Selection And Application On Formula Of Low Nitrogen Discharge Feed For Grass Carp(Ctenopharyngodon Idellus)

Sixteen diets were formulated to study the influences of dietary protein and energy on grass carp,selected a group of feed formula with better growth performance,lower total nitrogen excretion rate.Then an experiment was conducted for a period of 283 days without water exchange(close system) to determine the effects of feeding on the variation rules of water quality and the budget of nitrogen and phosphorus in ponds with grass carp as the dominant cultured species.Evaluate the result of feed to reduce nitrogen and phosphorus emissions,so as to provide the basis for low nitrogen discharge feed.1.Selection on formula of low nitrogen discharge feed under laboratory conditionsIn each group using fish meal and soybean meal as protein source,mixture of equally proportioned fish oil and soybean oil as lipid source.Sixteen diets were formulated,containing four protein levels(20%,25%,42%,46%),each with four lipid levels(4.5%,8%,11.5%,15%).Each diet was fed to triplicate groups of grass carp with initial average weight(16.84±0.28)g.During the experiment period of ten weeks,the temperature ranged from 23℃to 29℃,dissolved oxygen content above 5 mg/L.At the termination of experiment,the fish were starved for 24 h before harvest.The results showed that:under the content of protein level was lower in the diet, with the improving of dietary lipids levels,specific growth rate,protein efficiency ratio and protein retention value increased significantly(P＜0.05),feeding rate and feed conversion rate decreased significantly(P＜0.05).But had no significiant difference while the content of protein level was higher(P＞0.05).No significant difference in condition factor was found among all groups(P＞0.05).Total nitrogenous excretion rate of fed with lower protein was lower than the fed with higher protein.Under the same protein level in the diet,total nitrogenous excretion rate decreased with the increased of dietary lipid levels.The amylase activity decreased and lipase activity increased with the increased of dietary lipid levels,but protease activity had no significant difference among all groups(P＞0.05).Under the same protein level in the diet,the content of lipid and protein in the whole fish increased with the improving of dietary lipid levels,while the protein was 35%,the content of protein had no significant difference(P＞0.05).While the content of protein level was lower,the protein-sparing effect of lipid had significant,when the content of protein level was higher,the protein-sparing effect of lipid had no significant.The Fish fed the diet with protein and lipid levels of 25%and 15%,protein/energy ratio of 15.20mg/kJ had the better growth performance and total nitrogenous excretion rate.2.Application on formula of low nitrogen discharge feed in ponds with grass carp as the dominant cultured speciesAn experiment was conducted for a period of 283 days without water exchange (close system) to determine the effects of feeding on the variation rules of water quality and the budget of nitrogen and phosphorus in ponds with grass carp as the dominant cultured species.During the breeding,water quality was measured for 10 times.The results showed that,the concentrations of ammonia nitrogen,nitrite nitrogen, nitrate nitrogen,total nitrogen and total phosphorus in the group of treatment diet on June 12-November 1,July.5 and August 29,July 5-November 1,August 1-November 1, August 1-December 23 had significantly lower than the control group,but the concentrations of suspended solids had no significant difference(P＞0.05).Feed conversion rate of feed-feeding fishes and the total feed conversion rate in the group of treatment diet lower than the control group,the utilization rate of N and P higher than the control group.