Effect Of Yeast Culture On Modulating Digestion And Immunity In Broilers

Three experiments were conducted to study the different supplement level of Yeast Culture (YC) onperformance, development of intestinal tract, availability of nutrients, immune function and modulatingmechanism of alleviating immunological stress.This study aimed to serve as the base for further researchand application on Yeast Culture (YC).The first part of the experiment: 225 broilers randomly assigned to three groups, with three replicatesper group, and 25 broilers per replicate. The control group was provided with the basal diet (not includingany drug additive), YC was added to the basal diet at the level of 0.15％, 0.3％respectively. The feed trialstarted at 1d and ended at 42d. Weight, feed intake and feed efficiency were measured everyweek. Metabolic trial was done at 40 d of age. At day 28 and day 42, six broilers per group were killed andgot the duodenum, jejunum, ileum and cecum to test structure. The results showed that: The dietary0.3％YC decreased significantly (P＜0.05) the Daily Feed Intake (DFI) of broilers, and the 0.15％YC didnot decreased significantly (P＞0.05) the DFI of broilers. Compared with control, the dietary 0.3％YCincreased highly significant (P＜0.01) the Daily Weight Gain (DWG) and Feed Conversion Ratio (FCR) ofbroilers (P＜0.01). Compared with control, the dietary 0.15％YC increased significant (P＜0.05) the DWGand FCR of broilers (P＜0.05). The dietary 0.15％YC and 0.3％YC improved significantly the performanceof broilers, especially the dietary 0.3％YC. compared with control, the dietary 0.15％YC and the dietary0.3％YC increased the retained N and remained N/N intake lightly (P＞0.05). The dietary YC did notimprove significantly availability of dietary crude fat (P＞0.05). The dietary 0.3％YC improved highlysignificant availability of dietary crude fiber, compared control and the dietary 0.15％YC, it increasedhighly significant by 50.71％(P＜0.01) and 33.97％P＜0.01) respectively. Compared with control, thedietary 0.3％YC increased highly significant apparent metabolizable energy (AME)by4.78％(P＜0.01).The second part of the experiment: 300 broilers randomly assigned to four groups, with threereplicates per group, and 25 broilers per replicate. Not immune group was provided basal diet (notincluding any drug additive), and didn't inoculated any vaccine; the dietary 0.15％YC group was providedbasal diet with 0.15％YC, and inoculated La Sota for double amount; the dietary 0.3％YC group wasprovided basal diet with 0.3％YC, and inoculated La Sota for double amount. The experiment wasconducted to study the effect of the different supplement level of YC on development of immune organ,humoral immunity function and cellular immune function. At day 7, 14, 21, 28, 35, 42, six broilers pergroup were killed and removed the immune organs (Spleen, Left Thymus, Bursa.F.) to test weights; At day1, 8, 15, 22, 29 after immune, six broilers per group were killed and collected blood from wing's vein,and then separated serum to test New castle disease antibody titer and IgG; At day 28 and 42, collectedblood from wing's vein, and then separated serum to test total serum protein and albumen. At the sametime, blood from wing's vein was collected to test the lymphocyte proliferation and ANAE+. The resultsshowed that: the dietary 0.3％YC improved significantly the development of immune organ (Spleen, LeftThymus, Bursa.E) (P＜0.05), and improve significantly the immune effect after inoculating. Comparedwith control, the dietary 0.3％YC increased significantly peak value of New castle disease antibody titerby 12.77 (P＜0.05); the dietary 0.3％YC increased highly significant peak value of IgG by 13.75％(P＜0.01).At the end of the experiment, compared with control, the dietary 0.3%YC increased highly significant peak value of New castle disease antibody titer by 50％(P＜0.01); the dietary 0.3％YC increased highlysignificant peak value of IgG by 20％(P＜0.01). The dietary 0.3％YC improve the concentration of globulinlightly (P＞0.05). In addition, the dietary 0.3％YC improved the lymphocyte proliferation and ANAE+ in away.The third part of the experiment: 90 one day AA broilers randomly assigned three groups, 30broilers per group, the diets were the same as experiment 1. At 30 days of age, these broilers were assignedagain. 12 male broilers were chosen from each group and randomly assigned them to 2 groups, 3 replicatesper group, 2 broilers per replicate. The experimental design is 2×3 factors (2 Immunological tress×3diets). The diet treatments were the same as experiment 1. Immunological tress treatments containinjecting saline or Newcastle disease intermediate vaccine (NDⅠ). At 30 day, half of the broilers fromeach treatment were injected large dose NDⅠ(25×), others injected saline. Immunological tress model wasproduced by injecting large dose NDⅠ, and the experiment was conducted to study alleviating action ofYC on immunological stress induced by NDⅠinjection in broilers. The whole experimental stage containtwo stage, the first stage was from ld to 5d after injecting NDⅠ, the second stage was from 6d to 11d afterinjecting NDⅠ. The initial body weight, the body weight of the 5th day after injecting NDⅠand the finalbody weight were measured, as well as feed intake and feed efficiency at the 5th day after injecting NDⅠand the end of the experiment. At day 1, 3, 5, 7, 9, 11 after injecting ND I, collected blood from wing'svein, and then separated serum to test blood glucose and IgG. The results showed that dietary YC couldsignificantly inhibit declining of feed intake, body weight gain, IgG and rising of blood glucose in broilersiniected NDⅠ, and showing significant alleviating action on immunological stress.