Effects Of Source Peptide Replacing Fish Meal On Water Quality And Growth Of Juvenile Grass Carp (Ctenopharyngodon Idellus) And Yellow Catfish (Pelteobagrus Fulvidraco)

3 feeding trials were conducted to investigate the effect of Source peptide(SP) replacing fishmeal on water quality,growth and feed utilization of juvenile grass carp (Ctenopharyngodon idellus) and yellow catfish(Pelteobagrus fulvidraco).In the first feeding trials,five experimental diets were formulated isonitrogenously and isoenergeticly with SP replacing fishmeal at level of 0%,25%,50%,75%and 100%, and fed to grass carp(initial body weight 50 g) at a daily ratio of 3%～5%of total tank biomass at 09:00 and 16:00 every day to evaluate the effects of SP replacing fishmeal on growth,feed utilization and body composition of grass carp.The results showed that the weight gain rate,specific growth ratio,feed efficiency and protein efficiency ratio were highest in group 0%,and decreased as the increasing replacement level of SP.These indices of group 100%were significantly lower than group 0%,but the differences were not significant among other groups;the viscera-somatic index and hepato-somatic index were not differed from each group while the mesenteric lipid index increased as the replacing level increase and was significantly higher in group 100%than in group 0%. Profit analysis shows that diet 50%has the highest profit gain.In the second trail,five diets were formulated isonitrogenously and isoenergeticly with SP replacing fishmeal at level of 0%,25%,50%,75%and 100%and fed to yellow catfish(initial body weight 3～4 g) to evaluate the effects of SP replacing fishmeal on growth,feed utilization,body composition as well as fat retention ratio and protein retention ratio of juvenile yellow catfish.The results indicate that the weight gain rate, specific growth ratio,feed efficiency and protein efficiency,protein retention efficiency of group 25%were significantly higher than other groups,with a sequence of 25%＞50%＞0%＞75%＞100%;the fat retention efficiency was significantly higher in group 25%than group 75%and 100%,with a sequence of 25%＞50%＞0%＞75%＞100%;the viscera-somatic index and hepato-somatic index were not different significantly among all groups while the mesenteric lipid index of group 75%was significantly lower than groups 0%,25%;the crude protein content,ash content were not effected by the replacement. This suggest that proper replacing levels(25%,50%) can imorove the growth of juvenile yellow catfish and feed utilization,and thus reduce the feed cost.The third trail was conducted to feed the grass carp by feeds of the first trail to investigate the effects of SP replacing fishmeal on water quality.The results showed that total phosphorus concentration(TP) value was droped first then rose up as the replacing level increases, with the lowest in group 50%;the ammonia nitrogen concentraion(NH₃-N) and nitrate nitrogen concentration(NO₃-N) of the substitution groups were higher than group 0%and the value of group 100%was significantly higher than group 0%at the end of the trail.