The Epidemiological Investigation And Major Pathogen Isolation, Identification And Drug Susceptibility Testing Of Subclinical Mastitis Cows In Yangling

In recent years, due to the rapid development of dairy cow breeding, unscientific feeding management as well as disease prevention and control technology, cow mastitis become a common and frequently-occurring disease, which resulted in a decline in milk production of dairy cows and low quality of milk. This endangered the development of dairy industry. In order to reduce the incidence of mastitis in dairy cows to increase their milk production, 100 cows in Yangling and its surrounding areas were conducted investigation,and the isolation, identification and drug susceptibility test of major pathogens for recessive mastitis. The following results were obtained:Experiment one:1. Results of LMT test showed that, the positive rate of recessive mastitis of the investigated cows was 55.00%, and the positive rate of milk area was 49.81%.2. The recessive mastitis incidence of cows in the farm varied with the seasons with a peak occurred in summer (71%), it had a significant difference with indices of the other seasons (P<0.5).3. There was highest incidence in left front milk area for the tested cows in the farm, i.e., 53.41%, but there was insignificant difference among the four milk areas.4. Among the tested dairy cows, the disease incidence of the first four parturition increased with the order of the fetus decreases. There was an increasing trend of incidence when the fetus order was larger than four. No significant differences were found when the fetus order were 2 and larger than five (P>0.05), having a significant difference with the other order of fetus (P<0.05).5. During lactation period, the difference of the positive detection rates of subclinical mastitis in January and February were most significant (P<0.01) among the twelve months, then there was an increasing trend of it when lactation months increased. The incidence was 68.00% for daily milk production below 20 kg, which was significantly higher than that for daily milk mass over 20 kg (42.00%, P<0.05%). Experiment two: 1. Among the tested 71 samples in the 100 milk samples in the second season, three major pathogens, total of 58 isolates, were isolated, among which, 41 were Staphylococcus aureus, accounting for 70.69% of the isolates, 14 were Streptococcus, accounting for 24.14% of the isolates, 3 were Escherichia coli, accounting for 5.17% isolates.2. Among the 58 positive milk samples, 23 were individually infected by pathogen, accounting for 39.66% of the total, 16 were infected by S.aureus, and 7 were infected by Streptococcus, 35 were mixed infected, accounting for 60.34% of the total. Mostly the infections were caused by combined infections of S.aureus and Streptococcus. And the isolated E.coli were all combined infections with Staphylococcus aureus and Streptococcus.3. The results of the drug susceptibility test showed that S.aureus was highly sensitive to ceftazidime, ciprofloxacin, broclin and gentamicin, and can resist chlortetracycline, erythromycin and furazolidone to some different extents. Streptococcus was highly sensitive to ceftazidime, ciprofloxacin, and can resist gentamicin, erythromycin, chlortetracycline and furazolidone to different extents. E.coli was highly sensitive to ceftazidime, ciprofloxacin, and broclin, and can resist gentamicin, erythromycin, tetracycline and furazolidone to different extents. These three major pathogenic bacteria can totally resist ampicillin with a resistant rate of 100%.