Effects Of Dietary Protein To Energy Ratios And Carbohydrate To Lipid Ratios On Growth Performance, Body Composition, Digestive And Metabolism Enzymes Activities Of Juvenile Jian Carp (Cyprinus Carpio Van.Jian)

The catabolism of protein, carbohydrates and lipids generate energy for the metabolic processes. Among the total, Protein is not only essential for tissue growth and maintenance, but also an expensive component of formulated diets. However, when either energy is not sufficient in a diet from non-protein sources or the ratio between carbohydrate and lipid is not optimal, protein may be catabolized to meet the energy requirements at the cost of nutrient supply somatic growth. If that, it could be not cost effective and result in excess ammonia in pond effluents. In our research, firstly a trial including the orthogonal design of dietary energy and protein levels was conducted to investigate the optimum protein and energy levels of juvenile Jian carp. Furthermore, another feeding trial of dietary carbohydrate-to-lipid ratios was conducted to investigate the optimum ratio between carbohydrate and lipid.1Effects of dietary protein and energy levels on growth performance, body composition and digestive enzymes activities of juvenile Jian carp (Cyprinus carpio var. Jian)The objective of this study was to evaluate the effects of dietary energy and protein levels on growth performance, body composition and digestive enzymes activities of juvenile Jian carp (average initial body weight,10±0.5g).960fish were randomly distributed into32tanks (3.0m×1.0m×0.8m) at a density of30fish per tank. Fish were fed eight practical diets with two digestible energy (DE) levels (13.5and14.5MJ/kg) and four crude protein (CP) levels (26%30%33%and36%) three times daily for8weeks. The results indicated that weight gain rate(WGR) and specific growth rate (SGR) increased with increasing dietary protein levels although no significant difference was observed (P>0.05). WGR, SGR and feed conversion ratio (FCR) improved significantly (P<0.05) as dietary energy levels increased. WGR and SGR of fish fed diets P36E14.5and P33E14.5 were significantly (P<0.05) higher than those of fish fed diets P26E13.5, P30L13.5and P33L13.5, but showed little difference with those of the other groups (P>0.05). Protein efficiency ratio and nitrogen retention efficiency (NRE) decreased significantly (P<0.01) as dietary protein levels increased. In addition, NRE increased significantly (P<0.05) as dietary energy levels increased. Contrary to moisture, relative feed intake, hepatosomatic index and whole-body lipid content decreased significantly (P<0.05) as dietary protein levels increased. Intestine protease activities increased significantly (P<0.05) as dietary protein levels increased, whereas little difference was observed in lipase and amylase activities (P>0.05). These results demonstrated that the diet contains33%protein and14.5MJ/kg energy is optimal for growth performance and feed utilization of juvenile Jian carp. Nitrogen-free extract could be used effectively by juvenile Jian carp and has a protein-sparing effect.2Effects of dietary carbohydrate-to-lipid ratios on growth performance, body composition, metabolism and digestive enzymes activities of juvenile Jian carp (Cyprinus carpio var. Jian)The objective of this study was to evaluate the effects of dietary carbohydrate-to-lipid ratios on growth performance, body composition, metabolism and digestive enzyme activities of juvenile Jian carp (average initial body weight,3.4±0.1g).720fish were randomly distributed into24tanks (3.0m×1.0m×0.8m) at a density of30fish per tank. Fish were fed six isonitrogenous (350g/kg) and isoenergetic (13.2MJ/Kg) diets with varying carbohydrate:lipid (CHO:L) ratios (2.3,3.0,4.0,5.6,7.7,12.1) three times daily for8weeks. The results indicated that best weight gain (WGR), specific growth rate (SGR), feed conversion Ratio (FCR), protein efficiency ratio (PER) and nitrogen retention efficiency (NRE)(P<0.05) were observed in fish fed diets with CHO:L ratio of7.7. The values of viscerosomatic index increased significantly (P<0.05) as dietary CHO:L ratios decreased. Whole body, carcass and liver lipid increased significantly (P<0.05) as CHO:L ratios decreased. There were no significant differences in whole body, carcass and liver crude protein among dietary treatments(P>0.05). Liver glycogen, blood glucose and insulin increased significantly (P<0.05) as CHO:L ratios increased. Activities of glucokinase and pyruvate kinase were stimulated significantly (P<0.05) by elevated levels of dietary carbohydrate. However, plasma total cholesterol and triacylglyceride levels increased linearly as dietary CHO:L ratios decreased(P<0.05). Intestine amylase activities increased significantly (P<0.05) as dietary CHO:L ratios increased, whereas Intestine lipase activities increased significantly (P<0.05) as dietary CHO: L ratios decreased. Based on a second-order polynomial regression analysis of WGR against dietary CHO:L ratios, corresponding to a CHO:L ratio of8.14, in a diet holding350g/kg of crude protein and13.2MJ/Kg of digestive energy, proved to be optimal for juvenile Jian carp. These results demonstrated that utilization of dietary lipid and carbohydrate was moderate in juvenile Jian carp, but the fish were a little more capable of utilizing carbohydrate compared with lipid.