Genomic Characteristics Of Lactobacillus Rhamnosus CLK101 And Effects Of Its Feeding On Nandan-Yao Chicken

The overuse of antibiotics has led to an increasing number of pathogenic bacteria with antibiotic resistance in the natural world,exacerbating the risk of infectious diseases and deaths in both humans and animals over time.Therefore,it is urgent to explore safe,natural,and economical alternatives to antibiotics.Currently,several studies have shown that probiotics can be widely used as alternatives to antibiotics in agriculture and animal husbandry.Probiotics can help improve the growth performance of poultry and feed utilization.By colonizing the poultry’s gut,they can effectively improve and maintain the ecological balance of the poultry’s gut microbiome,making them beneficial for poultry.Among them,Lactobacillus rhamnosus is a type of probiotic that can tolerate the acidic environment of the digestive tract and colonize the host’s gut environment.It can regulate the gut microbiome and improve immunity,making it a target of interest for researchers.This bacterium can secrete relevant metabolites in the host’s body to inhibit the growth of pathogenic bacteria and promote the growth of beneficial bacteria,which cannot be underestimated.In this experiment,the Lactobacillus rhamnosus CLK101 strain was used as the research object for genome analysis and annotation,aiming to understand the genetic basis of its probiotic properties.Research was also conducted on the Nandan-Yao chicken to investigate the effects of Lactobacillus rhamnosus on the chicken’s production performance,organ-related indices,serum immunity indicators,and gut diversity during the feeding process.This research can provide a foundation for healthy breeding of the Nan Dan-Yao chicken.The main research contents are as follows:(1)The complete circular chromosome of Lactobacillus rhamnosus CLK101was sequenced using both Nanopore third-generation sequencing and second-generation sequencing technologies.The chromosome is 2,937,234 bp in size with a GC content of 46.71%,and it encodes a total of 2,851 genes,including61 t RNAs and 15 r RNAs.Gene annotation and analysis showed that the genes encoding carbohydrate transport and metabolism were the most abundant,with genes related to adhesion proteins,immune regulation,and other beneficial genes.The study results showed that Lactobacillus rhamnosus CLK101 contains genes related to genetics and metabolism,as well as strain-specific genes.This further confirms that Lactobacillus rhamnosus CLK101 is a potentially beneficial microorganism with good safety.(2)The probiotic properties of Lactobacillus rhamnosus CLK101 in vivo were evaluated using 1-day-old Nandan-Yao chickens as experimental subjects.After 21days of feeding,the body weight of the two groups fed with Lactobacillus rhamnosus(1×10~6cfu/g,1×10~7cfu/g)was significantly higher than that of the oxytetracycline group and the blank control group(P<0.05).Feeding with Lactobacillus rhamnosus had a certain degree of influence on the digestive enzyme activity of the chickens,indicating that it could help Nandan-Yao chickens to better absorb and digest feed,and improve their growth performance.The ratio of villus length to crypt depth in the group fed with a low dose of Lactobacillus rhamnosus was higher than that in the blank control group,indicating that Lactobacillus rhamnosus has a promoting effect on chicken intestinal development and growth.Feeding with Lactobacillus rhamnosus can also enhance the immune function of Nandan chickens and protect the intestinal mucosal barrier,playing an important role in their immune and anti-inflammatory responses.(3)The microbiota of the cecum of Nandan-Yao chickens in the control group,antibiotic group,and two groups fed with different concentrations of Lactobacillus rhamnosus CLK101 were sequenced using 16s rDNA sequencing.At the phylum level,the dominant bacteria were Firmicutes,Actinobacteria,Proteobacteria,Bacteroidetes,and Actinomycetes.At the genus level,the relative abundance of Lactobacillus,a beneficial bacteria that can utilize sugars,was significantly increased by low-concentration Lactobacillus rhamnosus.High-concentration Lactobacillus rhamnosus significantly increased the relative abundance of Akkermansia,a beneficial bacteria that can break down polysaccharides.Therefore,feeding different concentrations of Lactobacillus rhamnosus can significantly enhance the metabolic capacity of Nandan-Yao chicken’s intestines for sugar substances and regulate the balance of the chicken’s intestinal microbiota.In summary,this study utilized genomic analysis techniques to annotate and analyze the genome of the Lactobacillus rhamnosus CLK101.Subsequently,in vivo and in vitro animal breeding experiments were conducted to evaluate its probiotic properties and safety.The results showed that this strain could serve as an alternative to antibiotics to improve the growth performance and immunity of the Nandan-Yao chicken.This study demonstrated the probiotic efficacy of Lactobacillus rhamnosus CLK101,indicating its promising application prospects in agricultural breeding,and providing theoretical value and practical guidance for the healthy breeding of meat chickens.