Effect Of Supplementation Of Lysine And Methionine In Low Protein Dietary On Growth Performance And Ammonia Nitrogen Excretion Of Juvenile Grass Carp(Ctenopharyngodon Idellus)

In the present study,a 52-day growth trial was conducted in a semi flow-through system to explore the effect of supplementation of essential amino acids to low protein dietary on growth performance of juvenile grass carp with an initial body weight of 8.6 g.Five experimental diets were compounded:high protein diet(HP:31%protein),low protein diet(LP:29%protein),low protein diet supplementation with 0.2%lysine(LP ?LYS:29%protein + 0.2%lysine),low protein diet with 0.05%methionine supplementation(LP + MET:29%protein + 0.05%methionine),low protein diet with 0.2%lysine + 0.05%methionine supplementation(LP+LYS+MET:29%protein + 0.2%lysine+ 0.05%methionine).The growth performance,feeding rate,mortality,blood chemicals and the related gene expressions in hepatopancreas and muscle of juvenile grass carp were measured.The mechanism of lysine and methionine supplementation in low protein dietary on apparent digestibility and ammonia-N excretion were further discussed.The results are as follows:1.The effect of essential amino acid supplementation to low protein dietary on growth performance,of juvenile grass carpThe results showed that the specific growth rate,weight gain,protein efficiency ratio,protein retention efficiency were significant affected by dietary protein adding amino acid(P<0.05).The specific growth rate and weight gain in LP,LP+MET groups were significantly higher than those in the other groups.Protein efficiency ratio and protein retention efficiency in LP group were the highest.Survival rate in LP and LP+MET groups was significantly higher than those in the other groups,and the lowest was in HP group.Feed efficiency,feed rate,hepatosomatic index and viscerosomatic index were not affected by dietary protein and amino acid addition(P>0.05).In addition,moisture,ash,crude lipid and crude protein were also not affected by dietary protein and amino acid supplementation(P>0.05).Low protein diet supplementation with amino acid had significant effect on blood chemicals(P<0.05).Serum total protein and triglyceride at LP+LYS+MET group reached the top.Serum glucose in HP and LP+LYS groups was significantly higher than other groups.However,low protein diet supplementation with amino acid had no significant effect on urea nitrogen(P<0.05).Low protein diet with amino acid supplementation could stimulate the mRNA expression of TOR and 5S6K1 in hepatopancreas.Low protein diet could stimulate the mRNA expression of IGF-1 in hepatopancreas.2.The effect of supplementation amino acid in low protein dietary on the apparent digestibility of the diets' nutrients and ammonia-n excretion of juvenile grassThe apparent digestibility experiment was conducted in the feeding period.Feces were collected after 3h of feeding.Ammonia-N excretion was detected after feeding trial.The result indicated that low protein diet could significantly affect the apparent digestibility coefficient of dry matter(ADCd),apparent digestibility coefficient of protein(ADCp)and apparent digestibility coefficient of energy(ADCe)of the diet(P<0.05).ADCd was the highest in the LP+LYS+MET group,and was the lowest in the HP group.ADCp in HP group was significantly lower than those in the other groups(P<0.05),and there was no difference(P>0.05)among the four low protein diet groups.As for ADCe,the highest value was in LP+LYS group.Low protein diet with amino acid supplementation could significantly lower the ammonia-n excretion of juvenile grass carp(P<0.05).But among the four low protein diet groups,there was no significant differeence(P>0.05).The study indicated that high protein diet could not only reduce the apparent digestibility coefficients of the diet,but also increase the ammonia-N excretion rate of juvenile grass.