Effect Of Conjugated Linoleic Acid On Digestive And Immune Function Of Juvenile Jian Carp (Cyprinus Carpio Var. Jian)

The trial was conducted to study the effects of conjugated linoleic acid(CLA) on digestive function and immune function of juvenile Jian carp(cyprinus carpio Var. Jian). In trial, 1200 juvenile Jian carps with initial weight 10.71±0.02g were averagely allocated to 8 treatments with 3 replications, feeding diets with added CLA 0, 0.50, 0.80, 1.10, 1.40, 1.70, 2.00and 2.50 g/100g respectively for 60 days. After 60-day feeding, a challenge trial was couducted by injection of Aeromonas Hydrophila(AH) for 17 days to determine the effect of CLA on immune function of juvenile Jian Carp.The results showed as follows: CLA had not significant effect on weight gain, feed intake and feed conversion efficiency(P＞0.05), but with the increase of CLA, the weight gain had increased tendency; CLA had direct effect on hepatosomatic index (P＜0.05), but the hepatopancreas weight, intestine weight and intestine length were not affected by CLA(P＞0.05); The protein contents of hepatopancreas and intestine were significantly increased with the increase of CLA(P＜0.01); the activity of intestinal enzymes, including trypsin(P＜0.01), chymotrypsin(P＜0.05), lipase(P＜0.01), amylase(P＜0.01), alkaline phosphatase(P＜0.05), Na⁺,K⁺-ATPase(P＜0.01) andγ-gluta- myltransferase(P＜0.01) were significantly affected by CLA. The regression-analysis results indicated that there were quadratic regression relationship between the level of added CLA and the activity of intestinal enzymes, including trypsin(R²=0.8288, P＜0.05), chymotrypsin(R²=0.7989, P＜0.05), lipase(R²=0.8302, P＜0.05) andγ-glut- amyltransferase(R⁼0.9148, P<0.01). CLA had significant effects on the weights of head kidney(P＜0.01) and spleen(P＜0.05); the counts of red blood cells and leucocy- tes(P＜0.01); survival rate after vaccination against Aeromonas hydrophilaand(P＜0.01); lysozyme activity(P＜0.01); the level of lectine(P＜0.01); total iron-binding capacity (P＜0.01); the contents of complement C3(P＜0.01), complement C4(P＜0.01) and immunoglobulin M(P＜0.01). The regression-analysis results indicated that there were quadratic regression relationship between the level of added CLA and the head kidney weight(R²=0.9597, P＜0.01), spleen weight(R²=0.9389, P＜0.01); counts of red blood cells(R²=0.9770, P＜0.01), counts of leucocytes(R²=0.9853, P＜0.01); survival rate after vaccination against Aeromonas hydrophilaand(R²=0.8926, P＜0.05); lysozyme activit(R²=0.9856, P＜0.01); the level of lectine (R²=0.8413, P＜0.05); total iron-binding capacity(R²=0.9607, P＜0.01) and the contents of complement C3 (R²=0.8375, P＜0.05), complement C4(R²=0.7789, P＜0.01) and immunoglobulin M(R² =0.9647, P＜0.01). There were significant correlation between survival rate after vaccination against Aeromonas hydrophilaand and head kidney weight, red blood cell counts, leucocyte counts, lysozyme activity, the level of lectin, total iron-binding capacity, complement 3 contents, complement 4 contents, immunoglobulin M contents(r₁= +0.9730, P＜0.01; r₂=+0.9470, P＜0.01; r₃=+0.9150, P＜0.01; r₄=+0.9670, P＜0.01; r₅=+0.9670, P＜0.01; r₆=+0.9290, P＜0.01; r₇=+0.9410, P＜0.01; r₈=+0.8860, P＜0.01; r₉=+0.9330, P＜0.01). The path-analysis results indicated that serum complement 3 contents, serum total iron-binding capacity and serum lysozyme activity have significant direct effects on survival rate after vaccination against Aeromonas hydrophilaand(path coefficient: P_0.1=+1.1039, P_0.2=+1.3178, P_0.3=0.3209; decision coefficient: d_0.1=1.2187, d_0.2=1.7367, d_0.3=0.1030). Besides, serum immunoglobulin M content had some indirect effects on survival rate alter vaccination against Aeromonas hydrophilaand.In summary, the growh and development of digestive organs, the activity of digestive enzyme, the absorption ability of juvenile Jian Carp can be improved by the suplement of CLA. Meanwhile, CLA strengthened innate immunity by improving the ability of pathogen recognition, opsonization, lysis, inhibition; Acquired immunity can be strengthened by increasing the content ofimmunoglobulin M. Juvenile Jian carps appeared best ingestive function and survival rate as feeding the diets containing CLA 1.68～1.72g/100g, 1.87g/100g respectively.