Effects Of Different Lactobacillus Strains And Dosages On Growth Performance, Cecal Microflora And Immunity Of Broilers

The experiment was conducted to study the effects of homology lactobacillus preparation with different strains and dosages in diet on growth performance, cecal microflora and immunity of broilers. The objective of this study was to compare application of different strains and find the more suitable dosages in broilers, reveal the relations between homology lactobacillus, intestinal flora and immunity of broilers, which would provide theoretical basis for the application of probiotics in broilers.Monofactorial experiment design was adopted. 288 one-day-old broilers were randomly assigned to 6 groups with 4 replications of 12 broilers each. The live lactic acid bacteria population of lactobacillus preparation were 5~6×10~8cfu/g. The experimental treatments were divided as follows: GroupⅠ, the control, basal diets; GroupⅡ, the antibiotic, basal diets + 0.01% flavomycin; GroupⅢ, basal diets + 0.2% L.graminis preparation; GroupⅣ, basal diets + 1.0% L.graminis preparation; GroupⅤ, basal diets + 0.2% L.gasseri preparation; GroupⅥ, basal diets + 1.0% L.gasseri preparation. The live lactic acid bacteria population of lactobacillus preparation were equivalent between groupⅢandⅤ, groupⅣandⅥ. The trial lasted 28 days. The effects of homology lactobacillus preparation with different strain and dosages in diet on growth performance, cecal microflora and immunity of broilers were studied in the trial.The results are as followed:(1) Supplementation of lactobacillus in the diets could increase average daily gain in varied degrees and feed conversion ratio were decreased significantly compared with the control group (p<0.05). The improved effect of 1.0% lactobacillus with same strain on growth performance was better than 0.2%, and L.graminis surpassed L.gasseri, there was not significant difference between lactobacillus group and antibiotic group (p>0.05).(2) Compared with the control, supplementation of lactobacillus significantly increased lactobacillus quantity and effectively inhibitted E.coli in cecum (p<0.05), antibiotic inhibited both lactobacillus and E.coli.(3) Supplementation of lactobacillus in the diets could promote variably the growth and development of immune organs, spleen index was raised significantly compared with the control group (p<0.05), thymus gland index and bursa of fabricius index were higher than the control group, but there is not significant difference between them (p>0.05). (4) The content of IgG of the experimental broilers in group with high dose of lactobacillus were significantly higher than the control group (p<0.05), and serum IgA of the experimental broilers in group with high dose of lactobacillus were significantly higher than the control group in 2 week (p<0.05), and high dose treatment significantly surpassed low dose of the same strain on IgG and IgA in 2 week (p<0.05). In time of 2 week, the content of SIgA of broilers with high dose of L.graminis were significantly higher than the control group (p<0.05); contrasted with the control group, the content of SIgA of broilers with L.graminis or 1.0% L.gasseri were significantly higher in 4 week (p<0.05).(5) The content of serum IL-2 of the experimental broilers fed with lactobacillus were higher than the control group, IL-2 level of high dose group were significantly higher than the control group (p<0.05). T lymphocytes proliferative response in peripheral blood of the experimental broilers fed with lactobacillus were better than the control group, T lymphocytes conversion of high dose group were significantly higher than the control group (p<0.05). The results showed Newcastle disease hemagglutination inhibition antibody titers of the experimental broilers fed with lactobacillus were higher than the control group, high dose L.graminis group were significantly higher than the control group in time of 2 week (p<0.05).(6) The length of small intestinal villi and intestinal wall depth of the experimental broilers fed with lactobacillus were higher than the control group, cryptae depth were lower than the control group, there were significant difference between the high dose lactobacillus and the control group (p<0.05).In a word, our study indicated that homology lactobacillus could effectively promote the growth performance of young broilers, the population of cecal benifical bacteria and the immunity. And high dose of lactobacillus was better than low dose. Well, in the same dose of lactobacillus, L.graminis was better than L.gasseri.