Risk Factors For Subclinical Mastitis Research Articles

Seasonal, physiological and bacteriological risk factors for subclinical mastitis in dairy cows maintained under different farming conditions.

Subclinical mastitis (SCM) is a major health problem of dairy animals in India and across the globe. An identification of potential risk factors of SCM can help for efficient udder health management in dairy animals. In this study, apparently healthy cows (HF crossbred: n = 45; Deoni: n = 43) were screened for SCM during different seasons through milk somatic cell count (SCC: reference test using 200 × 103 cells/ml as cut off value), California mastitis test (CMT) and differential electrical conductivity (DEC) test at an organized research farm. SCM positive milk samples (n = 34) were inoculated in selective media for Coliform sp., Streptococcus sp. and Staphylococcus sp. and DNA was isolated (n = 10) for species confirmation by 16s rRNA method. Both bivariate and multivariate models were used for risk assessment. We found the cumulative prevalence of 31 and 65% SCM in Deoni and crossbred cows, respectively. Screening of 328 crossbred cows under field conditions revealed point prevalence of 55% SCM. Multivariate analysis revealed stage of lactation (SOL), milk yield in previous lactation and test day milk yield in Deoni cows, as well as parity and mastitis treatment history in current lactation in HF crossbred cows as risk factors. SOL was a significant factor under field conditions. Receiver operated characteristic curve analysis revealed better accuracy of CMT than DEC. We found more mixed infections due to Staphylococcus sp. and Streptococcus sp. in culture, while 16s rRNA based molecular method revealed lesser-known pathogens associated with SCM. It is concluded that SCM prevalence rate is higher in crossbred than indigenous cows and these breeds have different risk factors for SCM. HF crossbred cows had similar SCM prevalence rate under different farming conditions, where CMT can be used for SCM diagnosis with excellent accuracy. The 16s rRNA method is useful for specific identification of lesser known and emerging mastitis pathogens.

Subclinical mastitis in dairy cows in south-Asian countries: a review of risk factors and etiology to prioritize control measures.

Mastitis is a major production disease, causing significant economic losses for dairy farmers in South-Asian countries, as well as other parts of the world. Udder health control programs (UHCP) have been established in developed countries as an effective strategy for mastitis control but have not yet been introduced in South-Asian low-income countries like Bangladesh, India, Pakistan, and Sri Lanka. To launch UHCP successfully in dairy herds in South-Asia, it is important to know the current prevalence and risk factors for subclinical mastitis (SCM). Therefore, a narrative literature review was conducted with the aim to describe the dairy sector, the prevalence of SCM and its causal agents, risk factors for mastitis occurrence and the control measures suggested by different studies conducted in the selected countries. The literature revealed that India had the highest cattle population. Milking was mainly done by hand in all of the studied countries. Stall feeding was done in Bangladesh and Sri Lanka and limited access to grazing was also reported in some farms in India and Pakistan. There was substantial variation in the prevalence of SCM between studies in all 4 countries, ranging from about 20% to about 80%, but the average prevalence across all studies was high (50%). The most common causal agents for SCM were non-aureus staphylococci (NAS), Staphylococcus (S.) aureus, Streptococcus spp. and Escherichia (E.) coli. The management related risk factors reported for SCM were stall feeding of cows, a higher stock density, cracked floors, open drains, the presence of flies, poor drainage, peri-parturient diseases, infrequent dung removal and earth floors. The control measures suggested in these studies were to improve the hygiene and sanitation of cows, to improve the cleanliness of farms and milker's hands, to apply dry cow therapy, supplementing micronutrients and routine screening for SCM combined with taking intervention measures like isolation of cows or milking infected cows last, and proper treatment. Also, full hand milking, complete milking, machine milking, and providing feed and water immediately after milking have been recommended. Finally, we show that current literature often studies the same set of (non-manageable) risk factors, so more research is needed to obtain a comprehensive picture of the determinants of SCM. Randomized controlled trials are needed to truly quantify the effect of intervention under field conditions. Altogether, our work gives an overview of the udder health situation in South-Asia and provides the basis for the design of UHCP in this region.

Risk factors for intramammary infection in meat- and pelt producing ewes with clinically healthy udders

Mastitis is prevalent both in milk- and meat- and pelt producing sheep flocks and is an important disease with substantial effects on economy, animal welfare and antibiotic use, and in dairy flocks also on milk quality and safety. In meat- and pelt producing flocks, the farmers are mainly concerned by clinical mastitis (CM), and most cases of subclinical mastitis (SCM) are not detected and not dealt with, posing a risk for poor udder health in the flock. Studies on risk factors for SCM and/or intramammary infections (IMI) in meat producing flocks are scarce and specific risk factors for weaning and lambing are absent. The aim of this study was therefore to investigate associations between risk factors, at ewe and flock level, for IMI after lambing and at weaning in Swedish meat- and pelt producing ewes with clinically healthy udders. Twenty-two meat- and pelt producing flocks from different parts of Sweden were enrolled in this cross-sectional study. Udder half milk samples were collected at weaning and after lambing from ewes with clinically healthy udders, for bacteriological investigations. Data on ewe and flock level risk factors were recorded. In total, 753 ewes were sampled at least once, and the overall IMI prevalence was 22.5 %. Older ewes, ewes with three or more lambs, ewes that were hard to milk when collecting a milk sample, ewes in moderate size flocks, in flocks with hay as a bedding material and in flocks with less cases of CM had higher risk of IMI. Most of the risk factors associated with IMI in this study differed between weaning and lambing. This study has provided us with novel knowledge on how different factors influence udder health of meat- and pelt producing ewes.

Molecular detection, antibiogram, and risk factor analysis of Staphylococcus aureus from subclinical mastitis of goats in conventional and organized farms

Objectives: The goal of this study was to isolate, molecularly identify, and antibiogram of Staphylococcus aureus, as well as to investigate risk factors for subclinical mastitis in the Jhenaidah and Chuadanga districts of Bangladesh. Materials and Methods: A total of 100 milk samples were collected from apparently healthy goats at various farms in the Jhenaidah and Chuadanga districts. To detect samples with subclinical mastitis (SCM), the California Mastitis Test (CMT) was done. S. aureus was isolated and identified from milk samples that tested positive for CMT using a combination of standard bacteriological examinations, biochemical tests, and PCR confirmation. The disc diffusion test was used to determine the antibiogram status of the isolates. The risk factors for SCM in goats were analyzed using a semi-structured questionnaire with thirteen variables. Results: Some characteristics were significantly associated with goat mastitis, including farm, breed, shed construction, floor surface condition, and farm adviser. The CMT identified 52 positive samples for SCM, with 73.07% (n = 38/52) suggesting the presence of the nuc gene. Antibiotic susceptibility testing revealed that the isolated S. aureus was totally resistant to the antibiotics Penicillin, Oxacillin, and Vancomycin (21%). On the other hand, Tetracycline, Gentamycin, Norfloxacin, and Levofloxacin were all susceptible to all isolates. Conclusion: SCM is a severe problem in goats in Jhenaidah and Chuadanga districts. To minimize the risk of SCM infection in goats, hygiene precautions can be followed, and education among goat farm owners and farmers can be improved.

Prevalence of sub-clinical mastitis and its association with milking practices in an intensive dairy production region of Uganda.

A cross-sectional study was conducted to investigate the risk factors for sub-clinical mastitis (SCM) in Mbarara District, an intensive dairy production region of Uganda where hand-milking is dominant. In 30 farms, herd-level milking practices and SCM prevalence were studied. The SCM prevalences were 68.6% (417/608, 95% confidence interval (CI): 64.9–72.2%) and 39.2% (946/2,411, 37.3–41.2%) at the cow- and quarter-levels, respectively. A preventive factor for SCM was cow calmness at the end of milking (OR: 0.20, 95%CI: 0.05–0.79, P=0.021); a risk factor was rough teat-end (OR: 1.75, 95%CI: 1.14–2.68, P=0.011). Good cow hygiene was negatively associated with environmental mastitis (P=0.002). Appropriate hand-milking practices that avoid teat damage are expected to reduce SCM in Uganda.

Epidemiology of Sub-Clinical Mastitis in Dairy Cows in Urban Areas of Chittagong, Bangladesh

Mastitis is considered to be the most devastating condition for the dairy farms of low and medium income countries due to its alarming impact on production and worldwide has been recognized as one of the most economically significant infectious diseases affecting the welfare of dairy animal. Chittagong is one of the dairy intensive regions of Bangladesh but comprehensive epidemiological studies addressing prevalence of and risk factors for subclinical mastitis (SCM) are scant. Therefore we aimed to approximate the prevalence of SCM in dairy cows along with the associated risk factors in dairy cows of Chittagong Metropolitan Area (CMA), Bangladesh. We included 114 cross breed (Holstein × Local) lactating cows, raised at 6 dairy farms in CMA between February to November, 2015 for this study. California Mastitis Test (CMT) was used to assess SCM at animal level. The overall prevalence of mastitis was 34.2% among the tested cows. Floor type, source of replacement cows, history of previous reproductive disorder, stage of lactation and cleanliness of floor was found significantly associated with SCM in univariate analysis. In random effect multiple logistic regression model, cemented floor was found to increase the odds of SCM by 5.03 times than that of brick floor. Similarly, cows with history of reproductive disorders had more risk of having SCM than that of cows without a history of reproductive disorders. Since the SCM is prevalent in the study area, the intervention strategy should focus on causal agent, improved management, frequent monitoring of SCM in milking cows with CMT and use of teat disinfectants; with minimal or no treatment with antimicrobial agents.

English

The microbial diversity of a pooled milk sample (H) from healthy dairy cows in the Daqing region of Heilongjing Province in northeastern China was compared to that of four pooled milk samples (M1-M4) from dairy cows from the same area previously diagnosed with subclinical mastitis, based on the California mastitis test, using pyrosequencing of the metagenomic 16S ribosomal RNA genes. A total of 22 759 valid sequences were obtained from the five pooled milk samples, and the average length of a valid sequence was 484 bp. The composition of the bacterial communities of the M1, M2, M3, and M4 samples was significantly different from that of the H sample. The bacterial diversity of the M1 sample was highly similar to that of M2 sample; the bacterial diversity of the M3 sample was highly similar to that of M4 sample. The Streptococcus and Staphylococcus spp. were highly prevalent in the M1, M2, and M4 samples, and Pseudomonas spp. were highly prevalent in the M1, M2, and M3 samples. The levels of Acinetobacter, Lactococcus, and Flavobacteriaceae spp. in the M1, M2, M3, and M4 samples were lower than those of the H sample, which represents potential risk factors for subclinical mastitis. Our findings provide valuable information relevant to the prevention and treatment of subclinical mastitis in dairy cows in northeastern China. Key words: subclinical mastitis, microbial diversity, pyrosequencing.

Expert opinion on ranking risk factors for subclinical mastitis using a modified Delphi technique

AIM: To collate the expert opinion of Australian dairy practitioners on the relative importance of risk factors for subclinical mastitis in dairy cattle. METHODS: A modified Delphi technique was used to collect the data over two rounds. First, participants were asked to complete a survey involving ranking the level of importance of 42 risk factors on the incidence of subclinical mastitis on a scale from 1 to 10 for two categories of subclinical mastitis; contagious and environmental. After presenting and discussing the results of the first survey, the participants were asked to complete the same survey a second time. To rank the risk factors and identify the consensus amongst the participants, the median and total variation of answers were calculated and compared between the two surveys. RESULTS: The most important factors identified by the respondents after the second survey for contagious subclinical mastitis were: Teat Disinfection Post-milking, Management of High Cell Count Cows and Presence of Chronically Infected Mastitis Cows in the Herd. The most important factors for environmental subclinical mastitis were Cleanliness of the Environment and Technique of Teat Disinfection Post-milking. CONCLUSIONS: A movement toward consensus for the more important factors and a movement away from consensus for the less important factors in the second survey were observed. The most important factors for subclinical mastitis were found to be: teat disinfection post-milking, management of high cell count cows, presence of chronically infected mastitis cows in the herd and cleanliness of the environment.

Prevalence and risk factors of subclinical mastitis in lactating dairy cows in north and south regions of Bangladesh

The purpose of the study was to identify the potential risk factors for subclinical mastitis (SCM) in lactating dairy cows in Bangladesh. A cross-sectional study was carried out on randomly selected 212 smallholder dairy farms of Sadar upazilas of Rangpur, Mymensingh, and Satkhira districts of Bangladesh during January to October 2011. The direct interview using a structured questionnaire and physical examination of the cows were done to collect data on 15 variables. Milk samples collected from study cows were subjected to California Mastitis Test (CMT). The diagnosis of SCM was based on the results of CMT and physical examination of udder and milk. The bivariable followed by multivariable analysis was done using SPSS 17.0. Of the total cows examined, 20.2 % had subclinical mastitis. In bivariable analysis, eight risk factors were identified. However, in the final model of multivariable analysis, four potential risk factors were identified. These were history of previous clinical mastitis (odds ratio (OR) 10.51, p<0.001), pendulous type of udder (OR 2.26, p=0.008), no grass feeding (OR 1.84, p=0.039), and body condition score (BCS) 2.5 or less (OR 7.25, p=0.054). Four different factors were significantly associated with the occurrence of subclinical mastitis, which need to be considered in the control of the disease. However, particular emphasis should be given on grass feeding and BCS because these traits can be modified or improved to allow prevention of SCM.

Risk factors associated with buffalo mastitis in the Brazilian Northeast

Risk factors for subclinical mastitis were studied in 474 buffaloes cows proceeding from four dairy farms located in the states of Pernambuco, Alagoas, Bahia and Ceará, Brazil. Milk samples (n=1896) of lactating buffaloes cows were examined for somatic cells count (SCC) and microbiologic exam, and a questionnaire composed by objective questions was applied in order to obtain animals and herd management data. Risk factors analysis was performed in two stages: univariate and mutivariate analysis. Two analysis were performed, one considering the animal classification for SCC as the dependent variable (&lt;400,000 - negative; &gt;400,000 - positive) and another, considering the microbiologic exam result (positive and negative). In the multivariate analysis considering SCC as dependent variable, the lack of teat washing was the only variable identified as a risk factor, so that farms without this procedure before the milking presented risk of infection of 2.68 (I.C. 1.49-4.83). In the multivariate analysis considering the microbiologic exam as dependent variable, it was observed that properties that performed the cleaning of the milking equipment manually presented risk of 1.85 (I.CI. 1.32-3.64), which was higher than those properties that performed the cleaning mechanically (p=0.019). Risk factors for the occurrence of subclinical mastitis in dairy buffaloes in Brazilian Northeast farms were related to the characteristics of improper milking management. Risk factors identified in this study must be carefully corrected in order to reduce the frequency of mastitis cases, and therefore, contribute for disease control and prevention in the herds.

In this issue – January/February 2011

The life of veterinarian Ernest Arthur Kendall · Sequential opportunistic infections in German Shepherd dogs · Small intestinal ganglioneuromatosis in a dog · Options for preventing flystrike in Merino lambs · Wound healing after mulesing and other options · Vaccination and ovine Johne's disease · Risk factors for subclinical mastitis on dairy farms · Parasites in tawny frogmouths · Peritoneopericardial diaphragmatic hernia in an alpaca · Gammaherpesvirus infection in a kangaroo

Prevalence, incidence and risk factors of heifer mastitis

Traditionally heifers, as calves and as primiparae, have been thought of as a group as free of mastitis. Without appreciable lacteal secretion, there is reduced nutrient fluid available to support growth of intramammary pathogens. Contagious mastitis is primarily transmitted at milking time and the milking process affects the patency of the teat orifice which can increase the risk of development of environmental mastitis. Logically therefore prepartum heifers should be free of intramammary infections. During the last 20 years there have been numerous investigations describing the nature of mastitis in heifers and thus the dogma that heifers are free of this disease has been challenged. The purpose of this manuscript is to review that literature describing heifer intramammary infections that cause both subclinical and clinical disease. Mammary quarter infection prevalence ranges between 28.9–74.6% prepartum, and 12.3–45.5% at parturition. Generally, the pathogens that cause mastitis in heifers are the same as those that cause infections in the older cows. In all but one study reviewed, coagulase-negative staphylococci (CNS) are the most prevalent cause of subclinical intramammary infections in heifers. Coagulase-positive staphylococci (CPS) in some studies are the second most prevalent pathogens, while in other studies the environmental mastitis pathogens are more prevalent. The risk factors for subclinical mastitis appear to be season, herd location, and trimester of pregnancy; all suggesting that management can have an impact in control of this disease prepartum. With respect to clinical mastitis, the most prevalent mastitis pathogen has been reported to be CNS in one study and CPS, or environmental mastitis pathogens, in other studies. The heifer is most at risk for clinical mastitis during the periparturient period. Risk factors found are related to diet, mammary gland factors such as edema and leaking of milk, and factors associated with the change in management and introduction of the heifer to the milking herd.

Prevalence of subclinical mastitis and associated risk factors in smallholder dairy cows in Tanzania

A cross-sectional study was carried out on 200 randomly selected farms in each of the Iringa and Tanga regions of Tanzania to estimate the prevalence and risk factors for subclinical...

Fatores de risco para mastite subclínica em vacas leiteiras

Os fatores de risco para mastite subclínica (CCS &gt; 200.000 células/ml) foram estudados em 2.657 vacas, de 24 rebanhos de Minas Gerais. Cada rebanho foi visitado três vezes entre novembro de 2005 e junho de 2006. Amostras de leite (n=3.987) de vacas em lactação foram examinadas para contagem de células somáticas (CCS), e um questionário foi aplicado para obtenção de dados dos animais e do manejo do rebanho. Os valores para a média, mediana e desvio-padrão da CCS foram 608.000, 219.000 e 967.000 células/ml, respectivamente. Os fatores de risco para mastite subclínica foram: animais com a base do úbere junto ou abaixo do jarrete, rachaduras ou fissuras nas partes de borracha do equipamento de ordenha, inadequação das teteiras, deficiência de limpeza dos pulsadores, falta de treinamento dos ordenhadores, não-utilização de diagnóstico microbiológico para mastite, imersão do conjunto de teteiras em solução desinfetante entre a ordenha de animais distintos, e inserção total da cânula de antibiótico nos tetos na secagem da vaca. A alta variação da CCS (608.000± 967.000 células/ml) sugere que outros fatores, como o número de quartos mamários infectados e os patógenos envolvidos, podem ter influenciado os resultados. A metodologia utilizada não permitiu identificar todos os fatores que poderiam aumentar a CCS. Contudo, os resultados são úteis para aprimorar os programas de controle da mastite.

Risk factors associated with subclinical mastitis in dairy cows on Swiss organic and conventional production system farms

Epidemiological studies comparing risk factors for subclinical mastitis (SM) in organic (OP) and conventional dairy production systems (CP) are lacking. In 60 OP and 60 CP farms, 970 cows were used to study risk factors for SM at 31 days postpartum. Cows showing a positive (≥ 1+) California Mastitis Test (CMT) in at least one quarter, but without clinical symptoms, were classified SM-positive. For OP cows increased (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) odds ratios (OR) for SM were found for other than Simmental and Simmental × Red Holstein breeds, for increasing number (&gt; 27) of cattle on the farm, for the use of mineral feed supplements, for irregular milking intervals (&lt; 12 and &gt; 12 h/day), and for milk urea concentrations of 210.1–270 mg/dl, whereas decreased OR for SM were recorded for cows kept in barns on beddings other than on rubber mats or concrete, for farms with rinsing water temperatures of milking systems between 54.75 and 60°C, for milk lactose &gt; 50.5 g/l, and for blood albumin levels of ł 38.5 g/l. For cows on CP farms, increased (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) OR for SM were found for other than Simmental ´ Red Holstein and Simmental breeds, for a bedding area width of &gt; 117 cm, and for antibiotic mastitis treatment since the last dry period, whereas reduced (&lt;I&gt;P&lt;/I&gt; &lt; 0.05) OR for SM were found for farms with a moderate (in contrast to good) hygiene status and for routine application of antibiotics during the dry period. Observed differences between OP and CP were assumed to be partially related to system-specific management, such as antibiotic dry cow therapy, nutrition and milking routine.

Risk Factors for Peripartum Mastitis in Pasture-Grazed Dairy Heifers

A longitudinal observational field study was conducted using 708 heifers in 30 spring-calving dairy herds in the Waikato region of New Zealand. The aim of the study was to investigate risk factors for subclinical and clinical mastitis (CM) in the peripartum period using path analysis methods and to find the factors most important at the population level as a basis for potential control programs. Body condition and udder hygiene scores, blood samples, and quarter mammary secretion samples for bacteriology were collected approximately 3 wk before the planned start of the seasonal calving period and again within 5 d following calving. Additionally, milk samples were collected from quarters diagnosed with CM within 14 d of calving. Significant risk factors for subclinical mastitis postcalving were precalving subclinical mastitis (3.32 incidence risk ratio; IRR), low minimum teat height above the ground (1.32 IRR), and unhygienic udder postcalving (1.32 IRR). Significant risk factors for clinical mastitis postcalving were precalving subclinical mastitis (2.14 IRR), Friesian breed (1.94 IRR), low minimum teat height above the ground (2.05 IRR), udder edema (1.81 IRR), and low postcalving nonesterified fatty acid serum concentration (1.55 IRR). Control of precalving subclinical mastitis and udder edema by producers, and enhancement of breed immunity by geneticists were important factors at a population level, and hence, are likely the most rewarding areas to target in any heifer mastitis management program.

Risk factors for subclinical mastitis among HIV‐infected and uninfected women in Lusaka, Zambia

Subclinical mastitis, defined as raised milk sodium/potassium (Na/K) ratio, is associated with poor infant growth and, among HIV-infected women, with increased milk HIV viral load. We conducted a longitudinal cohort study in Lusaka, Zambia, in order to investigate the relative importance of several potential causes of subclinical mastitis: maternal infection, micronutrient deficiencies and poor lactation practice. Women (198 HIV-infected, 189 HIV-uninfected) were recruited at 34 weeks' gestation and followed up to 16 weeks postpartum for collection of information on their health, their infant's health, infant growth and infant feeding practices. Milk samples were collected from each breast at 11 postpartum visits and blood at recruitment and 6 weeks postpartum. The geometric mean milk Na/K ratio and the proportion of women with Na/K ratio > 1.0 in one or both breasts were significantly higher among HIV-infected than among uninfected women. Other factors associated with the higher mean Na/K ratio in univariable analyses were primiparity, high maternal alpha(1)-acid glycoprotein (AGP) at 6 weeks, maternal overall morbidity and specific breast symptoms, preterm delivery, low infant weight or length, infant thrush and non-exclusive breast feeding. In multivariable analyses, primiparity, preterm delivery, breast symptoms, HIV status and raised AGP were associated with the raised Na/K ratio. Thus the main factors associated with subclinical mastitis that are amenable to intervention are poor maternal overall health and breast health. The impact of improved postpartum health care, especially management of maternal infections and especially in primiparous women, on the prevalence of subclinical mastitis and its consequences requires investigation.

Udder health and risk factors for subclinical mastitis in organic dairy farms in Switzerland

A study was performed in 1997 to estimate the prevalence and to investigate the etiology of subclinical mastitis in Swiss dairy herds managed under guidelines of controlled organic farming. It was planned as a longitudinal study over a period of 1 year and included a stratified random sample of 152 certified organic farms and 1907 cows. Two farm visits (the first from June to October when cows were on pasture, the second from January to March when cows were confined to barns) were performed on each farm. At each visit, farm management and individual-cow data (with emphasis on milking procedures and udder sanitation) were recorded. California mastitis tests (CMTs) were performed on each udder quarter of all cows in lactation. Milk samples with CMT >1+ were submitted for somatic cell counting (SCC), bacteriological examination and to test for antibiotic susceptibility. The SCC and germ-cell counts of monthly bulk-tank milk samples were available through Dairy Inspection and Advisory Services and milk production data of 567 herd-book cows were available from breeding associations. Possible individual and environmental predictors of subclinical mastitis were identified using logistic models adjusted for clustering of the data at herd and cow levels. Data were analyzed separately for cows from 7 to 100 and from 101 to 305 days post partum. Prevalences of subclinical mastitis at the quarter level were 21.2% for lactation period 7–100 days and 34.5% for 101–305 days post partum. The geometric mean SCC in bulk-tank milk samples was 85.6×10 3 cells/ml. Samples at 7–100 and 101–305 days post partum were positive for Staphylococcus aureus in 16.0 and 7.4%, for coagulase-negative Staphylococci in 51.5 and 50.6%, for Streptococcus agalactiae in 0.0 and 0.8%, for other Streptococci in 19.4 and 15.6%, for E. coli in 1.0 and 0.4%, and for Corynebacterium bovis in 25.7 and 45.1%, respectively. Risks of subclinical mastitis increased significantly with increasing days post partum and advancing age of cow. Cows that were sampled when staying in alpine dairies had considerably higher risks of subclinical mastitis than cows staying in home barns. Significantly lower risks of subclinical mastitis were observed in farms where CMT was performed regularly as a control measure. Bacteria in milk from cows with mastitis exhibited antibiotic resistance at a comparable frequency as found previously in conventional farms.