Effects Of Tibet Chicken Probiotics And Rhodiola On Growth Performance, Ascites Susceptibility And Intestinal Function Of Broilers

The overuse of antibiotics in animal production could pose a significant threat to food safety and public health. Thus, in order to reduce the antibiotic application, effective alternatives to antibiotics are urgently needed to maintain current animal production levels and health. Probiotics can be considered as a possible alternative to antibiotics. In the process of selecting animal probiotics, antibiotic resistance of probiotic strains is often neglected, so that the potential risks exist in its practical application. One objective of this study was to isolate, characterize and select lactic acid bacteria strains from the gastrointestinal tract of Tibet chickens which presumbably have lower antibiotic resistance, and further investigate its effect on growth performance and gut barrier of chicken. Our study also determined the effects of Rhodiola on production performance and health parameters of broilers raised at high altitude. The results from these studies would provide scientific evidence for the application of probiotics and Rhodiola in poultry production. The results for four experiments were shown as follows:In the first experiment, 113 lactic acid bacteria(LAB) strains were isolated from the gastrointestinal tract of Tibet chickens raised in Tibet. Lactic acid bacteria were isolated using a Man-Rogosa-Sharpe(MRS) medium and confirmed by Gram stain and catalase identification. Sixteen LAB strains showed high acid and bile tolerance. Each LAB strain was scored according to the results of acid, bile and heat tolerance, antimicrobial activity against selected enteric pathogens, adhesion to intestinal cells and aggregation. Among 16 LAB strains, LTC-55(Lactobacillus salivarius) and LTC-113(Lactobacillus plantarum) strains were selected for further in vivo studies because of their high score(21 and 23)..In the second experiment, 360 healthy Arbor Acres broilers were randomly allocated by body weithgt(BW) to 4 experimental treatments according to a completely randomized design. The control birds were fed the basal diet alone while birds on other treatments received the basal diet supplemented with 50mg/kg of aureomycin, 109cfu/kg LTC-55 or 109cfu/kg LTC-113. The two LAB strains were fermented and dry-freezed into powder before adding to the feed. The effect of dietary supplementation of different probiotic strains was investigated for production perfermance, intestinal morphological structure and digestive enzyme activities. There were no significant differences in average daily gain(ADG), average daily feed intake(ADFI) and feed conversion rate(FCR) of broilers during 1 to 21 d among different treatments(P>0.05). However, during 22 to 42 d and 1-42 d, ADG and FCR were improved in broilers fed diets supplemented with probiotic strains LTC-55 and LTC-113 compared with the control group(P<0.05). There was no difference between probiotics groups and the antibiotic group(P>0.05). The BW of 42-d-old broilers were significantly higher in the LTC-55 and LTC-113 groups compared with the control group(P<0.05), which was similar to the antibiotic group. In additon, broilers fed LTC-55 had higher lipase activities on days of 28 compared with other groups(P<0.05). The probiotic strains and antibiotic treatment improved the duodenum development on days of 14, 28 and 42(P<0.05).The third experiment was designed to investigate the effect of probiotics on Salmonella induced intestinal epithelial barrier disruption and its molecular mechanisms. Eighty 1-day-old healthy male Nick chicks were randomly allocated into 4 experimental treatments:(i) the negative control(no probiotics treatment and no Salmonella infection),(ii) the probiotics treated group(109 Lactobacillus plantarum LTC-113),(iii) the Salmonella-infected group(109 Salmonella Typhimurium CVCC542), and(iv) the probiotics-treated and Salmonella-infected group(109 Lactobacillus plantarum LTC-113 and 109 Salmonella Typhimurium CVCC542). Compared with the negative control group, Salmonella infection significantly increased the intestinal permeability, decreased m RNA expression level of ZO-1 and CLDN-5, and increased CLDN-2 m RNA level at 8 hours post infection(P<0.05). However, the changes due to Salmonella infection were eliminated by probiotics treatments. Meantime, probiotics treatments significantly decreased the Salmonella numbers in the liver, spleen and cecum(P<0.05). Treated with probiotics significantly increased the m RNA expression level of ZO-1 in comparison with negative control and Salmonella infection group(P<0.05), but have no effect on the intestinal permeability(P>0.05).The fourth experiment was designed to investigate whether Rhodiola crenulata(R. crenulata) could alleviate the negative effects of hypoxia on broiler chickens reared in Tibet Plateau. The effect of supplementing crushed roots of R. crenulata on production performance, health and intestinal morphology in commercial male broilers was investigated. Dietary treatments included CTL(basal diet), Low-R(basal diet + 0.5% R. crenulata) and High-R(basal diet + 1.5% R. crenulata). In comparison with broilers fed the control diet, Low-R had no effect on production performance(P>0.05) while High-R significantly decreased average daily feed intake at d14, 28 and 42, body weight at d28 and 42 and gut development(P<0.05). Ascites induced mortality did not differ among treatments(P>0.05). Nevertheless Low-R significantly reduced non-ascites induced mortality and total mortality compared with broilers fed CTL and High-R diets(P<0.05). Broilers fed the High-R diet had significantly increased blood red blood cell counts and hemoglobin levels at 28 d compared with other treatments(P<0.05).In conclusion, we successfully isolated and screened 2 LAB strains with good probiotic properties from Tibet chickens. Dietary supplementation with 2 lactic acid bacteria strains in broilers diet could improve intestinal digestion and absorption function; consequently enhance production performance, similar to the antibiotic treatment. In addition, 2 lactic acid bacteria strains could protect newly hatched chicks from Salmonella induced intestinal epithelial barrier disruption by stabilizing the expression of tight junction genes or decreasing the Salmonella colonization. Supplementation with Rhodiola could decrease mortality rate amd might reduce the effects of hypoxia on broilers reared at high altitude in Tibet.