Some Biological Characteristics Of Lactobacillus Casei And Its Effects On The Growth Performance And Major Immunity Function Of Broilers

Probiotics, a class of general living microorganisms which are beneficial to the host organism. They can Promote the body’s growth and development, and prevent the occurrence of disease by maintaining the balance of intestinal flora, competing adhesion sites with pathogens、secreting antimicrobial substances、enhancing the epithelial barrier, regulating the intestinal immune responses. At present, probiotics have been widely used in livestock and poultry breeding as feed additives. In this test, the bacteriostatic activity and coherent ability for intestinal cells of lactobacillus casei ATCC393 were studied, and the effects of L.casei and antibiotics on the growth and main immunity function of broilers were compared via adding them in drinking water. Through these assays, to evaluate the application value of the L.casei and provide theoretical and experimental basis for the application in broiler breeding.The vitro bacteriostatic experiment proved that bacteria liquid of L.casei and their metabolic products could produce the growth of Enterotoxin Escherichia coli, salmonella and staphylococcus aureus, all have significant bacteriostatic effect. The effect of bacteriostasis show that E. coli > staphylococcus aureus > salmonella. However, the bacteriostatic effect of L.casei thallus on these pathogenic bacteria is not significant. The adhesion characteristics of Lactobacillus casei to Intestinal epithelial cells, and its inhibitions on adhesion of Enterotoxigenic Escherichia coli(ETEC) K88 to Intestinal epithelial cells were assessed by co-culturing between L.casei, ETEC K88 and Caco-2 cells. The results indicated that L.casei and ETEC K88 could adhere to Caco-2 cells, with the increase of concentrations and incubation time of bacterias, the number of bacterias adhered to each cell increased significantly(p<0.05). Moreover, L.casei can inhibite the adhesion of pathogenic ETEC K88 to Caco-2 cells, the inhibitory ability related to the concentration and adding order of bacterias.160 one-day-old broilers were randomly divided into 4 groups with 4 replicates in each group and 10 chickens per replicate: the control group(group A) which drinking normal water, the L.casei group(group B), the fosfomycin group(group C) and the florfenicol group(group D) which adding 1 g/L L.casei, 0.1% fosfomycin and 0.1% florfenicol in drinking water respectively. The test cycle was 21 days and divided into three phases. The average daily gain, feed weight ratio, immunity organ index, IgG content, sIgA content, and lymphocyte proliferation ability of the treatment group were detected at different stages. The results showed that the effect of body weight, average daily gain and average daily feed intake was not significant by adding L.casei and fosfomycin in drinking water, but the trend was rising, the growth performance of broilers was significantly inhibited by adding florfenicol(p<0.05), the effect of all on chicken feed weight ratio was not significantly. Intestinal flora test results showed that L.casei can promote the proliferation of intestinal lactobacillus, but the inhibitory effect on E.coli, salmonella is not obvious, fosfomycin and florfenicol inhibited the proliferation of intestinal flora. The effect of L.casei on immunity organ index was not significant, but the IgG content, sIgA content and lymphocyte proliferation ability were significantly increased(p<0.05), fosfomycin could improve the immunity function of broiler also, but the differences were not significant, immunity function was significantly inhibited using florfenicol(p<0.05).In conclusion, L.casei ATCC393 can produce antibacterial substances inhibiting the proliferation of E.coli, salmonella, staphylococcus aureus, and can adhere to the surface of intestinal epithelial cells to inhibit the adhesion of Pathogenic bacteria. L.casei can significantly improve the content of lactobacillus in the gut and can significantly improve the immunity function of broilers after feeding via rinking water. The effect of antibiotics on immunity function is not consistent, florfenicol can inhibit the immunity function of broilers, but fosfomycin is adverse. Therefore, we should minimize the use of antibiotics in feed additives of broilers, and raise the use of probiotics by improving the fermentation process, in order to improve the growth performance and disease resistance of broilers, and obtain greater economic benefits.