Screening Of Rabbit-derived Lactic Acid Bacteria And Evaluation Of Its Probiotic Potential

Intensive breeding leads to the frequent occurrence of digestive tract diseases and high mortality of rabbits.With the prohibition of antibiotics,the research and development of a new green and safe feed additive has become a research hotspot.Lactic acid bacteria are most widely used in livestock and poultry,and studies have shown that the positive effects of the strains derived from the intestinal tract of the same animal are far greater than that of the heterologous strains.Therefore,the purpose of this experiment is to screen out an excellent rabbit-derived lactic acid bacteria,and to explore its effects on the growth performance,meat quality,and intestinal microbial diversity of meat rabbits,and to explore its damage to meat rabbit tissues by establishing a LPS-induced stress model,Immunity and anti-oxidation effects,laying the foundation for the application of rabbit-derived lactic acid bacteria.The results showned as follows:Experiment 1:Isolation,identification and determination of biological characteristics of lactic acid bacteria from rabbitsThe adult rabbits(30 cases)with excellent growth performance were selected,the caecal contents as the starting bacteria source were separated and screened the acid production efficiency and antibacterial performance as the evaluation criteria.The target strain LC-6-2 was finally screened out.Morphological observation of the colony and bacteria combined with biochemical and molecular biological identification,finally determined that the strain is Pediococcus lactis.By measuring the growth characteristics of the strain,it was found that the strain reached the logarithmic phase at 6h and the stable phase at 20h under the condition of liquid culture(the concentration of the strain was 5.3×109 CFU/g).The pH value of the acid producing energy was 3.98 after 48h culture.The in vitro bacteriostatic test showed good inhibitory effect on pathogenic bacteria such as Escherichia coli,Salmonella,Lactobacillus singular and Staphylococcus aureus,and no hemolytic reaction was found.It is a potential strain as a good probiotics agent.Experiment 2:Effects of Petiococcus lactic from rabbits on growth performance,serum biochemical indexes,meat quality and intestinal microflora of meat rabbitsSeventy-two 42-day-old meat rabbit with healthy and similar weight(1.37±0.09 kg)were randomly divided into 3 treatment groups.Each group had 6 replicates with 4 rabbits per replicate,which were fed in single cages.The piglets in the CON group were fed a basal diet,and the piglets in the AB and PA groups were fed the basal diet supplemented with 15 μg/g aureomycin and 5×106 CFU/g Petiococcus lactis,respectively.There was a pretrial period of 7-day followed by an experimental period of 28-day.1)Compared with CON and AB groups,the ratio of feed to weight in PA group was significantly decreased(P<0.01);2)Compared with CON and AB groups,total protein content in PA group was significantly increased by 1.93%(P>0.05)and 5.51%(P<0.01),respectively;Compared with PA group,urea nitrogen content in AB group was decreased by 14.06%(P<0.05);Compared with CON group,the triglyceride and total cholesterol in PA group were decreased,but there was no significant difference between PA group and AB group(P>0.05);3)Compared with CON and AB groups,the L value of meat color in PA group was increased by 2.35%(P>0.05)and 14.68%(P<0.01),respectively;Compared with CON and AB groups,the drip loss and cooking loss in PA group were decreased(P>0.05).Compared with CON group and AB group,the muscle fiber diameter of PA group was the smallest;There was no significant difference in lipid deposition among all groups(P>0.05);4)Compared with CON group and AB group,pH of each intestinal segment in PA group showed a decreasing trend;5)Compared with CON and AB groups,the activities of trypsin and lipase in jejunum in PA group were significantly increased(P<0.01);6)There were no significant differences in the contents of total volatile fatty acids(TVFA),acetic acid and butyric acid among all groups(P>0.05),but compared with CON and AB groups,the contents of TVFA,acetic acid and butyric acid in PA group showed an increasing trend;7)There was no significant difference in jejunal villus height between PA group and CON group and AB group(P>0.05);Compared with CON group,jejunum crypt depth in PA group was significantly decreased by 7.48%(P<0.05),and the velvety crypt ratio was significantly increased by 8.06%(P<0.01);Compared with AB group,ileum villus height and velocious-secreting ratio in PA group were significantly increased by 3.63%and 5.46%(P<0.05),respectively;8)There were differences in cecal microbial diversity among experimental groups(P<0.05).The abundance and diversity of species added with PA increased,and the relative abundance of Ruminococcaceae,Unclassified Bacteria Genera of Trichelicaceae and Sinobacteriaceae in PA group was the highest,which was significantly different from that in CON group and AB group(P<0.01).Bacteroidetes in PA group was the lowest,and there was significant difference between PA group and the other two groups(P<0.05).Experiment 3:Effects of Petiococcus lactis from rabbits on tissue damage,antioxidant capacity and immunity of meat rabbits under conditionsOn the basis of experiment 2,the remaining meat rabbits were randomly divided into 4 groups with 8 rabbits in each group.The rabbits in CON and LPS groups were fed the basal diet,and the rabbits in LPS+AB and LPS+PA groups were fed the same diet as those in experiment 2.Rabbits in LPS,LPS+AB and LPS+PA groups were intraperitoneally injected with 200 μg/kg BW on day 28 and 31,respectively,and rabbits in CON group were injected with 0.9%normal saline on day 35,respectively,and were anaesthetized and slaughtered.1)Compared with CON group,villus height of jejunum in LPS group was significantly decreased(P<0.01),and there was no difference between LPS+AB group and LPS+PA group(P>0.05).The crypt depth and crypt ratio of jejunum and ileum in LPS group were significantly different from those in the other three groups(P<0.05),but there were no significant differences between CON group,LPS+AB group and LPS+PA group(P>0.01),and the wall thickness of jejunum and ileum in LPS group was significantly lower than that in the other three groups(P<0.01);2)After LPS stress treatment,compared with CON group,the-number of ileal epithelial cup cells in LPS group,LPS+AB group and LPS+PA group increased by 21.70%(P<0.01),8.13%(P>0.01)and 13.47%(P>0.05),respectively.The number of goblet cells in LPS+AB and LPS+PA groups was significantly lower than that in LPS group(P>0.05);3)The contents of ALT and AST in serum of LPS group were significantly higher than those of CON group,LPS+AB group and LPS+PA group(P<0.01).Compared with LPS group,PA+LPS group significantly improved the dilatation of hepatic sinuses and had a protective effect on liver.4)After LPS stress treatment,compared with CON group,serum CRP in LPS group,LPS+AB group and LPS+PA group was significantly increased by 35.42%(P<0.05),26.19%(P>0.05)and 32.61%(P<0.05),respectively;Compared with CON group,IgA content in LPS group was increased by 8.80%(P<0.05),and there was a decreasing trend in LPS+AB group and LPS+PA group;Compared with LPS group,IgA content in LPS+AB group and LPS+PA group decreased;Compared with LPS group,IgG content in CON group,LPS+AB group and LPS+PA group was significantly decreased(P<0.01);5)Compared with LPS group,DAO content in LPS+AB group and LPS+PA group was decreased by 1.69%and 1.54%,respectively(P>0.05);The serum CAT content in LPS+PA group was higher than that in LPS group,but the difference was not significant(P>0.05).Compared with LPS group,liver CAT content in LPS+AB group and LPS+PA group was increased by 17.24%(P>0.05)and 26.15%(P<0.01),respectively.MDA content in serum and liver of LPS group was significantly increased compared with other groups(P<0.05).In conclusion,the supplementation of Petiococcus lactis in the diet of meat rabbits can replace aureomycin to a certain extent,improve the growth performance,meat quality and cecal microbial diversity of meat rabbits;LPS stress can lead to tissue damage and reduced immunity of meat rabbits.The addition of Petiococcus lactis can improve the antioxidant capacity of serum,liver and intestinal mucosa,improve the growth performance and immunity of the body,reduce liver damage,improve intestinal morphology and structure,and then promote intestinal health of meat rabbits.