Correlations among the somatic cell count of individual bulk milk, result of the California Mastitis Test and bacteriological status of the udder in dairy cows

In a survey of about 3000 dairy cows producing low somatic cell count (SCC) milk and kept on a large-scale dairy farm, California Mastitis Test (CMT) positivity was found in 2714 udder quarters of 1491 cows. Pathogenic microorganisms were isolated from 57.6% of these 2714 udder quarters during bacteriological examination. The commonest pathogens were coagulase-negative staphylococci (CNS, 41%) and Staphylococcus aureus (32.5%); however, udder infections caused by environmental streptococci (12.8%) and coliform bacteria (6.8%) were also common. All pathogens resulted in a significant increase of the SCC in individual bulk milk (IBM) samples. In the case of CNS, this SCC elevation in IBM was significantly lower than in the case of infection by the other pathogens. In spite of this, because of the high number of udder infections caused by CNS, the adverse effect exerted by CNS on dairy herds is considered to be substantial. It was found that 54.6% of all CMT-positive cows produced IBM of an SCC below 400 thousand per ml. The milk produced by 41% of the 315 cows excreting S. aureus also had an SCC below 400 thousand per ml. This poses a serious risk of infection to the healthy herdmates. At the same time, 11% of the infected cows produced IBM with an SCC below 100 thousand per ml. On the basis of these findings, only the regular analysis of SCC of IBM can be a reliable indicator of chronic intramammary infection. As the SCC of milk produced by CMT-positive cows (and especially of those excreting pathogens) tended to increase with advancing lactation, the authors suggest that an efficient drying-off therapy should be used to restore udder health and, whenever justified, culling of cows cannot be avoided either.     

Lactoferrin concentrations in milk from normal and subclinical mastitic cows

The concentrations of lactoferrin (Lf) in quarter milk from normal lactating cows and subclinical mastitic cows were measured to determine whether the Lf concentration in milk is influenced by the age of the cow, the stage of lactation, number of milk somatic cells and the presence of pathogens. Lf concentrations in 111 quarter milk samples from 28 normal lactating cows and 270 quarter milk samples from 198 subclinical mastitic cows were measured by means of a single radial immunodiffusion test. Lf concentrations (means +/- standard deviations; logarithmic form) in normal cows and subclinical mastitic cows were 2.23 +/- 0.39 and 2.70 +/- 0.39, respectively. The mean milk Lf concentration (log) in subclinical mastitic cows was significantly (p<0.01) higher than that in normal cows. The mean milk Lf concentration (log) in normal lactating cows aged 5 years was lower than those in normal lactating cows aged 2 years (p<0.01) and 3 years (p<0.05). The results showed that the milk Lf concentration (log) is associated with age of the dairy cow (one-way analysis of variance test, p<0.01). The mean milk Lf concentration (log) in the latter lactational period tended to be higher than those in the peak and middle periods. Milk Lf concentrations (log) tended to be proportional to the level of the somatic cell count (SCC) score. Mean milk Lf concentrations (log) in subclinical mastitic cows infected with Staphylococcus aureus and with other streptococci species were significantly (p<0.01) higher than those in cows infected with coagulase-negative staphylococci and with Corynebacterium bovis.     

Prevalence of staphylococcal species in four dairy herds

The prevalence of staphylococcal species isolated from bovine mammary glands was determined in four dairy herds. Staphylococcus aureus and S hyicus were the predominant organisms isolated from cows in a herd with a bulk milk somatic cell count (SCC) greater than 900 X 10(3). One herd with a bulk milk SCC of 565 X 10(3) had a high incidence of S aureus while the predominant coagulase-negative species were S epidermidis and S hyicus. S hyicus predominated in two herds with bulk milk SCC less than 200 X 10(3); prevalence of S aureus was low. The impact of herd management practices such as post-milking teat antisepsis on distribution of staphylococcal species is discussed.     

Dynamics of Staphylococcus aureus infections during vaccination with an autogenous bacterin in dairy cattle

The effect of an autogenous vaccine against Staphylococcus aureus on S. aureus prevalence and mastitis, as well as on somatic cell count (SCC), was studied in a dairy herd with a high prevalence of S. aureus. The vaccination group (n = 35; 22 cows and 13 heifers) and the control group (n = 36; 23 cows and 13 heifers) received the vaccine or a placebo, respectively, according to the following protocol: all animals: basic immunization (twice, 3 weeks apart); cows: booster dose at the time of drying off, 5 and 2 weeks before calculated calving date; heifers: booster dose 2 and 5 weeks before calculated calving date. The vaccine or the placebo was administered subcutaneously in the area of the supramammary lymph nodes. Quarter milk samples were collected monthly and subjected to SCC and bacteriological evaluation. At this time, the animals were also checked for signs of clinical mastitis. Non-clinical S. aureus mastitis diagnoses were based on udder quarter SCC and a positive S. aureus culture. In order to compare the SCC in individual whole milk samples, records from the monthly milk quality testing were evaluated. Cow and udder quarter prevalence of S. aureus intramammary infections calculated for the experimental animals and quarters, respectively, did not differ between groups. However, during the lactation period following the boostcr dose, the prevalence of S. aureus increased in both groups (P < 0.05). The cumulative incidence of various mastitis diagnoses (clinical, subclinical, latent infection) due to S. aureus on an animal basis did not differ between groups. On an udder quarter basis, the cumulative incidence of subclinical mastitis was higher in vaccinated animals than in control animals (33.8 versus 26.0%; P < 0.05). This was mainly due to a higher cumulative incidence of subclinical mastitis in vaccinated than control heifers. The SCC in composite milk samples did not differ between groups, but increased as lactation progressed. The herd prevalence of S. aureus differed considerably throughout the study period, but declined consistently to below 10% at the end of the study period. Recent herd checks revealed a prevalence of S aureus infections of < 5%. It is concluded that the autogenous bacterin tested in this study did not have the desired effect on the prevalence of S. aureus infections and mastitis or SCC. The decline in S. aureus prevalence was very probably due to other factors than specific immunization against S. aureus.     

Controlling highly prevalent Staphylococcus aureus mastitis from the dairy farm

In 57 Holstein cows where the dairy farm uses a milking parlor system, the somatic cell count (SCC) increased persistently in the bulk milk (monthly mean 52.3 x 10(4) cells/ml; range 21 to 94 x 10(4) cells/ml). We detected S. aureus in 24 (41.2%) of the 54 lactating cows and in 29 (12.8%) of 227 quarters of the 57 milking cows in the herd. A control program was implemented in an effort to eradicate S. aureus mastitis from this dairy farm. The control plan established improved handling of the lactating cows, improved milking procedures, dry-cow therapy, and culling of infected cows. The program was monitored for 3.5 years by frequent checkups on the rate of S. aureus infection, the SCC, and the changes in milk composition. Eighteen months after the control program was started, the rate of S. aureus infection in the quarter milk decreased dramatically, and no S. aureus isolates were found in the milk of the remaining cows. The SCC in the bulk milk of the herd dropped to a monthly mean of <20 x 10(4) cells/ml. In conclusion, the control program was effective for controlling persistent S. aureus mastitis in this dairy herd.     

CNS mastitis: nothing to worry about?

In this paper, we analyzed a very large field data set on intramammary infections (IMI) and the associated somatic cell count (SCC) in dairy cows. The objective of the study was to analyze the impact of coagulase-negative staphylococci (CNS) IMI on cow SCC, both mean and variability, and on the potential of these infections to have a major impact on the bulk milk SCC (BMSCC). Data and milk samples for bacterial culture were collected by Quality Milk Production Services (QMPS) between 1992 and March of 2007. The QMPS program services dairy farms in New York State and other states in the Northeastern USA and operates in conjunction with Cornell University. Only records from cows where SCC and milk production data were available, and where only one organism was isolated from bacterial cultures of milk samples (or where culture was negative) were used for this analysis. A total of 352,614 records from 4200 whole herd mastitis screening sampling qualified for this study. Within herds an average of 15% (S.D. 12%) of cows sampled were infected with CNS, ranging between 0 and 100%. Average within herd prevalence of cows with a CNS IMI and an SCC over 200,000 cells/ml was 2% (S.D. 4%) with a minimum of 0% and a maximum of 50%. Results of linear mixed models showed three distinct populations of IMI statuses: negative cultures with the lowest SCC; CNS and Corynebacterium bovis with a moderate increase in SCC, and Streptococcus agalactiae, Streptococcus spp. and Staphylococcus aureus showing an important increase in SCC. Surprisingly, milk production was slightly but significantly higher in CNS infected cows compared to culture-negative cows, whereas it was strongly reduced in cows with a major pathogen IMI. The percentage contribution of CNS infections to the BMSCC was 17.9% in herds with a BMSCC less than 200,000 cells/ml. This value decreased to 11.9 and 7.9% in herds with bulk milk SCC between 200,000 and 400,000 and over 400,000 cells/ml, respectively. We concluded that very few herds with milk quality problems would have an important increase in BMSCC that could be mostly attributed to CNS infections. On the other hand, in herds with low BMSCC, CNS infections may be an important contributor to the total number of somatic cells in the bulk milk.     

Quarter milk somatic cell count in infected dairy cows: a meta-analysis

The aim of this paper was to evaluate the effects associated with intramammary infection (IMI) by a bacterium or a group of bacteria (Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, coliforms, Staphylococci other than S. aureus, and Corynebacterium bovis) on the somatic cell count (SCC) in quarter milk of dairy cows. Papers selected for analysis had to provide SCC values associated with the natural infection in quarters by different bacteria. Sampling for measurement of SCC and determination of the infection had to be done on the same day. Only papers published in English or in French after 1971 were considered. Twenty-one papers fulfilled the selection criteria. The animals sampled, the measurement techniques for SCC and the bacteriological identification, as well as the definition of the infection, all differed widely among the selected studies. The meta-analysis method was used to estimate both the mean SCC (arithmetic and geometric) value and the average increase on SCC of each type of infection. The geometric mean SCC in bacteriologically negative quarters was 68 000 c/mL. In case of IMI, the retained SCC was 357 000, 857 000, 547 000, 1 024 000, 1 151 000, 138 000 and 105 000 c/mL in quarters infected by Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, coliforms, staphylococci other than S. aureus and Corynebacterium bovis, respectively. The variation factors that could influence these SCC values and the bacteriological results are discussed.     

Somatic cell count in milk of selenium-supplemented dairy cows after an intramammary challenge with Staphylococcus aureus

The objective of this study was to evaluate the effect of selenium (Se) supplementation on milk somatic cell count (SCC) in dairy cows. Twelve multiparous Holstein-Friesian cows were fed a diet containing a suboptimal Se concentration (<0.05 ppm, dry basis) starting 2 months before calving. Supplemented cows (n=6) received a single s.c. injection of barium selenate (1 ml/50 kg BW) 45 days prior to calving, whereas control group was kept unsupplemented. Twenty weeks after calving, two mammary quarters (right side) of each cow were challenged with 205,000 cfu/ml of Staphylococcus aureus (strain Newbould 305). Blood was collected bi-weekly until day 150 of lactation for the analysis of blood glutathione peroxidase (GPx1; EC 1.11.1.9) activity. To re-isolate the challenging pathogen and to evaluate SCC, aseptic milk samples were collected daily starting on the day of challenge, and finishing 7 days after inoculation. Unsupplemented cows had a lower activity of GPx1 through the experiment (P<0.001). Natural log SCC (lnSCC) was higher in unsupplemented than Se-supplemented cows (P=0.04), showing evidence of significance after 5 days. Selenium supplementation of dairy cows fed a diet containing a suboptimal Se concentration, resulted in higher blood activity of GPx1, and lower mean lnSCC after an intramammary challenge with Staph. aureus.     

Effect of intramammary injection of RbIL-8 on milk levels of somatic cell count, chemiluminescence activity and shedding patterns of total bacteria and S. aureus in Holstein cows with naturally infected-subclinical mastitis

Summary The effect of intramammary injection of recombinant bovine interleukin-8 (rbIL-8, 1 mg/10 ml of saline) on quarter milk levels of somatic cell count (SCC), chemiluminescence (CL) activity and counts of total bacteria and Staphylococcus aureus (S. aureus) was investigated, using 10 Holstein cows with an early stage or a late stage of subclinical mastitis naturally infected with S. aureus. In the late-stage group, milk SCC and CL activity had significant rises with maximum levels at 6 h, following maintained high levels thereafter post-cytokine injection. The counts in milk total bacteria and S. aureus were insignificantly decreased, being increased back on day 7 post-cytokine injection. Thus, the cytokine was inefficient for the late-stage subclinical mastitis. However, in the early-stage group milk SCC and CL activity declined to under pre-injection levels on day 7 after marked and significant rises at 6 h and day 1 post-cytokine injection. The milk total bacterial count decreased significantly on days 0.25 and 2. Furthermore, the milk S. aureus count was decreased significantly on days 1, 2, 3 and 7 by the cytokine injection. These results suggest that the rbIL-8 has a potential as a therapeutic agent of the subclinical mastitis of dairy cows, if the cytokine is applied at an initial stage of infection.     

Prevalence and herd-level risk factors for intramammary infection with coagulase-negative staphylococci in Dutch dairy herds

In this study, the prevalence of intramammary infection (IMI) with coagulase-negative staphylococci (CNS) in The Netherlands was estimated on 49 randomly selected herds with at least 40 lactating cows. In total, 4220 quarter milk samples were collected. The prevalence of CNS IMI in The Netherlands was estimated at 10.8% at quarter level and 34.4% at cow level, making it the most frequently isolated group of pathogens. Fourteen species of CNS were identified; the most frequently isolated species was Staphylococcus chromogenes (30.3%) followed by Staphylococcus epidermidis (12.9%) and Staphylococcus capitis (11.0%). Prevalence of CNS IMI was higher in heifers compared to older cows. Geometric mean quarter SCC of CNS-positive quarters was 109,000 cells/ml, which was approximately twice as high as culture-negative quarters. Quarters infected with S. chromogenes, S. capitis and Staphylococcus xylosus had a higher SCC (P<0.05) than culture-negative quarters, while quarters that were culture-positive for S. epidermidis and Staphylococcus hyicus tended to have a higher SCC than culture-negative quarters. An increased prevalence of CNS IMI was associated with the herd-level variables source of drinking water not being tap water, housing of dry cows in one group instead of multiple groups, measurement of cow SCC every month, udder health monitoring by the veterinarian, pasturing during outdoor season, percentage of stalls contaminated with milk, and BMSCC>250,000 cells/ml. Although a causal relation between these factors and prevalence of CNS is not proven and for some factors not even likely, knowledge of the associations found may be helpful when approaching CNS problems on dairy farms.     

Effect of intramammary injection of rboGM-CSF on milk levels of chemiluminescence activity, somatic cell count, and Staphylococcus aureus count in Holstein cows with S. aureus subclinical mastitis

The effect of intramammary injection of recombinant bovine granulocyte-macrophage colony-stimulating factor (rboGM-CSF, 400 microg/10 mL) on quarter milk levels of chemiluminescence (CL) activity, and somatic cell count (SCC) and shedding pattern of Staphylococcus aureus was investigated. Ten Holstein cows, naturally infected with S. aureus were used, with either early-stage or late-stage subclinical mastitis. Injection of rboGM-CSF caused a remarkable increase in milk CL activity with a peak at 6 h after the cytokine injection in the early- and late-stage groups. In the early-stage group, milk SCC stayed around preinjection level at 6 h, rose significantly on days 1 and 2, and was followed by a smooth and significant decline to an under preinjection level (below 200 000 cells/mL) on day 7 postinjection. Alternatively, in the late-stage group, milk SCC rose significantly at 6 h after the cytokine injection and maintained high levels thereafter. The milk S. aureus count decreased drastically by the cytokine injection in the early-stage group. The bacterial count was moderately decreased in the late-stage group, but increased back to preinoculation levels on day 7 after the cytokine injection. The results suggest that the rboGM-CSF has a potential as a therapeutic agent for S. aureus infection causing subclinical mastitis of dairy cows, if the cytokine is applied at the initial stage of infection.     

复合植物提取物对奶牛产奶量、乳成分和血液指标的影响

本试验旨在研究日粮中添加复合植物提取物对奶牛产奶量、乳成分和血液生理生化指标的影响。选择25～27月龄、1胎、泌乳天数(67±1) d、产奶量(32±5) kg/d且健康的泌乳高峰期荷斯坦奶牛40头,随机分为对照组和试验组,每组20个重复,每个重复1头牛。对照组饲喂基础日粮,试验组饲喂基础日粮+1g/(d·头)复合植物提取物(每克含辣椒油树脂3.5%、肉桂醛5.5%、丁香酚9.5%)。试验预试期3d,正试期60 d。结果表明:与对照组相比,试验组奶牛产奶量提高2.37%(P>0.05);日粮添加复合植物提取物有降低牛奶体细胞数、尿素氮含量的趋势(P>0.05);与对照组相比,试验组奶牛血常规指标、血清生理生化指标差异均不显著(P>0.05)。在本试验条件下,日粮添加1 g/(d·头)复合植物提取物能够在一定程度上提高奶牛产奶量、降低牛奶体细胞数和尿素氮含量,但不影响血液生理状态。     

Prevalence and persistence of coagulase-negative Staphylococcus species in three dairy research herds

Coagulase-negative Staphylococcus species (CNS) were isolated from 11.3% (1407 of 12,412) of mammary quarter milk samples obtained from cows in three dairy research herds in 2005. Approximately 27% (383/1407) of CNS was identified to the species level. The species distribution among those CNS identified from all herds was Staphylococcus chromogenes (48%), Staphylococcus hyicus (26%), Staphylococcus epidermidis (10%), Staphylococcus simulans (7%), Staphylococcus warneri (2%), Staphylococcus hominis (2%), Staphylococcus saprophyticus (1%), Staphylococcus xylosus (1%), Staphylococcus haemolyticus (<1%), Staphylococcus sciuri (<1%), and Staphylococcus intermedius (<1%). Staphylococcuschromogenes was the predominant CNS isolated from all three herds; however, differences were seen in the prevalence of other CNS species. A total of 158 CNS (S. chromogenesn=66, S. hyicusn=38, S. epidermidisn=37, S. simulans n=10, and S. warneri n=7) were analyzed by pulsed-field gel electrophoresis (PFGE). The majority (33/41) of CNS isolated from the same mammary quarter on more than one occasion had the same PFGE pattern indicating persistence of the same infection over time. When all PFGE patterns for each CNS were analyzed, no common pulsotype was seen among the three herds indicating that CNS are quite diverse. Composite milk somatic cell count (SCC) data were obtained +/-14d of when CNS were isolated. Average milk SCC (5.32 log(10)/ml) for cows in which CNS was the only bacteria isolated was significantly higher than the average milk SCC (4.90 log(10)/ml) from cows with quarter milk samples that were bacteriologically negative.     

基于DHI平台开展奶牛乳房炎诊断及治疗效果的研究

为评估DHI中的体细胞值对奶牛乳房炎的预警作用,以湖南省DHI中心对宁乡某规模化奶牛场2019年3-4月份DHI数据为基础,结合乳房炎快速检测液,筛选临床或隐性乳房炎奶牛,确定为药物治疗效果试验组。采集筛选牛群奶样,进行细菌分离培养、鉴定,结合药敏实验开展针对性治疗,观察治疗效果。结果发现:从试验组奶样中均分离出各种乳房炎致病菌,其中主要是大肠杆菌和金黄色葡萄球菌;经敏感药物治疗后,患牛乳中体细胞数(SCC)下降极显著(P<0.01)。结论:体细胞数(SCC)作为DHI检测的一项重要指标,对奶牛乳房炎起到第一预警作用;DHI报告同时针对出现的问题提出相应的改进措施,以期使DHI成为牛场发现管理问题、增加养殖效益的有效工具,切实服务于奶牛场的实际生产。     

Phagocytic and bactericidal activity of blood and milk-resident neutrophils against Staphylococcus aureus in primiparous and multiparous cows during early lactation

To examine the effect of parity on polymorphonuclear neutrophils (PMN) function, phagocytic and bactericidal activity of the PMN isolated from blood and milk against Staphylococcus aureus was compared between groups of 6 primiparous and 6 multiparous healthy dairy cows during early lactation using bacteriological and PMN-pathogen interaction assays. Latex-stimulated luminol-amplified chemiluminescence (CL) and viability of these PMN were also investigated. The phagocytosis and killing of S. aureus by blood were remarkably higher than those of milk PMN. Similarly, the CL and viability in blood PMN were markedly higher than in milk PMN. Both in blood and in milk the phagocytosis of S. aureus by PMN in primiparous cows was substantially higher than in multiparous cows. The killing activity of blood PMN against S. aureus was 42.3+/-3.4% and 23.2+/-1.7% in primiparous and multiparous, respectively. Milk PMN killed only 20.7+/-2% S. aureus in primiparous and 10.2+/-1.3% in multiparous cows. Blood and milk PMN CL and milk PMN viability were significantly higher in primiparous cows. The pronounced reduction in phagocytic and bactericidal activity in blood and milk-resident PMN from multiparous cows, in part, resulted from the pronounced decrease of PMN viability and free radicals production capacity; this suggests that heifers' udders could be more protected against S. aureus, which remains to be tested in the field.     

Etiology and antimicrobial susceptibility of udder pathogens from cases of subclinical mastitis in dairy cows in Sweden

Background

A nationwide survey on the microbial etiology of cases of subclinical mastitis in dairy cows was carried out on dairy farms in Sweden. The aim was to investigate the microbial panorama and the occurrence of antimicrobial resistance. Moreover, differences between newly infected cows and chronically infected cows were investigated.

Methods

In total, 583 quarter milk samples were collected from 583 dairy cows at 226 dairy farms from February 2008 to February 2009. The quarter milk samples were bacteriological investigated and scored using the California Mastitis Test. Staphylococci were tested for betalactamase production and presence of resistance was evaluated in all specific udder pathogens. Differences between newly infected cows and chronically infected cows were statistically investigated using logistic regression analysis.

Results

The most common isolates of 590 bacteriological diagnoses were Staphylococcus (S) aureus (19%) and coagulase-negative staphylococci (CNS; 16%) followed by Streptococcus (Str) dysgalactiae (9%), Str. uberis (8%), Escherichia (E.) coli (2.9%), and Streptococcus spp. (1.9%). Samples with no growth or contamination constituted 22% and 18% of the diagnoses, respectively. The distribution of the most commonly isolated bacteria considering only bacteriological positive samples were: S. aureus - 31%, CNS - 27%, Str. dysgalactiae - 15%, Str. uberis - 14%, E. coli - 4.8%, and Streptococcus spp. - 3.1%. There was an increased risk of finding S. aureus, Str. uberis or Str. dysgalactiae in milk samples from chronically infected cows compared to findings in milk samples from newly infected cows. Four percent of the S. aureus isolates and 35% of the CNS isolates were resistant to penicillin G. Overall, resistance to other antimicrobials than penicillin G was uncommon.

Conclusions

Staphylococcus aureus and CNS were the most frequently isolated pathogens and resistance to antimicrobials was rare.     

Development of a Staphylococcus aureus vaccine against mastitis in dairy cows. II. Field trial

A recently described new Staphylococcus aureus vaccine "MASTIVAC I" (Patent no. PTC/IL98/00627) against S. aureus udder infection elicited protection against experimentally induced infection in cows. In the present paper we describe a large-scale vaccination field trial. A total of 452 Israeli Holstein heifers were included in the study over two consecutive years. Approximately half of the heifers (228) were vaccinated while the others (224) served as a control group. Antibody response was detected in all vaccinated animals 4-5 weeks post-primary immunization and it was sustained throughout the experimental period (300-330 days). S. aureus infection could be detected in only 3 out of 228 animals (1.3%) in the vaccinated group and in 6 out of 224 (2.7%) in the control group. These numbers were too low to be statistically evaluated. However, when somatic cell counts (SCC) and milk yields were considered, a significant difference was found between the two groups, namely, the vaccinated cows in first and second lactation had 42 and 54%, respectively, lower SCCs and milk yields 0.5 kg per day higher than the non-vaccinated control cows. These results suggest that the new vaccine elicits a non-specific health improvement of the udder in addition to specific protection against S. aureus.     

利福昔明乳房注入剂(干乳期)对奶牛的安全性研究

研究利福昔明乳房注入剂(干乳期)对健康奶牛的正常体温、日产奶量、奶中体细胞数和乳房内菌群的影响。选择健康泌乳期奶牛12头,给药前1 d和给药前0 d,统计记录各试验奶牛的直肠温度、日产奶量,检测每个乳区采集奶样的体细胞数,并对给药前0 d的奶样进行病原菌分离检测。每头入选奶牛的四个乳区分别单次灌注利福昔明乳房注入剂,在给药后的第1、3、5、7、10天分别记录每头奶牛的日产奶量;在给药后的第12小时、3、5、7、10天分别采集奶样进行体细胞检测,同时检查直肠温度;在给药后的第10天对采集的奶样进行病原菌检测。比较奶牛用药前后直肠温度、日产奶量、奶中体细胞数和病原菌的变化。试验期间对给药奶牛进行连续观察,记录奶牛是否出现红、肿、热、痛等临床症状。结果表明。给药前1 d、给药当天和最后一次给药后的第1、3、5、7、10天,试验奶牛的日产奶量平均值分别为30.5、30.3、29.8、30.3、30.0、30.9和31.0 kg,相互之间无显著性差异(P>0.05);给药前后各时间点采集的奶中体细胞数大都维持在30~50万/mL;给药前后各时间点测得的奶牛直肠温度无显著性差异(P>0.05);病原菌检测结果显示,在给药前0 d分离到7株大肠杆菌、6株链球菌和9株葡萄球菌,给药后第10天采集的奶样中未检测到大肠杆菌和葡萄球菌,仅检测到1株链球菌。与给药前相比,奶中的病原菌数量有所减少,无新增感染。利福昔明乳房注入剂(干乳期)对奶牛正常体温、产奶量、奶中体细胞数无不良影响,该制剂对于奶牛是安全的。     

Prevalence study of Staphylococcus aureus in quarter milk samples of dairy cows in the Canton of Bern, Switzerland

In the present study, the prevalence of S. aureus in mammary gland quarters of dairy cows in Switzerland was estimated and a risk factor analysis was carried out. Dairy cows were selected by one-step-cluster sampling with stratification by herd size. Forty-seven of 50 randomly chosen farms participated in the study, resulting in 603 cows and 2388 quarter samples. Milk samples were collected in all herds on two occasions two weeks apart. In 6% of cows (95% CI: 2.7-9.3%) at least one milk sample was positive for S. aureus and from 2% (0.8-3.2%) of all quarters, S. aureus was cultured at least once. In four quarters a latent S. aureus infection (agent detected and somatic cell count (SCC) <100,000cell/ml) was diagnosed. Multivariable hierarchic logistical regression analysis yielded five significant risk factors for observing S. aureus in a milk sample: high SCC, a S. aureus-positive neighbouring quarter, a palpable induration in the quarter, and a wound, scar tissue or crush injury affecting the teat. The type of housing (P=0.1596) was also a factor that remained in the model. The mentioned risk factors must be considered during the evaluation of herds with S. aureus problems. The occurrence of latent S. aureus infections emphasises that not only quarters with a high SCC but all quarters of all cows must be cultured for control measures to be effective.     

Intramammary treatment of clinical mastitis of dairy cows with a combination of lincomycin and neomycin, or penicillin and dihydrostreptomycin

AIM: To compare clinical and bacteriological cure rates of clinical mastitis following treatment with intramammary preparations containing either lincomycin and neomycin or penicillin and dihydrostreptomycin. METHODS: Cases of clinical mastitis were sourced from four seasonal-calving dairy herds in the central Waikato region of New Zealand during the first 120 days of lactation. Affected quarters were infused three times at 12 h intervals with either 333 mg lincomycin plus 100 mg neomycin (lin/neo; 197 glands),or 1,000 mg penicillin plus 500 mg dihydrostreptomycin (pen/DHS; 207 glands). Milk samples were collected for bacteriology from each quarter immediately before and approximately 21 days after initiation of treatment. Additionally, a composite milk sample from each cow was collected, on average, 54 days after enrolment for assessment of milk yield, composition and somatic cell count (SCC). The probability of bacterial cure was initially analysed using Chi-squared analysis, and factors that were associated (p<0.2) were offered to a reverse stepwise logistic regression model. Continuous variables (e.g. milk solids production and log10 SCC) were analysed using general linear models. RESULTS: A total of 404 quarters diagnosed with clinical mastitis, from 282 cows in the first 120 days of lactation, were included. Streptococcus uberis, coagulase-negative staphylococci and Staphylococcus aureus were isolated from 56.5%, 18.8% and 10.0% of the bacteriologically positive quarters. There was no difference in the bacteriological cure rate (76.7% vs 76.7%, OR=0.94; p>0.8), the log10 SCC (2.1, SE 0.1, vs 2.0, SE 0.1; p>0.3) or milk production (1.2, SE 0.1, vs 1.2, SE 0.1, kg milksolids/cow/day; p>0.7) between lin/neo vs pen/DHS treatments, respectively. However, the proportion of cows re-treated following initial treatment was higher for the lin/neo compared to pen/DHS-treated group (16.3% vs 5.2%, OR=3.46; p<0.05). CONCLUSIONS: No difference in bacteriological cure rate, milk production or SCC was evident between lin/neo and pen/DHS intramammary treatments for clinical mastitis in dairy cows during the first 120 days of lactation. KEYWORDS: Dairy cow, mastitis, intramammary, antibiotic, treatment, somatic cell count.