Qicun Zhou

Effect of dietary vitamin C on the growth performance and innate immunity of juvenile cobia (Rachycentron canadum)

This study was conducted to evaluate the effects of dietary vitamin C on growth performance, hematologic parameters and innate immune responses in juvenile cobia, Rachycentron canadum. Seven practical diets were formulated to contain 0.0 (as the basal diet), 13.6, 27.2, 54.4, 96.6, 193.4 and 386.5 mg ascorbic acid equivalent kg(-1) diet. Each diet was fed to triplicate groups of juvenile cobia with initial body weight of 5.5 g in 500-L cylindrical fiberglass tank. The results of 8 weeks feeding trial showed that typical vitamin C-deficient signs such as spinal deformation and body nigrescence were observed in the fish fed the basal diet. Fish fed the basal diet had significantly lower weight gain, specific growth rate (SGR), protein efficiency ratio (PER) and feed efficiency (FE) than those fed the diets supplemented with vitamin C, but no significant differences were observed among diets supplemented with vitamin C. However, survival rate was significantly affected by the dietary vitamin C levels, fish fed the basal diet had lower survival rate than those fed the diets supplemented with vitamin C. The ascorbic acid concentration in liver was correlated positively with the dietary vitamin C levels, however, the thiobarbituric acid reactive substances (TBARS) concentrations in liver was not significantly affected by the dietary vitamin C levels, although, fish fed the basal diet had the highest TBARS values among all treatments. The activities of serum lysozyme, superoxide dismutase (SOD), alkaline phophatase (AKP) and total immunoglobulin (Ig) were significantly influenced by the dietary vitamin C levels, fish fed the basal diet had lower lysozyme, SOD, AKP and total Ig than those fed diets supplemented with vitamin C. The serum glucose and triglyceride concentrations were significantly affected by the dietary vitamin C levels. Fish fed the basal diet had lower red blood cell and hemoglobin values than those fed the vitamin C supplemented diets. The challenge experiment with Vibrio harveyi showed that lower cumulative survival was in fish fed the unsupplemented diet, the cumulative survival were significantly increased with increase of the dietary ascorbic acid levels from 13.6 to 96.6 mg kg(-1), while the cumulative survival reached plateau when dietary ascorbic acid levels increased from 96.6 to 386.5 mg kg(-1). These results indicated that dietary vitamin C did significantly influence on growth performance and immune response of juvenile cobia.

Effects of dietary fucoidan on the blood constituents, anti-oxidation and innate immunity of juvenile yellow catfish (Pelteobagrus fulvidraco)

This experiment was conducted to investigate the effects of fucoidan on the blood constituents, anti-oxidation and innate immunity of juvenile yellow catfish, Pelteobagrus fulvidraco. Totally 420 individuals of juvenile yellow catfish were randomly allocated to 7 groups with 3 replicates per group and 20 fishes per replicate. The same experimental fish were randomly subjected to one of the following 7 treatments for 12 weeks: The basal diet was applied as control group, the experimental groups were fed on fucoidan extracted from Sargassum horneri (SF) and commodity fucoidan purchased from the market (MF), and the effective dosages were 0.05%, 0.1% and 0.2% per kilogram feed (the groups were respectively marked as SF1, SF2, SF3, MF1, MF2 and MF3). The capabilities of anti-oxidation and innate immunity were detected by the blood characters, serum enzyme activities, serum MDA content, respiratory burst activity and phagocytic index of head-kidney macrophages. Challenge test was conducted also. The results indicated that the triglyceride (TG) and total cholesterol (TC) values of the yellow catfish were significantly decreased when dietary with SF and MF, while there was no significant difference between the MF1 and the control group. Fish fed on SF and MF diets had a lower high density lipoprotein-cholesterol (HDL-C) level than those fed on basal diet except SF2 group. The low density lipoprotein-cholesterol (LDL-C) and glucose (GUL) levels of the fish were significantly decreased at the 0.2% dietary fucoidan level, and there were no significant differences between the other groups. The activities of serum superoxide dismutase (SOD) significantly increased and the contents of malondialdehyde (MDA) significantly decreased when the fish fed dietary SF and MF. The CAT activities of SF groups were higher than that of control groups, while these values were not significantly changed in MF1 and MF3 groups. The maximum of catalase (CAT) activities of the fish fed on two kind fucoidan were obtained in the SF2 and MF2 groups (fucoidan = 0.1%) respectively. The serum lysozyme (LZM) activities of the yellow catfish fed on SF and MF were significantly higher than the control ones except SF3, MF2 and MF3 group. Phagocytosis index (PI) and the respiratory burst (RB) activity of head-kidney were significantly influenced by dietary fucoidan, PI values of the fish fed on SF2, MF1 and MF2 were higher than those fed on basal diet. RB activity of the yellow catfishes were significantly increased when they were fed on fucoidan except the SF3 and MF3 groups. The challenge experiment with Aeromonas hydrophilalala revealed that the fish fed on fucoidan had no significant effect on mortality rate of the yellow catfish. These results suggested that fucoidan significantly influences the blood characters, antioxidant status, non-specific immune responses in juvenile yellow catfish.

Dietary yeast hydrolysate and brewer's yeast supplementation could enhance growth performance, innate immunity capacity and ammonia nitrogen stress resistance ability of Pacific white shrimp (Litopenaeus vannamei)

Abstract An 8‐week feeding trial was conducted to evaluate the effects of dietary yeast hydrolysate and brewers yeast supplementation on growth, immune‐related genes expression and ammonia nitrogen stress resistance of Pacific white shrimp (Litopenaeus vannamei). Three isonitrogenous and isolipidic practical diets were formulated to contain 0% (control diet), 1% yeast hydrolysate and 1% brewers yeast, respectively. 360 juvenile L. vannamei with an initial weight (0.88 ± 0.01 g) was randomly divided into 3 treatments in four replicates (30 shrimp per replicate). The results indicated that shrimp fed the diet containing 1% yeast hydrolysate had a significantly higher weight gain (WG), and specific growth rate (SGR) than that fed the control diet, and the lowest feed conversion ratio (FCR) was occurred in the 1% yeast hydrolysate supplementation group. Proximate composition in whole body and muscle among all treatments was not significantly influenced by the dietary yeast hydrolysate or brewers yeast supplementation. The challenge test with ammonia nitrogen showed that lower cumulative survival was observed in those fed the control diet, and the highest cumulative survival was occurred at shrimp fed the 1% yeast hydrolysate supplementation. Shrimp fed the control diet had higher inflammation‐related genes expression levels of tnf‐&agr; and il‐1&bgr; in the intestine than those fed the diets supplemented with 1% yeast hydrolysate or 1% brewers yeast, however, there was no significant difference in expression level of alp in intestine among all treatments. The relative expression levels of mTOR signal pathway genes (eif4ebp, eif4e1a, eif4e2 and p70s6k) were significantly up‐regulated in the shrimp fed the diets supplemented with 1% yeast hydrolysate, and the lowest gene expression levels of eif4ebp, eif4e1a, eif4e2 and p70s6k in the intestine were occurred at the control diet. The highest expression levels of the immune‐related genes (dorsal, relish, and proPO) in the intestine were observed at shrimp fed the 1% yeast hydrolysate supplementation, and the lowest expression levels of these genes were occurred at shrimp fed the control diet, however, there was no significant difference in gene expression of lysozyme among all treatments. The expression levels of penaeidin3a, crustin, proPO, and IMD in the hepatopancreas were significantly influenced by the dietary yeast hydrolysate, brewers yeast or no yeast product supplementation, shrimp fed the 1% yeast hydrolysate supplementation had higher expression levels of these genes than those fed the control diet. The present study indicated that dietary 1% yeast hydrolysate or brewers yeast supplementation could improve growth performance, enhance innate immunity, and strengthen resistance of ammonia nitrogen stress, and dietary 1% yeast hydrolysate supplementation provides better immunostimulatory effects than brewers yeast of L. vannamei. HighlightsDietary 1% yeast hydrolysate or brewer’s yeast supplementation could enhance growth performance and innate immunity capacity.Dietary 1% yeast hydrolysate or brewer’s yeast supplementation could enhance the ammonia nitrogen stress resistance ability.Dietary 1% yeast hydrolysate supplementation provides better immunostimulatory effects than brewer’s yeast.