Effects Of Supplementation Of Crystalline Or Coated Threonine On Growth Performance, Functions Of Digestion, Absorption And Immune Of Juvenile Jian Carp (Cyprinus Carpio Var. Jian)

The effects of diet supplementation with crystalline threonine or coated threonine to juvenile Jian carp (Cyprinus carpio var. Jian) on growth performance, functions of digestion, absorption and immune was compared in a 60-day experiment. 300 juvenile Jian carps (initial weight 13.61±0.02 g) were randomly allocated to two groups; feeding diets supplemented with crystalline threonine or coated threonine respectively. Test diets were prepared by adding crystalline threonine or coated threonine to the basal diet to reach (caculated level) 3.91% of dietary protein. The analyzed values for threonine in the diets were both 4.07 and 4.07% of protein. The feeding trial was conducted in triplicate. 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 percent weight gain (PWG), specific growth rate (SGR), feed intake, productive protein value (PPV) and lipid production value (LPV) were improved with supplementation of coated threonine (P<0.01 or P<0.05). Hepatopancreas weight, intestine weight, intestine length (IL), hepatopancreas protein content (HPC), intestine protein content (IPC), and intestinal folds height were higher in group supplemented with coated threonine than those supplemented with crystalline threonine (P<0.01 or P<0.05). Meanwhile, the activities of tryspin and chymotrypsin in hapatopancreas and intestine, brush border enzymes containing alkaline Phosphatase (AKP), Na~+,K~+-ATPase, gamma-glutamyl transpeptidase (γ-GT) increased as diets supplemented with coated threonine(P<0.01 or P<0.05). Simultaneously, immune organ weight, blood hematocyte counts, activity of serum acid Phosphatase (ACP) and lysozyme, and serum complement C4 levels were enhanced by diets supplemented with coated threonine (P<0.01 orP<0.05). Plasma ammonia concentration was significantly lower in group added coatedthreonine than that supplemented with crystalline threonine (P<0.05). Leaching trialssuggested that almost all free threonine in crystalline threonine were lost after 15 min inthe buffered water, however, threonine lost from coated threonine platued after 120 min.In considering these results, diets supplemented with coated threonine couldimprove growth performance, the ability to digesting and absorbing nutrients and theimmune ability of juvenile Jian carp (13.61-53.43g). And the effect of coated threoninewas better than crystalline threonine, which was partly attributed to the reduction ofthreonine leaching by coating them with specific materials.