Effects Of Dietary Phosphorus On Growth Performance, Functions Of Digestion, Absorption, Immune And Antioxidative Of Juvenile Jian Carp (Cyprinus Carpio Var. Jian)

This experiment was conducted to study the effects of dietary phosphorus levels on growth performance, digestive and absorptive function, immune and antioxidant abilities of juvenile Jian carp (Cyprinus carpio var. Jian) (initial weight 7.17±0.01 g). Practical diets with six levels of supplemental monosodium phosphate (0.17%,0.36%,0.55%,0.73%, 0.92% and 1.10%) were respectively fed to quadruple groups of 50 fish for 9 weeks. After the growth trial,30 fish with similar weight in each treatment were assigned to a 17-day challenge trial conducted by injection Aeromonas hydrophila.Results indicated that phosphorus improved specific growth rate (SGR), feed intake (FI), protein efficiency ratio (PER), protein deposition value (PPV), lipid deposition value (LDV), ash depostition value (ADV), hepatopancreas weight (HW), hepatopancreas protein content (HPC), intestine weight (IW), intestine length (IL), tryspin, amylase,. chymotrypsin activities in hapatopancreas and intestine brush border enzymes activities including alkaline phosphatase (AKP), Na+,K+-ATPase, gamma-glutamyl transpeptidase (y-GT) and creatine kinase (CK) (P<0.01 or P<0.05). Simultaneously, vaccinated survival rate, immune organs weight, blood hematocyte counts, phagocytosis of leucocyte, total iron-binding capacity and activities of serum acid phosphatase (ACP) and lysozyme were enhanced by graded phosphorus levels (P<0.01 or P<0.05). Moreover, quantities of Bacillus acidi-lactici, Bacillus coli and Aeromonas in intestine were affected by dietary phosphorus levels (P<0.01 or P<0.05). Dietary phosphorus levels also increased MDA, protein carbonyl and GSH content, activities of GR, CAT, GST, SOD, GSH-Px and the ability of ASA, AHR in serum, hepatopancreas, intestine and muscle. Correlation analysis showed that SGR was positively related to HW, HPC, IW, intestinal trypsin and amylase activities, and was negatively related to intestinal lipase activity (P<0.01). FE was positively related to HW, HPC, IW, hepatopancreas amylase activity, intestinal trypsin, amylase and absorptive enzymes activities (P<0.01 or P<0.05), but FE was negatively related to intestinal lipase activity (P<0.05). The serum MDA content was positively related to serum GST activity and GSH content (P<0.01 or P<0.05), and negatively related to serum GR, CAT, SOD activities and AHR ability (P<0.01 or P<0.05).Considering these results, phosphorus improved the growth and feed efficiency of Jian carp. Phosphorus improved digestive and absorptive ability by promoting the growth and development of digestive organs, the activities of tryspin, amylase, alkaline phosphatase, Na+,K+-ATPase, gamma-glutamyl transpeptidase and creatine kinase. At the same time, phosphorus promoted non-specific immune ability of Jian carp by increasing phagocytosis of leucocyte, serum lysozyme and ACP activities, serum iron-binding capacity. Dietary phosphorus promoted fish antioxidant capacity by removing superoxide anion and lipid peroxidative product. By the broken-line analysis, the optimal dietary available phosphorus requirement for SGR of juvenile Jian carp (7.17-63.8 g) was estimated to be 0.52%.