Effects Of β-glucan On Growth Performance And Immunity Function Of Yellow Catfish, Pelteobagrus Fulvidraco

In this study, a feeding and an injection trial were undertaken to investigate the effects of β-glucan on growth performance, body composition, serum biochemical indices, immunity function, oxidation resistance and resistance against Aeromonas hydrophila infection of yellow catfish, Pelteobagrus fulvidraco. The study comprised of three parts. 1. Effects of dietary β-glucan on growth performance, body composition and serum biochemical indices of juvenile yellow catfish, Pelteobagrus fulvidracoA total of 720 juvenile yellow catfish with an initial body weight of(1.53±0.04) g were randomly divided into 7 groups, including feeding with basal diet as control group(G0), continuous feeding with diets of different levels of β-glucan(SG200, SG600 and SG1000), and interval feeding with diets of different levels of β-glucan for 7 days followed by the basal diet for 7 days(IG200, IG600 and IG1000). The feeding trail lasted for 42 d. The results showed that there were no significant differences(P>0.05) in weight gain rate(WGR), survival rate(SR), feed coefficient(FC) and protein efficiency ratio(PER) among all the groups, but the fish fed diets supplemented with β-glucan showed higher WGR and PER than the control group, also the fish continuously fed diet supplemented with β-glucan showed higher WGR than intervally fed with diet supplemented with the same level of β-glucan. Compared with the control group, hepatosomatic index(HSI) in IG1000 was significantly lowered(P<0.05). Compared with the control group, the content of crude protein, crude lipid and ash in the other six groups increased to some extent, but no significant difference was observed(P>0.05). There was no significant difference in serum biochemical indices among all the groups(P>0.05). However, compared with the control group, the content of globulin and total protein in SG1000 and IG600 was higher and the activities of glutamic oxalacetic transaminase(GOT) and glutamic pyruvic transaminase(GPT) were lower(P>0.05). In conclusion, using either continuous or interval feeding strategy, addition of 200, 600 and 1000 mg/kg β-glucan to diets had no significant effects on growth performance, body composition and serum biochemical indices of juvenile yellow catfish, except that HSI of interval feeding 1000 mg/kg was significantly lower than the control group.2. Effects of dietary β-glucan on serum immunity, antioxidant indices, kidney cytokines and resistance against Aeromonas hydrophila of juvenile yellow catfish, Pseudobagrus fulvidracoAfter the 42-day feeding trial described above, samples were taken and serum immunity, oxidant indices and kidney cytokines were measured. 40 fish from each group were selected and challenged with Aeromonas hydrophila for 96 h. The results showed that compared with G0, serum lysozyme(LZM) activities in all supplemented groups were reduced but the differences were not significant(P>0.05), serum acid phosphatase(ACP) and alkaline phosphatase(AKP) activities in IG200 were increased and reduced significantly(P<0.05). There were no significant differences in nitric oxide synthase(NOS) activities among all the groups(P>0.05). Anti-O2- in G0 was significantly higher than that in IG600(P<0.05) but not significantly different with other groups(P>0.05). No significant differences were found in nitric oxide synthase(NOS) activities, superoxide dismutase(SOD) activities, total antioxidant capacity(T-AOC) and malondialdehyde(MDA) content among all the groups(P>0.05), but T-AOC in G0 was the highest. In IG1000, the content of kidney interleukin-1β(IL-1β), interleukin-6(IL-6) and tumor necrosis factor(TNF-α) was significantly higher(P<0.05) than that in G0 and no significant differences were found among other groups(P>0.05). After Aeromonas hydrophila infection for 96 h, the accumulative mortality rate(AMR) was from 35% to 46% and no significant difference was found among all groups(P>0.05). It is concluded that under the conditions of the present experiment, using either continuous or interval strategy, addition of 200, 600 and 1000 mg/kg β-glucan to diets had no significant effects on serum immunity, antioxidant indices and resistance against Aeromonas hydrophila in juvenile yellow catfish, however, interval feeding with diets supplemented with 1000 mg/kg β-glucan could significantly improve the levels of IL-1β, IL-6 and TNF-α in kidney. 3. Effects of intraperitoneal injection of β-glucan on serum immunity and antioxidant-related indices and resistance against Aeromonas hydrophila of yellow catfish, Pseudobagrus fulvidraco500 yellow catfish with an initial body weight of(60.0±5.0) g were randomly divided into 5 groups, and intraperitoneally injected with a dosage of 0, 5, 10, 20 and 40 mg/kg β-glucan suspension respectively, named as G0, G5, G10, G20 and G40. On the 2nd, 4th and 6th day after injection, serum samples were collected and immune and antioxidation-related indices were analyzed. On the 7th day, 60 fish from each group were randomly selected and challenged with Aeromonas hydrophila by intraperitoneal injection for 48 h. The results showed that on the 2nd day, IgM content in 5 mg/kg group was significantly higher than other groups. On the 4th day, IgM content in 10 mg/kg group was significantly higher than 5 and 40 mg/kg groups. On the 6th day, IgM content in 10 mg/kg group showed the highest value, significantly higher than the control and other injected groups(P<0.05). On the 2nd and 4th day, SOD activity in all the groups was not different(P>0.05). On the 6th day, SOD activity in the injected groups was significantly higher than the control group(P<0.05). On the 2nd day, MDA content in all the groups was not different(P>0.05). On the 4th and 6th day, MDA content in 20 and 40 mg/kg groups was significantly higher than that in the control(P<0.05). On the 2nd day, serum IL-6 content in 5 mg/kg group was significantly higher than that in other groups(P<0.05). On the 4th day, serum IL-6 content in 10 and 20 mg/kg group was significantly higher than that in in other groups(P<0.05). On the 6th day, serum IL-6 content in 10 mg/kg was highest, however, no significant difference was found(P>0.05). Compared to the control group, the AMR in the β-glucan-injected groups was reduced and significantly lowered(P<0.05) in 10 mg/kg group. In conclusion, intraperitoneal injection of β-glucan could promote the immune and antioxidant-related indices, and improve the resistance against Aeromonas hydrophila infection of yellow catfish.