| Dairy cow mastitis is an udder inflammation caused by physical, chemical or microbial factors stimulation, and the pathogenic microbe infection is the major cause of the disease which is extensive around the world and has very high incidence. Mastitis not only bring huge economic losses of dairy cow production, but also do harm to dairy industry, public health and food safety.The pathogen of cow mastitis which was caused mainly by bacterium is complex. There are so many different microorganisms having been isolated from bovine intramammary infections (IMI), which mainly including the staphylococci (mostly S. aureus), enterococci (mostly E. faecalis), and streptococcal species (S. agalactiae, S. dysgalactiae subsp. dysgalactiae, and S. uberis ) and so on, that it is much more difficult in the prevention and treatment of the mastitis. Generally speaking, there are many disadvantages about the treatment of antibiotics after the occurrence of mastitis at present, by which the decreased milk production or even stopping milk is caused, and the residues in milk is also harm to the human beings. So, it is very important to find a new drug without residues in the milk to control the cow mastitis one of which is the Egg-yolk antibody.Egg yolk immunoglobulin is Egg-yolk antibody, also called IgY, is principal classes immunoglobulins in avian sera. IgY can combine to specific antigens such as bacteria, viruses, carcinogens and toxins, it can also neutralize the harmful effects of the antigens. It is similar between the placental transfer of IgG in mammals and the major serum antibody in chickens (IgG) being transferred across the follicular epithelium of the ovary and accumulated in the yolk during oogenesis. The difference is that the use of chickens for specific immunoglobulin production is much more convenient.First of all, the subjects of dairy cow mastitis from a dairy farm in Lanzhou, and the 44 samples from the milk of the cattle infected were collected. Isolation, Identification and drug sensitivity test of the main pathogenic bacteria were made. Specific IgY was produced by immunizing laying hens with the mixture of the isolated pathogens-- S.saureus and E.coli, and detect the content of specific IgY and antibacterial test. Egg yolk antibodies were separated and purified by Cold ethanol and PEG-6000 method. Titer of this antibody and antibacterial test in vitro was determined respectively by enzyme-linked immunosorbent assay (ELISA) and liquid medium turbidimetry method.The results were as follows:1.The results were showed that the mastitis of the cows were mainly caused by Staphylococcus ,Streptococcus and Escherichia spp , 79 bacterias were isolated from milk samples, of which thirty five strains of Staphylococci aureus and Staphylococcus epidermidis(44.3%), results-type information trains of Streptococcus bovis(25.3%) and 11 strains E.coli(13.9%)were detected .Those pathogens were susceptible to Ampicillin, Norfloxacin, Sepctinomycin, Amoxicillin and novobiocin and so on, however , resistant to Penicillin G , streptomycin and Sulfurmethoxazole.2. The highest titer of the multi-valent antibody was 4.71 log. The data from the inhibition in vitro studies demonstrated that the growth of both S.aureus and E.coli can be inhibited either in solid or liquid culture. The Minimal Inhibitory Concentration (MIC) of IgY was detecteced as 35 mg/mL in liquid medium.In this study, the main pathogenic bacteria causing dairy cow mastitis at the farm had been successfully isolated and identified, and the High-activity-specific egg-yolk antibodies were also produced, which provide some control reference for dairy cow mastitis at the farm.
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