Feeding trials were conducted to determine the dietary level of yeast extract (YE) for replacing dietary fish meal for evaluating whether yeast extract was superior to intact yeast as an alternative protein source for shrimp Litopenaeus vannamei. The basal diet (control, D0, containing 25% fish meal), was compared with five isonitrogenous and isoenergetic experimental diets [replacing 15% (D15), 30% (D30), 45% (D45), 60% (D60) or 100% (D100) of the fish meal in the basal diet with IYE]. The digestibility, growth and muscle composition of the shrimp were measured. The results showed that all replacement treatments displayed higher apparent digestibility of crude protein than did the control. The trypsinase activity in shrimp hepatopancreas increased significantly, whereas lipase activity decreased as the amount of dietary YE increased. The shrimp treated with D30 diet displayed the highest amylase activity in hepatopancreas. There was no significant difference in the weight gain (WG) and survival of shrimp between the control and the YE replacement treatments. Feed conversion ratio (FCR) increased as the dietary YE increased, and the FCRs of the D60 and the D100 treatments were significantly higher than that of the control (P<0.05). The growth performance among the treatments was closely related to the similarity of the essential amino acids in the diets. There was no significant difference in muscle composition of the shrimp between control and other treatments. In conclusion, up to approximately 45% of the fish meal in shrimp diet can be replaced by yeast extract in the presence of supplemental fish oil, phosphorus and calcium.

Toll receptor is a kind of transmembrane protein. The extracellular domain of Toll receptor can recognize the highly conserved components of pathogens, termed pathogen-associated molecular patterns (PAMPs), which is only expressed on pathogen microbe. The signal on pathogen invasion is transmitted into cell by Toll receptor and then induce cascades on production of immune effectors and immune reactions. Toll receptor is vital for innate immunity of organism. The existence of Toll receptor has been verified in some kinds of shrimp. But the application of Toll receptor in nutrition-immunity study of shrimp is scarce. This paper reviews the signal pathway of Toll and research advance on prawn Toll. The application of Toll receptor in nutrition-immunity assessing on prawn is also elucidated. The variation on expression of Toll receptor gene may reflect the sensitivity of organism to invading pathogen. Expression of Toll receptor gene should be a valuable parameter for assaying nutrition-immunity of shrimp. However, more research should be conducted in future to interpret the effects of dietary nutrients on expression of Toll receptor gene. Whether expression of Toll receptor gene of shrimp could reflect the immunological function of the diet should also be studied.

The basal diet(A) contains 25% fish meal as control,and four isonitrogenous isoenergic yeast extract experiment diets,which substituted 15%(B),30%(C),45%(D) and 60%(E) fish meal in basal diet,were fed to the Litopenaeus vannamei(7.50±0.13) g respectively for 42 d,then superoxide dismutase(SOD) activity and lysozyme(LSZ) activity in haemolymph and the expressions of lysozyme mRNA and Toll receptor mRNA in gill were detected.The shrimp were also challenged with Vibrio alginolyticus.The results showed that: LSZ activity in haemolymph in 15% group was significantly higher than that of control(P0.05).There was no significant difference of SOD activity in haemolymph,the expressions of lysozyme mRNA and Toll Receptor mRNA in gill between alternative groups and control group(P0.05).The cumulative mortality of 60% group at 24 h and 48 h was significant higher than that of control(P0.05),and there was no significant difference of cumulative mortality between alternative groups and control group at 72 h and 96 h(P0.05).It is therefore suggested that yeast extract can replace 45% fish meal of the diets without affecting immunity and vibrio-resistant ability of the shrimp.

Experiments were conducted to determine copper accumulation,SOD and lysozyme activities,immune-related genes(Toll receptor mRNA and Lysozyme mRNA) expression level and Vibrio-resistant ability of white shrimp Litopenaeus vannamei fed the diet with different copper levels(via adding copper methionine 0,30 and 50 mg Cu/kg) for 7d,14d and 21d,respectively.The results indicated that the copper content in hepatopancreas of shrimp significantly increased(P0.05) with increasing dietary copper and feeding time.Copper content in muscle was always significantly lower than that in hepatopancreas(P0.05).There was no significant difference in lysozyme activities in hepatopancreas,muscle and haemolymph of the shrimp among different copper treatments(P0.05),although SOD activity of the shrimp was affected by dietary copper level as well as feeding time.The SOD activities in muscle,haemplymph and hepatopancreas of the shrimp treated with 30 mg Cu/kg diet for 21d were significantly higher than those of the shrimp treated with 50 mg Cu/ kg and 0 mg Cu/kg diets.The dietary copper level did not affect the lysozyme mRNA expression level in shrimp’s gills,but it significantly affected the Toll receptor mRNA expression level in shrimp’s gills(P0.05).The Toll receptor mRNA expression level in shrimp’s gills increased significantly(P0.05) with an increasing dietary copper for 7d(P0.05).While the shrimp treated with 30 mg Cu/kg diet showed the highest Toll receptor mRNA expression level in gills for 14d and 21d.The shrimp treated with 50 mg Cu/kg diet for 7d or with 30 mg Cu/kg diet for 14d displayed the largest half lethal time and complete lethal time when the shrimp were artificially infected with Vibrio alginolyticus.It is therefore suggested that dietary copper level affected not only the accumulation of copper in shrimp tissues,but also the SOD activity and Toll receptor mRNA expression level of the shrimp and finally affected the Vibrio resistance of the shrimp.

The relative expression levels of Toll receptor and lysozyme mRNA in different tissues（haemolymph,gill,muscle and hepatopancreas） of the white shrimp,Litopenaeus vannamei,were quantitatively detected with real-time PCR technology.The results indicated that the expressions of Toll receptor and lysozyme mRNA among tissues were significantly different.The relative expression of Toll receptor mRNA in haemolymph was significantly higher than that in gill as well as in muscle and hepatopancreas,and the relative expression of Toll receptor mRNA in gill was significantly higher than those in muscle and hepatopancreas.The relative expressions of lysozyme mRNA in haemolymph and in gill were significantly higher than those in muscle and hepatopancreas.While there was no significant difference between relative expressions of lysozyme mRNA in haemolypha and gill.There was no significant difference between the variation coefficients of Toll receptor and lysozyme mRNA expressions in haemolymph and in gill.It is therefore suggested that haemplymph and gill were the suitable material for assays of Toll receptor and lysozyme mRNA expression levels for L.vannamei.

Experiments were conducted to study the effects of dietary zinc supplementation on the immune gene expression and immunity and disease-resistant ability of white shrimp(Litopenaeus vannamei).The shrimp were fed with 3 zinc methionine diets(supplemented at 0,50,150 mg Zn/kg diet respectively)respectively for 14 days.Then the expressions of Toll Receptor mRNA and lysozyme mRNA in gill and superoxide dismutase(SOD)activity and lysozyme(LSZ)activity in hepatopancreas,muscle and haemolymph were assayed respectively.The shrimp treated with different zinc diets were also challenged with Vibrio alginolyticus.The results showed that the zinc levels in hepatopancreas and muscle of shrimp significantly increased(P0.05)as the dietary zinc increased.While the hepatopancreas accumulated more zinc than muscle.Compared to those of the shrimp in 0 mg Zn/kg and 150 mg Zn/kg treatments,the expressions of Toll receptor mRNA and lysozyme mRNA in gill of the shrimp in 50 mg Zn/kg treatment were significantly up-regulated.The lysozyme activities in muscle,hepatopancreas and haemolymph of the shrimp in 50 mg Zn/kg treatment were significantly higher than those in 0 mg Zn/kg treatment(P0.05).The SOD activities in hepatopancreas and haemolymph of the shrimp in 50 mg Zn/kg and 150 mg Zn/kg treatments were also higher than those in 0 mg Zn/kg treatments(P0.05).While the SOD activity in muscle of the shrimp treated with 150 mg Zn/kg was significantly higher than those treated with 0 mg Zn/kg and 50 mg Zn/kg respectively.The half lethal time and complete lethal time for the shrimp in 50 mg Zn/kg treatment were longer than those in 0 mg Zn/kg and 150 mg Zn/kg treatments after being challenged with V.alginolyticus.It is therefore suggested that compared to those in 0 mg Zn/kg and 150 mg Zn/kg treatments,the shrimp fed the diets added 50 mg Zn/kg(the content of zinc in diet was 73.25 mg Zn/kg)had improved immunity and Vibrio-resistant ability.

The effects of corn gluten meal(CGM) as a partial replacement of fish meal in diet on the growth and muscle composition of Macrobrachium nipponensis were studied.The experiment diets contained a gradient of CGM such as 0%(the control),3%,6%,9%,12% and 12%+0.1%MHA-Ga respectively.All diets were fed to the shrimp triplicately.In the first phase of the experiment,diets were fed to juvenile shrimp(initial body weight of 0.12±0.04 g) for 30 days,and in the second phase diets were fed to juvenile shrimp(initial body weight of 0.23±0.12 g) for 23 days.Growth,survival rate and the muscle composition of M.nipponensis were determined.The results indicated that there was no significantly difference in relative growth rate and survival rate among the treatments(P0.05)although there was a tendency of declining relative growth rate with the increment of the partial replacement.The nutrition assays of the shrimp muscle indicated that there were no significant effects of the partial replacement on water content,total lipid,crude ash,total amino acid(TAA)and total essential amino acid(TEAA)of the shrimp muscle(P0.05).The poly-unsaturated fatty acid and DHA+EPA proportion in total fatty acid profiles of the muscle obviously decreased as the amount of CGM in diet was more than 9.0%.