EFFECT OF D IETARY REPLACEM ENT OF FISHM EAL PROTEIN BY SOYBEAN M EAL PROTEIN ON GROW TH PERFORMANCE, M ETABOL ISM AND IMM UNITY OF GIBEL CARP (CARASSIUS AURATUS GIBEL IO)

A 162weeks growth was conducted to evaluate the effect of replacement of dietary fishmeal by soybean meal on growth performance, feed utilization, nitrogen metabolism and immunity in gibel carp. Four isonitrogenous and isocaloric dietswere formulated. Each dietwas fed to triplicate groups of fish with the initial weight at about 2.32 g. Soybean meal was used to replace 0 (Control, D1), 20% (D2), 80% (D3) and 100% (D4) of dietary fishmeal protein1 The fish was reared in a semi-recirculating system. During the experiment, water temperature was 23-30℃, photoperiod was 12D∶12L with the light period from 08: 00 to 20: 00, dissolved oxygen was above 5 mg/L, ammonia2N (NH4+-N plus NH3-N) was less than 0.5 mg/L, pH was about 6.4. Fish were fed to satiation twice daily (9: 00 and 15: 00). At the beginning of the experiment, healthy fish (initial body weight about 2.32 g) were batch weighed after 24h feed deprivation and randomly distributed into the 12 tanks (40 fish per tank). The tankswere randomly assigned the four diets. Fifty fish were taken from the remaining fish and frozen for initial fish body chemical analysis. During the experiment, an excess amount of feed was fed to fish and uneaten feed were collected after 1h in each feeding, dried at 60℃ and reweighed. Leaching rate of uneaten feed in tankswas estimated by placingweighed feeds into a tank without fish for 1h and then recovering, drying and reweighing. The average leaching rate was used to calibrate the amount of uneaten feed1 Faeceswere collected after uneaten feed collection at the startof the experiment and through all the experimentperiod after7d. To minimize nutrient leaching in faeces, only fresh and intact faeces were collected1 Faeces were dried at 70℃ for digestibility determination.At the end of the trial, the fish were starved for 1d and batch weighed1 Fish were killed by a blow on the head and blood sampleswere collected (24h after last feeding) from the caudal vein of six fish from each tank at the end of the feeding trial by using heparinized syringes. Blood was centrifuged at 3500 r/min for 15 min, plasma-separated and stored at -80 ℃. The remaining fish in each tank were taken for final fish body composition analysis1 The results showed that feeding rate (FR), specific growth rate (SGR), feed conversion efficiency (FCE), protein retention efficiency (PRE) and energy retention efficiency (ERE) decreased significantly (p p p p p p <0.05). In conclusion, the results from this study showed adverse effects of inclusion of the soybean meal in dietson growth performance, feed utilization, nitrogen metabolism and immunity in gibel carp. The palatability was not negatively affected when soybean mealwas included in the diets1 Unbalanced amino acid composition of soybean meal diets seem to be the main reason to influence growth performance and nitrogen load of gibel carp.