Selection Of Lactobacillus Strains From Intestinal Mucous Of Broiler Chickens And Studies On Its Application

Lactobacillus strains were isolated from intestinal mucosa and screened out to develop a chicken-specific lactobacillus preparation,which would apply in chickens production.To further qualify the potential of lactobacillus for pathogen control and performance enhancement,the effect of a chicken-specific lactobacillus on improve growth performance,caecal microflora and immune function and protect in broilers was investigated.Twenty lactobacillus strains were isolated from fresh intestinal tissue samples taken from 21-day-old chickens.On the basis of stress-tolerance,6 strains were selected from 20 strains. Survival rates of 8 strains after being treated under pH 3.0 for 2h were more than 60%,6 strains could be survived under 0.1%-0.3%bile for 2h.3 strains(R5,R9,R19)out of these 6 strains showed antimicrobial inhibition toward the growth of both pathogenic Escherichia coli and Salmonella.According to their morphology,physiological and biochemical characteristics,two strains were identified as belonging to the genus of lactobacillus:R5 as Lactobacillus acidophilus, R19 as Lactobacillus crispatus,the another one were identified as Enterococcus faecalis.The biological characteristics of three lactobacillus strains were determined by investigation of grow curve and pH value of fermentation.Through these tests one strain(R5)were selected as potentially probiotic lactobacillus for its good characteristics,and the optimum fermentation time was about 18h.Survival rates of R5 strain after being treated under pH 3.0 and 0.3%bile for 2h were 68.15%and 42.06%,respectly.The diameter of inhibition zone of R5 strain toward pathogenic Escherichia coli and Salmonella was 21.17mm and 23.2mm,respectly.A total of 120 1-day-old Arbor Acres(AA)broiler chicks,obtained from a commercial hatchery,were randomized into 4 groups with 3 replications of 10:control group(basal diet), antibiotic group(basal diet+20mg/kg oxyteracyline),experimental lactobacillus group(basal diet +10~8 CFU/chick·day lactobacillus R5 culture in the drinking water),commercial lactobacillus group (basal diet +10~8 CFU/chick·day commercial lactobacillus culture in the drinking water).The experimental period was 21d.The effects of lactobacillus R5 on growth performance,caecal microflor and immune function were evaluated.The results showed that:throughout the experimental period,the ADG of experimental lactobacillus group(29.61g)was significantly higher than control group(27.6g)(p＜0.05);the feed to gain rations of commercial lactobacillus group(1.47)was significantly lower than control group(1.55)(p＜0.05),however there was no significant difference in feed to gain rations between commercial lactobacillus group and experimental lactobacillus group(1.47).Supplementation of experimental lactobacillus and commercial lactobacillus via the drinking water induced a clear reduction in mortality and diarrhea rate.The daily weight gain or feed to gain rations between the experimental lactobacillus and oxyteracyline-fed birds were not significantly different(p＞0.05).The experimental lactobacillus increased significantly the lactobacilli counts but decreased Escherichia coli counts in the caecal digesta(p＜0.05).The index of thymus of experimental lactobacillus group and commercial lactobacillus group were significantly(p＜0.05)higher than control group,the index of spleen of experimental lactobacillus group was significantly(p＜0.05)higher than control group.Both lactobacillus and oxyteracyline improved the level of IgG in serum(p＜0.05),only experimental lactobacillus improved the level of IgA in serum(p＜0.05).60 one-day-old AA broilers were randomized into 3 groups with 3 replications of 10:control group(basal diet),antibiotic group(basal diet+0.02%oxyteracyline),experimental lactobacillus group(basal diet+10~8CFU/chick·day experimental lactobacillus culture in the drinking water).The experimental period was 21d.All of 15-day-old chicks were challenged with 10~8 CFU/ml of pathogenic Escherichia coli.The results showed that:the mortality rates of control group,antibiotic group and experimental lactobacillus group were 20%,5%and 0%.Weight gain were improved by 3.96%(14d)and 9.13%(21d)in broilers administrated the experimental lactobacillus via the drinking water compared with the control birds.Feed to gain rations of antibiotic group and experimental lactobacillus group were lower by 8.95%and 7.89%than control group,respectively.