COMPARATIVE STUDIE ON NITROGEN BUDGET AND ENERGY BUDGET OF JIAN CARP (CYPRINUS CARPIO VAR.JIAN)AND GIBEL CARP (CARASSIUS AURATUS GIBELIO)FED DIETS WITH DIFFERENT QUALITIES

A 552 day growth trial was conducted to investigate nitrogen budget and energy budget of Jian carp ( Cyprinus carpio var.jian)and Gibel carp( Carassius auratus gibelio) fed diets with different quality.Low quality diet (LQ diet)and high quality diet (HQ diet)were tested.LQ diet contained 33.91% dietary protein which is mainly from soybean meal while HQ diet contained 45.59% dietary protein which is mainly from fish meal. The initial average body weight of fishes was from 5.58g to 5.82g.The trial was carried out in a system consisting of 12 self circulation fiberglass tanks(volume:320L) with conical bottoms.During the experiment, dechlorined tapwater was added into each tank at the rate of about 500mL/min.Dissolved oxygen was maintained above 6mg/L,ammonia below 0.15mg/L and the temperature 28±1℃ . The photoperiod was 12hL:12hD with the light period from 8:00 to 20:00. The results showed that,when fed LQ diet,nitrogen intake was not significantly affected by fish strains while recovery nitrogen for growth in Jian carp was lower than that in Gibel carp.When fed HQ diet, nitrogen intake in Jian carp was lower than that in Gibel carp,while recovery nitrogen for growth was not significantly affected by fish strain. For Jian carp,nitrogen intake was not affected by diet quality, while recovery nitrogen for growth of fish fed HQ diet was higher than that fed LQ diet.For Gibel carp,nitrogen intake was higher in the fish fed HQ diet than that fed LQ diet while recovery nitrogen for growth was not affected by diet quality. There was no significant difference in food energy intake and assimilation energy in two fishes while growth energy in Jian carp was lower than that in Gibel carp when fed LQ diet.There was no significant difference in food energy, assimilation energy, growth energy and metabolism energy between two fishes when fed HQ diet.For Jian carp,food energy,assimilation energy,metabolism energy and faecal energy were lower while growth energy was higher when fed HQ diet than that when fed LQ diet.For Gibel carp,food energy,growth energy and faecal energy were lower when fed HQ diet than that when fed LQ diet while assimilation energy and metabolism energy were not affected by diet quality. Nitrogen budget and energy budget were significantly affected by both diet and fish strain. When fed LQ diet,the proportion of food nitrogen and energy deposited in growth in Jian carp was lower than those in Gibel carp while the proportion of excretion nitrogen,excretion energy and metabolism energy in Jian carp was higher than those in Gibel carp.There was significant difference in nitrogen and energy budget in two fishes when fed HQ diet.In Jian carp,nitrogen and energy budget was significantly affected by diet quality.The proportion of growth nitrogen and growth energy was significantly lower when fed LQ diet than that fed HQ diet while the proportion of excretion nitrogen, faecal energy and metabolism energy when fed LQ diet was significantly higher than that fed HQ diet. Nitrogen and energy budget in Gibel carp was not affected by diet quality. In conclusion, when fed LQ diet,the utilization of nitrogen and energy in Jian carp is poorer than that in Gibel carp. Compared to Gibel carp,the utilization of nitrogen and energy in Jian carp is more affected by diet quality.