| This experiment was conducted to compare the effects of dietary supplementation with uncoated tryptophan(UCT) or coated tryptophan(CT) on growth performance,functions of digestion,absorption and immune of juvenile Jian carp(cyprinus carpio var.Jian).A total of 300 fish(initial weight 7.73±0.03 g) were randomly distributed into each of six glass tanks with three replicates per treatment,feeding a diet containing UCT and a diet containing CT for 8 weeks respectively.After the growth trial,30 fish in each treatment were randomly assigned to a challenge trial conducted by injection of aeromonas hydrophila(AH) for 17 days.Results showed that:compared with group whose diet containing UCT,fish fed CT supplement diet had higher percent weight gain(PWG),specific growth rate(SGR), protein efficiency ratio(PER),productive protein value(PPV),lipid production value (LPV),hepatopancreas weight,hepatosomatic index,intestine length,intestine weight, intestosomatic index,intestinal folds height,activity of tryspin and lipase in hapatopancreas and intestine,chymotrypsin in intestine,alkaline phosphatase(AKP),Na~+, K~+-ATPase and gamma-glutamyl transpeptidase(γ-GT) in intestine,head kidney weight, spleen weight,head kidney index,spleen index,leucocyte counts,survival after vaccination,activity of serum lysozyme,total iron-binding capacity and lower feed conversion ratio(FCR)(P＜0.05 or P＜0.01).Besides,plasma ammonia concentration was significantly lower in group CT than group UCT(P＜0.01).Leaching trials suggested that all uncoated tryptophan were dissolved in the borate buffer after 15 min,however,almost all coated tryptophan were dissolved in the borate buffer after immersion for 120 min.In conclusion,our study showed that diets supplemented with CT could better improve growth performance,the ability to digesting and absorbing nutrients and the immune ability of juvenile Jian carp than UCL.
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