Effects of the replacement of soybean meal by co-products of Chlorella on Litopenaeus vannamei growth performance,nitrogen and phosphorus loading

As the residue of defatted microalgae,Chlorella co-products were still rich in nutrient component.If the residue wasn't rationally utilized,it would not only become a waste of resources,but also cause environmental pollution.Some researchers are very conscious of the problems involved.Although they focused on protein content of the co-products,there was few detail to deal with it.This study researched on whether Chlorella co-products could replace soybean meal or fish meal in the diet of Litopenaeus vannamei. Six isonitrogenous and isoenergetic feeds were formulated and fed to white shrimp with initial weight(5.02±0.73)g for 45 days.The feeds contained 0%,6%,11%,16%,21% co-products to replace soybean meal respectively; and contained 8% co-products to replace fish meal.The six feeds were also named control,A1,A2,A3,A4 and B groups respectively.The results showed that group A3 had lower survival rate compared with control.There were no significant differences in weight gain rate and specific growth rate among group A2,A4 and control.Feed Coefficient Ratio in group A3 was the lowest compared with other groups.Protein efficiency ratio in A3 was the lowest and group B was also lower than other groups.No significant differences were found in muscle protein contents among all groups,while total phosphor contents in all replacement groups were higher than control,and group A4 was the highest.Total amino acids and total essential amino acids were first increased and then decreased,group A3 was the highest; total nonessential amino acids of control were lower than groups A1,A2 and A4.Protease activity of intestine in control was higher than other groups except group A1; but group A2 had higher lipase activity and groupA4 had lower amylase activity of intestine.In hepatopancreas,group A1 had a lower protease activity,and no significant differences among other groups.Lipase activities of all groups were higher than the control,and the A3 was the highest.Amylase activities of all groups were lower than control except A3.There were no significant differences between any groups on respiration of shrimp.The trend of nitrogen excretion was first increased and then decreased,group A3 was the highest.Phosphorus loading rates in all replacement groups was not higher than control group; nitrogen loading rate in group A3 was the higest, and that in all other replacement groups was not higher than control group.It is concluded that in view of growth performance,and nitrogen and phosphorus loading,feed containing 10% co-products to replace soybean meal which decreased to 11% from 19% may suit L.vannamei.