Effect Of Iron On Functions Of Digestion, Absorption, Immune And Antioxidative Of Juvenile Jian Carp (Cyprinus Carpio Var. Jian)

The experiment was to investigate the effect of dietary iron supplement on growth performance,functions of digestion,absorption,immune and antioxidative ability.In 60 days feeding trial,a total of 1050 juvenile Jian carp(Cyprinus carpio var.Jian)(11.35±0.02 g,mean±SD) were fed diets containing seven graded levels of iron:40,70,100,130, 160,200,250 mg kg^-1(53.9,90.0,115.6,146.1,176.0,215.8 and 266.0 mg iron kg^-1 diet). After the growth trial,30 fish in each treatment were randomly assigned to a challenge trial conducted by injection of A eromonas hydrophila for 17 days.Results indicated that iron significantly improved specific growth rate(SGR)(P＜0.01), feed intake(FI)(P＜0.01),protein efficiency ratio(PER)(P＜0.01),hepatopancreas weight (P＜0.01),hepatopancreas protein content(HPC)(P＜0.01),intestine weight(P＜0.01), intestine protein content(IPC)(P＜0.01),intestine length(P＜0.01),intestinal folds height (P＜0.01),activity of tryspin(P＜0.01),lipase(P＜0.01),amylase(P＜0.01),chymotrypsin (P＜0.01) in hapatopancreas and intestine brush border enzymes containing alkaline phosphatase(AKP)(P＜0.01),Na⁺,K⁺-ATPase(P＜0.01),gamma-glutamyl transpeptidase (γ-GT)(P＜0.01) and creatine kinase(CK)(P＜0.01).Quantities of Lactobacillus(P＜0.01), Bacillus subtilis(P＜0.01),Escherichia colii(P＜0.01) and Aeromonas hydrophila(P＜0.01) in intestine were also affected by dietary iron levels.Correlation analysis showed SGR and FER were all positive related to the development of hepatopancreas and intestine and digestive enzyme activities.There were great significantly correlation between FER and trypsin,lipase,amylase of intestine(r₁=+0.918,P＜0.01;r₂=+0.954,P＜0.01;r₃=+0.902, P＜0.01),and there were significant correlation between FER and AKP,Na⁺,K⁺-ATP,γ-GT in proximal intestine(PI),mid intestine(MI) and CK in whole intestine(r₁=+0.844,P＜0.05;r₂=+0.854,P＜0.05;r₃=+0.986,P＜0.01;r₄=+0.986,P＜0.01;r₅=+0.961,P＜0.01; r₆=+0.927,P＜0.01;r₇=+0.908,P＜0.01;r₈=+0.825,P＜0.05;r₉=+0.824,P＜0.05; r₁₀=+0.852,P＜0.05).Moreover,immune organ weight(P＜0.01),the counts of erythrocyte(P＜0.01) and leucocyte(P＜0.01),survival after vaccination(P＜0.01), phagocytic activity of leucocytes(P＜0.01),sim-immunoglobulin M(sim-IgM) levels (P＜0.01),anti-AH antibody titers(P＜0.01),serum lectin titers(P＜0.01),serum complement C3 and C4 levels(P＜0.01) and activity of serum acid phosphatase(ACP) (P＜0.01) and lysozyme(P＜0.01) were directly enhanced by graded iron levels.Serum iron was significantly enhanced with dietary iron levels(P＜0.01).This suggested that dietary iron promote growth of digestive and absorptive organ,enhance the ability of secrete digestive enzymes,improve activities of digestive enzymes and brush border enzymes,and enhance the ability of digestion and absorption of nutrient.Serum sim-IgM was directly correlated with C3,C4,serum lysozyme and serum ACP in intestine(₁=+0.961,P＜0.01; r₂=+0.940,P＜0.01;r₃=+0.961,P＜0.01;r₄=+0.909,P＜0.01).Besides,iron great significantly or significantly decreased malondialdehyde(MDA) and increased SOD,CAT, ASA,GST,GSH,GSH-Px,AHR,GR and protein carbonyl in serum(₁=-0.898,P＜0.01; r₂=-0.881,P＜0.01;r₃=-0.826,P＜0.05;r₄=-0.959,P＜0.01;r₅=-0.910,P＜0.01;r₆ =-0.939,P＜0.01;r₇=-0.906,P＜0.01;r₈=-0.826,P＜0.05;r₉=+0.956,P＜0.01).The effect of iron on the activites of antioxidative enzymes in hapatopancreas,intestine and muscle had similar pattern with serum.These results suggested that iron may enhance the activites of SOD,CAT,GSH-Px,GST and GR and increase GSH content,thus increased antioxidative defense systemes in fish.In considering these results,iron promoted development of digestive organs and the ability to secreting trypsin,lipase and amylase,and enhancing the absorbtion function of intestine to improve the ability to digesting and absorbing nutrients to so as to enhance the growth performance of aquatic animals.Meanwhile,iron promoted phagocytosis of leucocyte and bacteriolysis of serum lysozyme and ACP and increased Lactobacillus and Bacillus subtilis in intestine to depresse the reproduction of Escherichia colii and Aeromonas hydrophila in intestine in order to enhance non-specific immune ability of aquatic animals.Iron promoted the growth and development of immune organs and enhanced the responses of serum anti-AH so as to enhance specific immune ability and further improve disease of resistance.Iron can decrease lipid peroxidation and oxidative damage to proteins in Jian carp.By the broken-line analysis the optimum dietary iron requirement for serum iron,immune ability and antioxidative ability of juvenile Jian carp (11-64g) was determined to be 147.4mg/kg,124.6mg/kg and 123.2mg/kg,respectively.