Effect Of Dietary Riboflavin On Growth And Function Of Digestion And Absorption Of Juvenile Jian Carp (Cyprinus Carpio Var. Jian)

This experiment was conducted to study the effect of dietary riboflavin on growth, digestive and absorptive function and to evaluate the dietary riboflavin requirement of Jian carp (Cyprinus carpio var. Jian). A total of 1050 juvenile Jian carp (initial body weight 23.39±0.06 g) were randomly divided into seven groups of each three replicates. Seven diets (320g protein and 45.6 g lipid kg^-1) were formulated to contain 1.25, 2.71, 4.22, 5.78, 7.23, 8.83 and 11.44mg riboflavin kg^-1 diet. Each diet was randomly assigned to three aquariums of fish for 6 weeks.The results showed as follows: anorexia was observed after three weeks. Riboflavin deficiency symptoms such as fin corroded, scales stopped and epidermis damaged and bleeded were observed at the end of experiment. Weight gain, feed intake, feed conversion efficiency, hepatopancreas weight, intestine weight, intestine length, height of proximal and distal intestinal folds , tryspin, chymotrypsin, lipase, alkaline phosphatase, Na⁺,K⁺-ATPase,γ-glutamyl transpeptidase, MDA of serum were significantly affected by the increasing dietary riboflavin levels. There was a significant correlation between weight gain and feed intake and feed efficiency (r₁=+0.978, r₂=0.997). There was a significant direct effect of feed intake and feed efficiency on weight gain. The direct path coefficient was +0.255,+0.761, respectively. It indicated that feed intake and feed efficiency were contributed to weight gain. There was a significant correlation between protein, lipid and ash protein and feed efficiency (r₁=+0.985, r₂=+0.859, r₃=+0.950). There was a significant direct effect of protein deposition on feed efficiency. There was also a significant correlationship between chymotrypsin, Na⁺,K⁺-ATPase,γ-glutamyl transpeptidase and creatine kinase in intestine (r₁=+0.841, r₂=+0.980, r₃=+0.950, r₄=+0.880). The direct path coeffitient between chymotrypsin and Na⁺,K⁺-ATPase in intestine and protein depositon was +3.010 and +3.039, respectively. It means chymotrypsin and Na⁺,K⁺-ATPase in intestine play an important role in protein depositon. There was a significant correlation between feed efficiency and heptopancrease weight index, protein content of heptopancrease and intestine, intestine weight, length. There was also a significant correlation between feed efficiency and activity of trypsin, chymotrypsin, lipase, amylase, alkaline phosphatase, Na⁺,K⁺-ATPase,γ-glutamyl transpeptidase and creatine kinase. It indicated that intestinal enzyme play an important role in feed efficiency. The regression formula between dietary riboflavin and protein retention ration, activity of trypsin, lipase, amylase, alkaline phosphatase, Na⁺,K⁺-ATPase,γ-glutamyl transpeptidase and creatine kinase in intestine was Y₁=6.494X₁+7.987(P<0.01, R²=0.926), Y_max=42.15; Y₂=0.178X₂+1.953 (P<0.01, R²=0.934), Y_max=2.95; Y₃=74.203X₃+7.369 (P<0.01, R²=0.986), Y_max=474.38; Y₄=1.175X₄+19.715, (P<0.01, R²=0.995), Y_max=26.84; Y₅=1.19X₅+190.82(P<0.01, R²=0.984), Y_max=602.13; Y₆=3.725X₆-3.550 (P<0.05, R²=0.919), Y_max=20.53; Y₇=1.053X₇+22.286 (P<0.05, R²=0.93, P<0.05), Y_max=27.65, respectively. The dietary riboflavin requirement of juvenile Jian carp was 5.3 mg/kg,5.6mg/kg,6.3 mg/kg,6.1 mg/kg,5.7 mg/kg,6.7 mg/kg,5.1 mg/kg, respectively. The results indicated that the dietary riboflavin requirement of juvenile based on protein retention ration or feed efficiency is similar to that based on weight gain. Except forγ-GT, the dietary riboflavin requirement of juvenile based on activity of trypsin, lipase, amylase, alkaline phosphatase, Na⁺,K⁺-ATPase or creatine kinase in the intestine was a little higher than that based on weight gain.In summary, dietary riboflavin resulted in growth improvement of juvenile Jian carps through increasing feed intake and utilization. The increasing of digestive ability was due to intestinal growth, enhancement of enzyme activity accompanied by increasing dietary riboflavin. When broken-line analysis was used, dietary riboflavin requirement of juvenile Jian carp was 5.0 mg/kg based on weight gain. And according to trypsin activity and Na⁺,K⁺-ATPase activity, dietary riboflavin requirement of juvenile Jian carp was 5.6m and 5.7mg/kg respectively.