Dietary protein requirements for three sizes of pacific white shrimp,Litopenaeus vannamei

Seven experimental diets using fish meal,soybean meal,peanut meal as the main protein sources were formulated to contain seven graded levels of protein.Three feeding trials were carried out to study the effects of different protein diets on growth and body composition of Pacific white shrimp,Litopenaeus vannamei(the weight of them were Ⅰ0.6～4g,Ⅱ4～10g,Ⅲ10～20g,respectively).The results showed that individuals with 0.6～4g weight,growth rate(WG,%) and specific growth rate(SGR,%) of shrimp fed with 42.19% and 44.38% dietary protein were significantly higher than those of shrimp fed with 32.83%～38.11% dietary protein(P0.05);however,no significant differences were found in WG and SGR of shrimp fed with 39.55% and all other dietary proteins(P0.05).Individuals with 4～10g weight,WG and SGR of shrimp fed with 38.24% dietary protein were the highest and significantly different from those of shrimp fed with 32.65%,36.78% and 39.43% dietary protein(P0.05).As for the individuals with 10～20g weight,the value of feed conversion rate(FCR) was the lowest in shrimp fed with 34.08% dietary protein,and WG and SGR of shrimp fed with 34.08% dietary protein were significantly higher than those of shrimp fed with 32.65% dietary protein(P0.05);however,no significant differences were found in WG and SGR of shrimp fed with 34.08% dietary protein and all other dietary protein except 32.65%.Dietary protein levels also affected the whole body composition of Pacific white shrimp.For testⅠ,body protein content of shrimp fed with 39.55% dietary protein was significantly higher than that of shrimp fed with 32.83%,36.52% and 42.19% dietary protein(P0.05).For testⅡ,body protein content of shrimp fed 42.07% dietary protein was significantly higher than that of shrimp fed 34.08% dietary protein(P0.05).For test Ⅲ,body protein content of shrimp fed with 36.78% dietary protein was the highest and significantly different from that of shrimp fed with 42.07% and 44.35% dietary protein(P0.05).In conclusion,the protein requirements of shrimp decreased with increasing of the shrimp weight,on the contrary,FCR increased with increasing of the shrimp weight.