Strategies for mastitis control: dry cow therapy and culling

SUMMARY The effects of three selection strategies for dry cow therapy on prevention of new infections and rate of antibiotic usage were compared. Quarter infection status of 1044 cows in 12 herds was determined by bacteriological methods at drying off, calving and three to five months into the following lactation. Cows that were uninfected at drying off were randomly allocated to treatment (whole udder, dry cow therapy) and non-treatment groups. Infected cows were randomly allocated to whole udder or infected quarter only treatments. The strategies compared were blanket treatment (treat all quarters of all cows), selective cow treatment (treat all quarters of any cow infected in one or more quarters) and selective quarter treatment (treat infected quarters only). Selective cow treatment was identified as the preferred strategy. Blanket treatment resulted in increased antibiotic usage (15.5 vs 6.4 tubes per infection eliminated) with no additional benefit, and selective quarter treatment resulted in a higher new infection rate (6.4%vs 3.9% quarters) in the dry period. The prevalence of infection within a herd at drying off had no influence on new infection rates in the dry period or early lactation. The cure rate after dry cow treatment (mean of 66%) decreased significantly with increasing age (P < 0.001). Cows infected in the previous lactation contributed over 76% of infections at calving and nearly 70% at mid-lactation. To lower the incidence of mastitis in a herd, a greater emphasis on culling of older infected cows and prevention of new infections during lactation is needed.     

Management of the dry cow in control of peripartum disease and mastitis.

The dry period has great implications on overall health and productivity in the subsequent lactation. Many anatomic, physiologic, and immunolgic changes are occurring for both the cow and the mammary gland during this time. These changes need to be understood and taken into consideration when assessing and implementing health management programs that involve this crucial time period. Specifically, nutritional and immunologic requirements of the individual cow need to be considered. The occurrence of many peripartum diseases is significantly influenced through nutritional and metabolic parameters that can be strongly influenced, controlled, and monitored in the dry period. From an udder-health perspective, the goal of the dry period can be met by recommending administration of DCT to all quarters of all cows at the end of lactation. As research continues to explore and define shortcomings of this approach and as scrutiny of the prophylactic use of antibiotics increases, however, novel approaches to preventing and eliminating IMI may become more readily available. These approaches offer new methods to improve upon and redefine what should be realistic goals of the dry period and afford an opportunity for continued improvement of udder health in today's dairy herds.     

Within herd comparison of teat dipping and dry cow therapy with only selective dry cow therapy in six herds

A within herd comparison of teat dipping and dry cow therapy (full treatment) with only selective dry cow therapy (partial treatment) was carried out in six commercial dairy herds for a two year period. In four herds, the incidence of clinical mastitis was 2 to 12 per cent higher in the partial treatment group. In another herd, in which the pattern of clinical mastitis isolates was unusual in that minor pathogens were isolated from 30 per cent of mastitis cases, the incidence was 43 per cent higher in the partial treatment group. In the remaining herd the incidence was 10 percent higher in the full treatment group. Streptococcus uberis mastitis was more common in the partial treatment groups of five herds; coliform mastitis was more common in the full treatment groups of two herds and similar in both groups in the other herds. High rates of coliform mastitis were associated with poor herd environmental conditions but this was not true for Strep uberis mastitis. Rates of staphylococcus aureus and Strep dysgalactiae mastitis were low in all herds. The level of major pathogen infection in cows completing the trial in all herds increased in the partial treatment group from 5 per cent of quarters at the start to 12 per cent at the finish of the trial. In the full treatment group, however, there was only a small increase in this level. In contrast, levels of Corynebacterium bovis infection increased by 17 per cent in both treatment groups. Continued use of teat dipping and dry cow therapy was associated with a higher rate of coliform mastitis in two of the three herds where there were poor standards of hygiene and husbandry.     

Mycoplasma californicum mastitis in the dry dairy cow

Mastitis in 85 of 140 dry cows and 16 of 101 milking animals on one farm was shown to be caused by Mycoplasma californicum. The infection was eradicated from the herd over a five month period by a combined programme of identification, segregation and culling of infected animals. Some dry cows produced a self-cure, but the majority calved with nonfunctional quarters which produced very little colostrum and resulted in a high incidence of calf mortality. The source of the infection could not be established, but it was probably spread in the dry cows by the unhygienic application of long acting intramammary antibiotic therapy.     

A comparative field trial of cephalonium and cloxacillin for dry cow therapy for mastitis in Australian dairy cows

OBJECTIVE: To investigate and compare the therapeutic efficacy of dry cow agents containing either cephalonium or cloxacillin within Australian dairy herds. DESIGN: A treatment-control trial. METHODS: Milk from infected quarters of cows with high somatic cell counts in milk on eight Australian dairy farms was cultured to identify bacterial pathogens. Cows were randomly assigned to treatment groups and one group was treated with cephalonium at drying off and the other group was treated with cloxacillin at drying off. Milk samples from infected quarters were collected immediately after calving and were cultured for pathogens. The effect of treatment on bacteriological cure was examined and somatic cell counts from infected cows from the first two herd tests after calving were examined for a treatment effect. On four farms, milk samples were collected for culture from all cases of clinical mastitis identified within the first 7 days after calving. The effect of treatment upon incidence of clinical mastitis after calving was examined. RESULTS: There was no significant difference between treatments on quarter cure rates for new infections, for chronic infections and for infections with Staphylococcus aureus, Streptococcus agalactiae and Streptococcus uberis. Infected quarters treated with cephalonium had a significantly higher cure rate than quarters treated with cloxacillin when Corynebacterium bovis and Staphylococcus epidermids were included as pathogens combined (80.3% versus 70.7%). There was no significant difference between the treatments on somatic cell counts of infected cows at the first two herd tests after calving. There was no difference between treatments on the incidence of clinical mastitis in the first 7 days after calving.     

Methods of diagnosing subclinical mastitis in dairy cow mastitis control programs

The number of somatic cells and the isolation of the causative agents of mastitis in quarter, composite, bucket, and bulk tank samples of cow's milk was determined four times during a six-month period. The number of somatic cells in milk samples indicated a degree of mastitis infection and was influenced neither by the year season nor by the length of lactation. At a repeated examination of 28 dairy cows an increased number of somatic cells in milk was found once in 68 udder quarters and with three successive samplings only in 21 quarters. The etiological agents of mastitis were detected once in 31 quarters and three times in succession only in five quarters. The number of cows positive by the number of cells in quarter samples of milk increased from 52.9-58.8% at a single examination to as much as 100% at four examinations. The etiological agents of mastitis were isolated in a single examination in 17.6% of cows and at four examinations in 58.8% of cows. The composite and bucket samples of milk containing 200 to 300 thousand cells per ml are recommended to be considered as mastitis-positive: in 68 to 78% they came from cows having more than 500 thousand cells per ml at least in one quarter sample. The number of cells in a bulk sample was in correlation with the percentage of cows having a positive NK-test (similar to CMT) and positive isolation of S. agalactiae from quarter milk samples.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dry cow intramammary therapy on quarter infections in the dry period

Quarter milk samples were taken from 150 cows from three dairy farms in south-east Queensland at drying off, two, four and six weeks after drying off, at calving, and one, two and three weeks after calving. In each of the herds, the cows were randomly allocated to three groups of approximately equal size. One group had all the quarters of all the cows treated at drying off with a dry cow antibiotic infusion containing cloxacillin; the second group was given no treatment, and the third group had selected quarters treated on the basis of their high activity of N-acetyl-beta-D-glucosaminidase at drying off. Dry cow treatment resulted in a marked reduction in the number of infected quarters at two and four weeks after drying off, so that the comprehensively treated group had significantly less infected quarters at these times (P<0.02). Twelve dinical cases of mastitis were detected two weeks after drying off in the untreated groups, 10 in the untreated quarters of the selectively treated groups, and no cases in the comprehensively treated groups. These cases were due mainly to Streptococcus uberis and Streptococcus dysgalactiae. The number of infected untreated quarters increased markedly between drying off and two weeks later, but in all three groups there was a marked decrease in the number of infected quarters between six weeks after drying off and calving, suggesting that the mammary glands were more able to overcome infections at this time.     

Recurrent coliform mastitis in the dairy cow.

Daily monitoring of milk over a 120-day period for bacteria and neutrophil counts revealed that following experimental E coli mastitis, five out of 28 infections resulted in the development of a long continued and recurring condition. Intermittent periods of acute inflammation were observed in the gland, pyrexia was noted, and if bacteria were isolated they were always of the same serotype as the original infecting strain. Failure to isolate bacteria and the lack of overt inflammation during periods of remission suggested that the bacteria were not in the gland cistern but within gland tissue. In one animal antibiotic therapy with a drug which was active in vitro was ineffective in vivo. However another antibiotic proved effective.     

克炎晶对奶牛乳房炎的治疗试验

使用克炎晶采用不同给药途径、不同剂量、不同疗程,对24例临床型乳房炎患牛和8例隐性乳房炎患牛进行了分组治疗试验。结果表明,每千克体重使用克炎晶0.5～1.0mg1～2次就能有效杀灭隐性乳房炎致病菌;对于临床型乳房炎,每千克体重0.5～1.0mg剂量总有效率为60%(9/15),而1.5mg总有效率为88.9%(8/9)。乳区基部注射总有效率为77.8%(7/9);乳池内注入总有效率为88.9%(8/9);肌肉注射总有效率为33.3%(2/6)。因此,临床治疗时应选择每千克体重1.5mg作为用药剂量,乳房基部注射和乳池内注入作为用药方法,疗程为3～5d。     

Crossed immunoelectrophoretic analysis of the antibody response in heifers and dry cows to Peptococcus indolicus in experimental and natural heifer mastitis and dry cow mastitis

Crossed immunoelectrophoresis with intermediate gel was used to investigate the antibody response of experimentally infected heifers and of naturally infected heifers and dry cows at grass with mastitis against soluble extracellular antigens of Peptococcus indolicus. Using both precipitin titres and precipitin scores (the sum of precipitin titres against individual antigens) rising titres of antibodies against antigend of P. indolicus were demonstrated in sera from experimentally infected pregnant and non-pregnant heifers. Statistically significant differences in precipitin scores against extracellular antigens were also shown between pregnant heifers with mastitis and healthy pregnant heifers and between dry cows with mastitis and health dry cows. The biochemical nature of the principal reactive antigens was not elucidated. These serological investigations lend strong support to the pathogenic role and significance of P. indolicus in mixed infections with Corynebacterium pyogenes in the aetiology of heifer and dry cow mastitis.     

奶牛乳腺炎的防治与研究动态

奶牛乳腺炎是由病原体侵染奶牛的乳腺而引起的一种疾病,病原复杂多变,但临床感染主要以葡萄球菌、链球菌、大肠杆菌、支原体、放线菌等多见。奶牛乳腺炎是影响奶牛业发展的头号疾病,引起了众多国家科研工作者与政府的高度重视。本文就奶牛乳腺炎的发病机制、病原学、诊断方法、治疗手段及其综合防治等方面做一阐述。