| With the development of animal husbandry, the bacterial resistance increase leaded to the overuse of antibiotics, the increased farming costs and drug residues attracted widespread attention, and some countries restricted the type, usage, dosage and otherions of antibiotics.Therefore, a new alternative to antibiotics, antibacterials without residual, toxic, and side effects, the probiotics in the production was used more and more common. With improving the in vivo environment, reducing drug residue, regulating gastrointestinal balance, enhancing immunity and reducing preverence of diseases, probiotics have become the new alternatives to antibiotic used by many countries, and the fourth category of feed additives following the vitamins, trace elements and amino acids. In probiotics, the active agents of lactic acid bacteria was most widely used. In this paper, one Lactobacillus plantarum(L. plantarum) was isolated and identified from the intestinal of healthy duck, antibacterial test in vitro and the effects on meat ducks production performance and immune function of the isolated L.plantarum strain were studied. The test is divided into two portions.Test one: Isolation and antibacterial test in vitro of L. plantarumTwo bacteria strains were isolated from the cecal contents of a 20-day-old duck with MRS medium, and the two isolated strains with producting significant dissolved calcium ring in were proved to be a L. plantarum strain and a Lactococcus lactis strain by molecular identification. By bacteria plate count method, the isolated L. plantarum strain had different degrees of inhibition to Lactobacillus Proteus mirabilis, Escherichia coli, Klebsiella pneumoniae, Shigella sonnei, Staphylococcus aureus, Salmonella, Serratia marcescens and anatipestifer. With 4% dose of the metabolite of the isolated L. plantarum strain, the inhibition rates were 33.00%, 28.47%, 29.27%, 37.84%, 22.30%, 79.52%, 20.62% and20.00% to these pathogens, respectively, while the inhibition rates were 78.60%, 54.14%,68.97%, 77.78%, 84.21%, 96.77%, 77.64% and 66.00%, respectively, with 10% dose of the metabolite of the isolated L. plantarum strain. The isolated L. plantarum strain had the most significant inhibition effect to Salmonella, and had over 50% inhibition rate to all the eight pathgens with 10% dose of the metabolite.Test II: The effects on meat ducks’ production performance and immune function of the isolated L. plantarum strainThe isolated L. plantarum strain was cultrured to a solution of 5.475 × 109 CFU/ml. All of 120 1-day-old ducks were randomly divided into two equal groups. The two groups of ducks were feed with the same management by free way of drinking water and eating feed,and the ducks of the experimental group were feed with the water added with 1% of the fermentation of the isolated L. plantarum strain. The results showed that the weight gain in one week of experimental group is larger than that of the control group, and the difference of the two groups was more and more between 14 to 28 days for growing discrepancy, up to 35 days, the experimental group remained significantly higher than the control group(p <0.05).The meat feed ratio of the control group was higher than the experimental group before 14day-old, while the meat feed ratio of the experimental group was higher than that of the control group at 21 days of age, and was significantly higher than the control group(p <0.05)at 35-days-old. The thymus index, spleen index and bursa of Fabricius(BF) index of the experimental group were higher than the control group in whole experimental period. At 28-day-old, the thymus index and BF index showed the biggest difference(p <0.05), and the thymus index and BF index of the experimental group were higher of 33.80% and 18.67%than that of the control group, respectively. At 21 days old, the spleen index of the experimental group was 18.93% more than that of the control group, and showed the maximum difference(p <0.05). During the trial period, the thickness of the ileum and cecum wall and the hair length of the experimental group were higher than that of control group, and showed significantly different(p<0.05) at 35 days of age. In the cecal contents, the number of E. coli of the experimental group was less than the control group, while the number of Lactococcus was higher than that of the control group, especially in 20 days old.Feeding tests showed the metabolites of the isolated L. plantarum strain can inhibit the growth of the harmful bacteria and the L. plantarum can adjust the balance of intestinal flora duck, change the intestinal structure, promoting duck growth, improve and promote the growth of meat feed ratio and immune organs development, enhance the immunity of ducks.The results provided a theoretical basis of the L. plantarum for prevention and treatment for duck diseases and development and application of probiotics. |
PDF Full Text Request