Costs and feasibility of extensive sample collection and processing are major obstacles to mastitis epidemiology research. Studies are often consequentially limited, and fundamental mastitis researchers rarely have the opportunity to conduct their work in epidemiologically valid populations. To mitigate these limitations, the Canadian Bovine Mastitis Research Network has optimized research funds by creating a data collection platform to provide epidemiologically meaningful data for several simultaneous research endeavors. This platform consists of a National Cohort of Dairy Farms (NCDF), Mastitis Laboratory Network, and Mastitis Pathogen Culture Collection. This paper describes the implementation and operation of the NCDF, explains its sampling protocols and data collection, and documents characteristics, strengths and limitations of these data for current and potential users. The NCDF comprises 91 commercial dairy farms in 6 provinces sampled over a 2-yr period. Primarily Holstein-Friesian herds participating in Dairy Herd Improvement milk recording were selected in order to achieve a uniform distribution among 3 strata of bulk tank somatic cell counts and to reflect regional proportions of freestall housing systems. Standardized protocols were implemented for repeated milk samplings on clinical mastitis cases, fresh and randomly selected lactating cows, and cows at dry-off and after calving. Just fewer than 133,000 milk samples were collected. Demographic and production data were recorded at individual cow and farm levels. Health management data are documented and extensive questionnaire data detailing farm management and cleanliness information are also captured. The Laboratory Network represents coordinated regional mastitis bacteriology laboratories using standardized procedures. The Culture Collection archives isolates recovered from intramammary infections of cows in the NCDF and contains over 16,500 isolates, all epidemiologically cross-referenced between linked databases. The NCDF is similar to Canadian dairies in relation to mean herd size, average production, and freestall percentages. Pathogen recovery was greater than anticipated, particularly for coagulase-negative staphylococci and Corynebacterium spp. International scientists are encouraged to use this extensive archive of data and material to enhance their own mastitis research.

Staphylococcus aureus intramammary infections (IMI) are a major cause of mastitis on farms worldwide. Incidence and elimination rates are the key determinants of prevalence of Staph. aureus, and risk factors associated with these rates must be identified, prioritized, and controlled to obtain long-term reduction in prevalence. The objectives of this study were to identify manageable risk factors associated with the lactational incidence, elimination, and prevalence of Staph. aureus IMI. A cohort of 90 Canadian dairy farms was recruited and followed in 2007 and 2008. Quarter milk samples were collected repeatedly from a selection of cows, and bacteriological culture was realized to assess incidence, elimination, and prevalence of Staph. aureus IMI. Practices used on farms were measured using direct observations and a validated questionnaire. A linear regression model was used to explore the relationship between herd IMI prevalence and incidence and elimination rates. Multilevel logistic regression models were used to compute measures of associations between practices used on farms and IMI incidence, elimination, and prevalence. The herd incidence rate was the most important predictor of herd IMI prevalence: a reduction of the incidence rate equivalent to its interquartile range (0.011 new IMI/quarter-month) was associated with a prevalence reduction of 2.2 percentage points; in comparison, an equivalent increase of the elimination rate by its interquartile range (0.36 eliminated IMI/quarter-month) resulted in a prevalence reduction of 0.4 percentage points. Postmilking teat disinfection and blanket dry-cow therapy were already implemented by most herds. Most of the practices associated with Staph. aureus IMI incidence were related to milking procedures. Among these, wearing gloves during milking showed desirable associations with IMI incidence, elimination, and prevalence. Similarly, adequate teat-end condition and use of premilking teat disinfection were associated with lower IMI incidence and prevalence. The initial herd prevalence of Staph. aureus IMI was positively associated with subsequent IMI incidence. This indicates that, in some situations, an initial reduction of the pool of infected quarters could be justified. Some housing practices were associated with IMI incidence, elimination, or prevalence. The effects of these latter practices, however, were often influenced by specific cow characteristics such as parity or days in milk. These results highlight the importance of good milking practices to prevent Staph. aureus IMI acquisition and, therefore, reduce their prevalence.

Achieving herd health and welfare improvement increasingly relies on cattle veterinarians to train and advise farmers, placing veterinary interactions at the heart of knowledge exchange. Cattle veterinarians recognize their influence and the need to be proactive advisors but struggle with acting upon this awareness in daily practice, reporting a need to enhance their advisory approach to inspire farmer behavior change. Understanding how veterinarian-farmer interactions positively or negatively influence the enactment of change on farm is therefore essential to support the cattle veterinary profession. This paper adopts a qualitative approach to conceptualize how and under what circumstances veterinary advice has the potential to support and inspire farmer engagement with behavior change on the UK dairy farm. Fourteen UK dairy farms were recruited to take part in a qualitative study involving research observation of a typical advisory consultation between veterinarian and farmer (n = 14) followed by separate, in-depth interviews with the farmer(s) and their respective veterinarian. Interview data were organized using a template coding method and analyzed thematically. While accuracy of veterinary advisory content was valued, it was a relational context of trust, shared veterinarian-farmer understanding, and meaningful interpretation of advice at a local (farmer) level that was most likely to enact change. Critically, these relational factors were reported to work together synergistically; a trusting relationship was an essential, but not necessarily sufficient, component to create a culture of change. Findings suggest that cattle veterinarians may benefit from tailoring advisory services to the farmer's specific world view, facilitated by a shared understanding of the farmer's immediate and long-term motivational drivers. In consequence, cattle veterinarians seeking to positively engage farmers in advisory interactions could consider a focus on farmer priorities, motivations, and goals as paramount to frame and inform advisory messages. This explicit collaborative communication encourages the selection of appropriate and timely veterinary expertise, leading to better integration and adoption of advice on farm given enhanced advisory relevance for farmers' unique circumstances. This farmer-centered approach, involving active co-creation of plans between individuals, is critical for engagement and commitment when tackling complex problems.

Composite milk samples, in which milk from all 4 bovine quarters is collected in a single vial, are widely used in many developed dairy industries for detection of intramammary infections (IMI). These samples are more economical for use in culturing protocols than individual quarter samples, and may be useful when considering management options at the cow and herd level. The dilution effect may be problematic, however, resulting in lower sensitivity (Se) in IMI detection on composite samples. Relative Se and specificity (Sp) in composite samples have previously been described for some major pathogens, but because the causative organism for IMI is initially unknown, it is beneficial to investigate the reliability of composite samples for detection of all types of mastitis-causing bacteria. The Canadian Bovine Mastitis Research Network has a large data collection platform-the National Cohort of Dairy Farms-containing a vast amount of data on mastitis in Canada. These data have been used to further investigate the Se and Sp of composite samples in detecting IMI caused by specific mastitis pathogens. Milk samplings of selected cows before dry-off, after calving, and during lactation (n=48,835 samples) were employed to this end. Composite samples showed moderately high Se for Staphylococcus aureus (77.1%, 95% CI=73.3-80.5) and Streptococcus dysgalactiae (73.4%, 95% CI=60.9-83.7), with moderate Se for Streptococcus uberis (62.1%, 95% CI=49.3-73.8) and coagulase-negative staphylococci (59.8%, 95% CI=58.4-61.2). Sensitivities always increased as the number of affected quarters increased. Composite samples also showed high Sp (>97%) for most organisms. Factors such as lactation number and stage of lactation were evaluated for their influence on the Se and Sp of composite sampling, but were only found to be significant for coagulase-negative staphylococci. Predictive values using the herd prevalences found across Canada were calculated and can be useful in field scenarios when composite sampling is employed to assist mastitis management. When used to detect newly occurring IMI in pairs of samples taken before dry-off, post-calving, and also prior to and subsequent to the dry period, composite samples were shown to have lower Se but similar Sp for all pathogens investigated. Composite samples can be used to detect IMI and new IMI in dairy cows, but the Se and Sp of the procedure should be taken into account.

The problem of nonadherence to advice is recognized in several professional relationships, including the veterinarian-client relationship. A better understanding of farmer perspectives may help to improve efficiency in veterinary herd health management. This study aimed to qualitatively and quantitatively describe farmers' reasons for adherence and nonadherence with veterinary recommendations regarding preventive herd health measures. We carried out structured telephone interviews about implementation of preventive measures with owners or staff of 163 dairy farms and 6 beef farms. The farms had received an advisory visit by their veterinarian (n = 36), who had documented the preventive measures they had recommended. The interviewer noted verbatim responses to reasons for implementing preventive measures fully, partially, or not at all, and we analyzed these responses thematically. We also conducted a quantitative analysis, in which we calculated descriptive statistics of the proportions of different categories of reasons stated by the farmers. Altogether, 726 preventive measures (range per farm 1 to 17; median 3; interquartile range 2 to 6) were documented. We identified 3 organizing themes related to adherence or nonadherence with veterinary advice: trust, feasibility, and priorities. Overall, the most commonly stated reasons related to trust (in the veterinarian, in the advisory process, or in individual preventive measures). The most common reasons not to follow the recommended advice were related to feasibility. Based on the results, we recommend that, to improve adherence to their advice, veterinarians pay increased attention to farmers' needs, priorities, goals, and motives, as well as to farmers' perceptions of the effectiveness of individual preventive measures. We also recommend that veterinarians need to increase their focus on recommending preventive measures that are practically feasible to implement on farms.

Farmer-led, participatory approaches are being increasingly employed in agricultural research, with promising results. This study aimed to understand how a participatory approach based on the Danish stable schools could help to achieve practical, farmer-led changes that reduced reliance on antimicrobials in the UK. Five facilitated farmer action groups comprising 30 dairy farms across South West England met on farm at regular intervals between 2016 and 2018, and worked collaboratively within their groups to discuss how to reduce antimicrobial use. Qualitative data from group discussions and individual semi-structured interviews were collected and analyzed using thematic analysis to explore how the approach helped farmers address and deal with changes to their on-farm practices. Facilitator-guided reviews of antimicrobial use and benchmarking were carried out on each farm to assess any change in usage and help farmers review their practices. The pattern of antimicrobial use changed over the 2 yr of the study, with 21 participating farms reducing their use of highest-priority critically important antibiotics (6 farms were not using any of these critical medicines from the outset). Thirty practical action plans were co-developed by the groups with an average implementation rate of 54.3% within a year. All assessed farms implemented 1 recommendation, and many were still ongoing at the end of the study. Farmers particularly valued the peer-to-peer learning during farm walks. Farmers reported how facilitated discussions and action planning as a peer group had empowered them to change practices. Participants identified knowledge gaps during the project, particularly on highest-priority critically important antibiotics, where they were not getting information from their veterinarians. The study demonstrated that facilitation has a valuable role to play in participatory approaches beyond moderating discussion; facilitators encouraged knowledge mobilization within the groups and were participants in the research as well. Facilitated, farmer-led, participatory approaches that mobilize different forms of knowledge and encourage peer learning are a promising way of helping farmers to adapt and develop responsible practices.