Junming Cao

Effects of replacement of fish meal with housefly maggot meal on growth performance,antioxidant and non-specific immune indexes of juvenile Litopenaeus vannamei

This study was conducted to evaluate the effects of replacement of fish meal by housefly maggot meal(HMM) on growth performance,antioxidant and non-specific immune indexes of juvenile white shrimp(Litopenaeus vannamei).Six isonitrogenous and isoenergetic diets were formulated with 0,20%,40%,60%,80% and 100% replacement of fish meal with HMM on a protein basis.960 juvenile shrimp with an average body weight of(0.56±0.03) g were randomly assigned to 6 groups.The shrimp were fed six diets respectively,named G0,G20,G40,G60,G80 and G100.After 45 d feeding,there was no significant difference in WGR(weight gain rate) from G20 to G60,while it was significantly decreased in G80 and G100.SGR(specific growth rate) of shrimp were significantly lower than that of the control group except for G40(P0.05).FI(feed intake)in G100 was significantly lower than other groups(P0.05).Compared with the control group,there was no significant difference in FCR(feed conversion ratio),PER(protein efficiency ratio),PPV(productive protein value),HSI(hepotosomatic index) when the replacement levels were no more than 60%,while FCR,HSI were significantly increased and PER,PPV were significantly decreased with increasing HMM replacement ration.CF(condition factor) and SR(survival rate) in HMM groups were higher than those in the control group to some extent.With HMM increasing,crude protein,calcium and total phosphorus content increased significantly and crude lipid content decreased(P0.05),while dry matter and ash content were not significantly different(P0.05).No significant difference was found among all the treatments in serum and hepatopancreas SOD(superoxide dismutase) activity,and serum MDA(malondialdehyde) content(P0.05),and MDA content in G80 and G100 was significantly higher than that of the control group(P0.05).Serum PO(phenoloxidase) activity tended to increase first and then decrease,the highest value was observed in G20(P0.05).Hepatopancreas AKP(alkaline phosphatase) activity decreased significantly with HMM increasing(P0.05).In all the treatments,no significant difference was observed in serum THC(total haemocyte count),NO(nitric oxide) content,AKP activity and hepatopancreas PO activity and NO content(P0.05).

Effects of dietary arginine levels on growth performance, body composition, serum biochemical indices and resistance ability against ammonia-nitrogen stress in juvenile yellow catfish (Pelteobagrus fulvidraco)

This experiment was conducted to investigate the effects of dietary arginine levels on growth performance, body composition, serum biochemical indices and resistance ability against ammonia-nitrogen stress in juvenile yellow catfish (Pelteobagrus fulvidraco). Five isonitrogenous and isolipidic diets (42% protein and 9% lipid) were formulated to contain graded levels of arginine (2.44%, 2.64%, 2.81%, 3.01% and 3.23% of diet), by supplementing L-Arginine HCl. Seven hundred juvenile yellow catfish with an initial average body weight of 1.13 ± 0.02 g were randomly divided into 5 groups with 4 replicates of 35 fish each and each group was fed one of the diets. After 56 d feeding, fish were exposed to 100 mg/L of ammonia-nitrogen for 72 h. The results showed that weight gain (WG) and specific growth rate (SGR) in 2.64% and 2.81% groups were significantly higher than those in 3.23% group (P < 0.05). The feed conversation ratio (FCR) in 2.64%, 2.81% and 3.01% groups was significantly decreased when compared with 3.23% group. The protein efficiency ratio (PER) in 2.64% group was significantly higher than that in 2.44% and 3.23% groups (P < 0.05). The condition factor (CF) of fish was significantly higher in 2.81% group than that in 2.44% group (P < 0.05). Dietary arginine levels had no significant effect on hepatosomatic index (HSI), viscerosomatic index (VSI), and whole-body dry matter, crude protein, crude lipid, ash contents, as well as serum total protein (TP), triglyceride (TG), glucose (GLU), urea nitrogen (UN) contents and aspartate aminotransferase (AST), alanine aminotransferase (ALT) activities (P > 0.05). After the fish were challenged to ammonia-nitrogen for 72 h, their cumulative mortality rate in 2.81% group was significantly lower than that in 2.44% group (P < 0.05). The results suggested that dietary arginine level at 2.81% could optimize anti-ammonia-nitrogen stress ability of juvenile yellow catfish and a level of 3.23% arginine seemed to depress the growth performance of fish and decreased their tolerance to the ammonia-nitrogen stress under current study. A quadratic regression analysis based on WG indicated that the optimal dietary arginine requirement of juvenile yellow catfish was estimated to be 2.74% of the diet (6.45% of dietary protein) under current culture conditions.