
[Objective]This trial was conducted to investigate the protein nutrient demand of crayfish(Cherax quadricarinatus)in low salinity(1.5‰),which would provide a theoretical basis for the development of artificial compound feed of crayfish in low salinity.[Method]Six kinds of equal energy feeds with different protein levels of 26.83％(D1),29.71％(D2),32.59％(D3),35.42％(D4),38.37％(D5)and 41.09％(D6)were prepared,and the crayfish larvae with initial weight of0.41±0.01 g were cultured for 56 days as research object.The influence of feed protein level on the growth performance,basic muscle nutrients and amino acid content of young crayfish in low salinity cul-ture environment were analyzed.[Result]The dietary protein level significantly affected the weight gain rate,specific growth rate,crude pro-tein and crude lipid contents,and amino acid content(P＜0.05,the same as below),but did not show any significant influence on survival rate,moisture and ash content of the crayfish(P＞0.05,the same as below).The weight gain rate and specific growth rate of crayfish in each group first increased and then decreased with the increase of protein level in the dietary.The weight gain rate in D3 was the highest,which was significantly higher than that in other groups.There was no significant difference in specific growth ratio among D3-D6 groups,but it was significantly higher than that in D1 and D2 groups.The crude protein content in crayfish muscle was positively correlated with the dietary pro-tein level,and the crude protein content in high protein level group(D5,D6)was significantly higher than that in other groups.On the contra-ry,the crude lipid content of crayfish muscle was negatively correlated with the dietary protein level,and the crude lipid content of crayfish muscle decreased significantly with the continuous increase of dietary protein level.Seventeen amino acids were detected in muscle,including 7 essential amino acids(EAA),2 semi-essential amino acids(HEAA)and 8 non-essential amino acids(NEAA).The total amount of amino acids with protein level of 29.71％-41.09％increased significantly with the increase of dietary protein level.[Conclusion]In the low salin-ity culture environment,considering specific growth rate,the optimum protein level of crayfish feed was 30.96％.And considering umami a-mino acid ratio(WDAA/WTAA),the optimum protein level of crayfish feed was 30.96％.
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