Effects of different dietary protein content on growth and protease activity of Eriocheir sinensis larvae

This paper studied the effects of dietary protein content on growth and protease activity of Eriocheir sinensis larvae. The results suggest that if E. sinensis larvae were fed diets of different protein content, their survival, metamorphic rate and weight gain all changed significantly (P<0.05), but the amount of change differed. Larvae survival was highest from Z3 to Z4, and the variation in weight gain of each treatment group declined gradually as the larvae developed. During the 20 h post-metamorphosis of every larval stage, the protease activity increased at Z1, Z2, Z3 and M, and declined at Z4 and Z5, meanwhile the protease activity of larvae was influenced significantly by the protein content of the diets (P<0.05). In addition, 4 h after the larvae were fed, the protease activity at each larval stage changed corresponding to dietary protein content, while 12 h later the changes tended to be stable. Considering the growth of larvae and the flexibility of protease, it can be concluded that the appropriate protein requirements at Z1, Z2, Z3, Z4, Z5 and M were, respectively, 45%, 45%, 50%, 45%, 45% and 40%.