| Among all animal needed trace elements,zinc plays a major role in animal immune system by providing nutrition and antagonizing of pathogens.The transformation of inorganic zinc into organic zinc is the first step of digestion and absorption.Furthermore,trace elements and probiotics may also benefit each other in this process.This study focusing on the Preparation of Zinc-enriched Probiotics and their role in disease resistance and immune function were analyzed.Detailed studies are as follows:(1)Preparation of zinc-enriched probiotics.The fermentation of zinc-enriched probiotics from inorganic zinc by using Lactobacillus acidophilus,Candida utilis and Bacillus coagulans,and the fermentation conditions for preparation of zinc-enriched probiotics were optimized;The results suggested that the optimized fermentation condition was as follows: the ratio of zinc sulfate solution to solid fermentation medium of bacteria mix was 1: 200,the inoculum size of mixed seed solution was 5%,the fermentation temperature was 35?,the culture time was 36 hours,the drying temperature was 60?;the total viable count of zinc-enriched probiotics was 9.07×109 cfu / g,the organic zinc-enriched conversion rate was 76.82%,and the animal experiment proved it to be safe.(2)The effects of zinc-enriched probiotics on production performance in laying hens.0.2% zinc-enriched probiotics addition significantly(P <0.05)increased the average daily egg production,egg production rate,average egg weight,egg shell thickness,egg shell strength,huff units;while significantly(P <0.05)reduced egg yolk cholesterol and soft shell egg rate.The number of blood hemoglobin(HGB),white blood cells(WBC),red blood cells(RBC)were increased;The contents of triacylglycerol(TG),total cholesterol(TC),glutamic-oxaloacetic transaminase(GOT),Serum total protein(TP),serum albumin(ALB),alkaline phosphatase(AKP),Ca2+ and inorganic P,luteotropic hormone(LH),estradiol(E2),triiodothyronine(T3)and tetraiodothyronine(T4),progesterone(P),insulin-like growth factor-1(IGF-1),follicle stimulating hormone(FSH),glutathione peroxidase(GSH-Px),total antioxidant capacity(T-AOC)and total superoxide dismutase(T-SOD)activity were increased.The contents of blood glucose(GLU),uric acid(UA),adrenocorticotropic hormone(ACTH)and malondialdehyde(MDA)were decreased.(3)Effects of different zinc-enrichment levels on the immune function of laying hens.The results showed that: increased the spleen index,bursa index and thymus index of egg chicks,increased the level of IL-2 and IFN-? in serum,increased the transformation rate of peripheral blood T lymphocytes and ND,AI antibody levels after immunization.Zinc-enriched probiotics inhibited the infection of Escherichia coli(E.coli).the incidence of E.coli was reduced by 40.00% and the mortality rate was reduced by 68.12% compared with the positive control group.The incidence of Salmonella pullorum was reduced by 42.79% and the mortality rate decreased by 62.49%;the incidence of Staphylococcus aureus decreased by 46.67% and the mortality rate was decreased by 66.67%.16S r DNA sequencing showed that the number of microbial populations in the cecal was significantly increased in probiotics addition group,while the pathogenic microbial population was decreased significantly lower.The results showed that the number of Lactobacillus in the group treated with the zinc-enriched probiotics was 9.41% higher than that of the control group(P<0.05),and the number of Bifidobacteria was 7.63% higher than that of the control group(P<0.05).The average decrease of Bacteroides was 4.76%(P> 0.05),and the average level of E.coli was decreased by 3.70%(P>0.05),Enterococcus was decreased by 12.12%(P<0.05)compared with the control group.Staphylococcus aure was lower than the control group by 23.73%(P<0.05).In summary,zinc-enriched probiotics not only contribute to the growth of laying hens and improved the performance of the laying hens,but also improve the physiological and biochemical indexes of the layers and the antioxidant capacity.It is possible that zinc-enriched probiotics improve the immune organ index of laying hens,promote the secretion of cytokines that regulate immunity and enhance the number of beneficial bacteria in the intestine of laying hens,which may be the main mechanism of their function. |
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