Effect of Dietary Cornstarch Levels on Growth Performance,Digestibility,and Microscopic Structure in Penaeus vannamei Reared in Brackish Water

摘要

The ability of Penaeus vannamei(initial mean weight:0.96±0.02g) to utilize different levels of cornstarch was examined in terms of growth indices,body composition,digestibility and microscopic structure of the hapetopancreas.Six isonitrogenous semipurified diets were fed to satiation to shrimp in triplicate tanks(30 shrimps tank-1) connected to a natural brackish water(6-8 g L-1) recirculating system for 8 weeks.Diets contained 10,15,20,25,30,and 35% cornstarch.Weight gain(WG),survival rate,and feed conversion rate(FCR) were significantly(P>0.05) affected by dietary cornstarch levels.The highest WG(453.6%) and lowest FCR(1.38) were observed in shrimp fed the diet with the 15% cornstarch.Survival rate(96.7%),however,was highest in shrimp fed the diet with 10% cornstarch,which was some 30% higher than the treatment group with the lowest survival rate(66.7%) in shrimp fed diets with 25% cornstarch.Weight gain,survival rate,and FCR were significantly(P<0.05) lower for shrimp fed diets with 25-35% cornstarch than the other treatment groups.Body lipid tended to be higher in shrimp fed diets with higher cornstarch levels.The apparent digestibility coefficient of dry matter and crude fat increased with increasing levels of dietary cornstarch.Furthermore,the shrimp fed 10 to 35% dietary cornstarch exhibited some histological changes.Results in this study suggested that the optimum dietary cornstarch level is between 10 and 20% when the diets contain 38% protein.