| The present study was to investigate the effects of dietary carbohydrate/lipid(CHO:L)ratios on growth performance,feed utilization,non-specific immune,hepatic inflammatory injury hepatic antioxidant capacity,and liver histology of Pseudobagrus ussuriensis in order to determine the optimum level of CHO:L ratio in the diet for Pseudobagrus ussuriensis.The results of the study could provide the technical support for optimizing the diets,industrial development for Pseudobagrus ussuriensis.The results of the study are presented as follows:The effects of dietary CHO:L ratios for Pseudobagrus ussuriensis(initial body average weight 5.01 g)were evaluated in an 8-week feeding trial.Dextrin was used as the carbohydrate source and soybean oil was used as the lipid source.Triplicate groups(25 fish per treatment)of Pseudobagrus ussuriensis were fed one of six isonitrogenous and isoenergetic diets which were formulated to contain various CHO:L ratios from 0.89(C1(0.89)),1.38(C2(1.38)),2.02(C3(2.02)),2.84(C4(2.84)),4.11(C5(4.11))and 7.02(C6(7.02)),respectively.The results showed that final body weight(FBW),weight gain(WG),specific growth rate(SGR),feed intake(FI),feed efficiency(FE)and protein efficiency ratio(PER)reached to the maximum level at dietary CHO:L ratio of 2.02.Fish fed C3(2.02)diet had significantly higher the protein content of whole body than the fish fed C2(1.38)diet.There were no significant differences for moisture,lipid and ash contents(P>0.05).The muscle protein content of fish fed C3(2.02)diet was significantly higher than the other experiment group(P<0.05).The lipid content of muscle increased with increasing dietary CHO:L ratio,and then decreased.The muscle lipid content of fish fed C6(7.02)diet was significantly lower than the other experiment group(P<0.05).No significant difference was observed in the muscle moisture and ash contents among the groups(P>0.05).The alpha-amylase activity of fish fed C3(2.02)diet was higher than the C2(1.38)group and reached to the maximum level.The lipase activity decreased with increasing dietary CHO:L ratio.The lipase activity of fish fed C6(7.02)diet was significantly lower than the C1(0.89),C2(1.38)and C3(2.02)groups(P<0.05).No significant difference was observed in pepsin activity among the groups(P>0.05).The hepatic IGF-I expression level firstly significantly increased(P<0.05)and reached to the maximum level at dietary CHO:L ratio of 2.02,and then significantly decreased with increasing CHO:L ratio from 2.84 to 7.02(P<0.05).The plasma lysozyme activity,respiratory burst activity(RBA)and complement 3 increased with increasing the dietary CHO:L ratio,and then decreased.The plasma lysozyme activity of fish fed C3(2.02)diet was higher than the C1(0.89),C2(1.38),C5(4.11)and C6(7.02)groups(P<0.05).The RBA of fish fed C3(2.02)diet was higher than the C1(0.89),C5(4.11)and C6(7.02)groups(P<0.05).The plasma complement 3 of fish fed C3(2.02)diet was higher than the other groups(P<0.05),but remained unaffected significantly when compared with the C1(0.89)group(P>0.05).No significant differences were observed among the treatments in plasma AKP activity and complement 4 content(P>0.05).The hepatic tumour necrosis factor α(TNF-α),interleukin 1β(IL-1β)and heat shock protein 70(HSP-70)gene expression level all firstly decreased and reached to the minimum level at dietary CHO:L ratio of 2.02,and then increased with increasing CHO:L ratio from 2.84 to 7.02.Conversely,the hepatic interleukin-10(IL-10)gene expression level firstly increased and reached to the maximum level at dietary CHO:L ratio of 2.02,and then decreased with increasing CHO:L ratio from 2.84 to 7.02.Fish fed C2(1.38)diet had significantly lower hepatic catalase(CAT)activity than the C3(2.02)group(P<0.05).Significantly higher superoxide dismutase(SOD)activity was found in C3(2.02)group compared with the C4(2.84),C5(4.11)and C6(7.02)groups(P<0.05).The highest total antioxidant capacity(T-AOC)was found in fish fed C3(2.02)diet.The malondialdehyde content(MDA)decreased with increasing dietary CHO:L ratios.Histological observation showed that Fish fed C1(0.89)and C2(1.38)diets could cause vacuolation and partial nuclei migration of liver cells,and fish fed C5(4.11)and C6(7.02)diets could cause hypertrophy of the hepatic cells,markedly vacuolation and nuclei migration of liver cells.In conclusion,dietary optimal CHO:L ratio is 2.02 with providing the best growth performance,physiological function and health status for Pseudobagrus ussuriensis. |
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