Effect Of Yeast Culture On Growth Performance,Immune Function And Intestinal Flora Of Broiler

This study aimed to investigate the effect of dietary supplementation of yeast culture(YC) that was developed at the lab on growth performance, apparent nutrient digestibility, blood index, immune function and caecum microflora in broilers and to determine the optimal dose of YC in broilers.Chapter one: The effect of dietary supplementation of yeast culture(YC) on growth performance, apparent nutrient digestibility, blood index, and immune function in broilers and to determine the optimal dose of YC in broilers. Using single factor randomized trial design completely. A total of 360 Arbor Acres broilers were fed for 7 days, weighed and distributed into 6 treatment groups depending on the concentration of YC in the diet(control, 0.2%, 0.4%, 0.6%, 0.8% and 1%). Each treatment had 6 replicates with 10 chicks per replicate. The chicks were fed the diet for 42 days. Dietary supplementation of YC did not have any effect on feed intake(P>0.05). Treatment with 0.8%YC significantly increased the average daily gain and feed conversion ratio, digestibility of fat, calcium, and phosphorus, total protein content, and serum glucose concentration. Immunoglobulin G content of the 0.4%, 0.6%, 0.8%, and 1.0%YC groups was significantly higher than that of the control group(P<0.05). Dietary supplementation with 0.8%YC significantly increased the antibody titers(P<0.05), but the serum immunoglobulin A level was not influenced by the YC in the diet. The Bursa of Fabricius and thymus indices were influenced by dietary supplementation with 0.8%YC on days 21 and 42, respectively(P < 0.05).Chapter two: The effect of YC cecum bacterial community. The result showed that the concentration of acetic acid and total volatile fatty acids were significantly higher than that of the control group when supplied with 0.8%YC on day 21(P<0.05). Dietary supplementation of YC did not have any effect on volatile fatty acids on day 42(P>0.05). Microbial diversity of cecum bacterial community was increased by YC dietary supplementation. And four types of bacteria in the cecum were found by polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE): They are firmicute, bacteroidetes, actinobacteria and proteobacteria. Alistipes sp., Rikenella sp., Firmicute and Stomatobaculum longum were the specific bacteriums when dietary supplementation with 0.8%YC.Chapter three: The effect of YC on caecum microflora of broilers by Real-time PCR. The result showed that: on d 21, 0.6%, 0.8% and 1.0%YC groups increased the ruminococcus and propionibacterium(P<0.05); The bacteroides of YC groups were significantly higher than that of the control group(P<0.05); The bifidobacterium was significantly higher when supplemented with 0.4%, 0.6%, 0.8%, and 1.0% YC(P<0.05); Clostridiales of 0.8% and 1.0% YC groups were higher than that of the control(P<0.05); Dietary supplementation with YC had no effect on sphingomonas and enterobacteriaceae(P>0.05). On d 42, 1.0%YC groups increased the ruminococcus(P<0.05); Dietary supplementation with 0.4%, 0.6% and 0.8%YC increased the bacteroides and bifidobacterium but decreased the enterobacteriaceae(P<0.05); 0.8%YC group increased the sphingomonas(P<0.05); And there was no effect on clostridiales and propionibacterium when supplied with YC in the diet(P>0.05).