Abstract The control of mastitis remains a focus of attention for dairy farmers, veterinary surgeons and advisors due to its impact on cow health and welfare, milk quality, sustainable production, and the financial costs associated with treatment, prevention and ongoing control. In addition, the focus on the unnecessary use of antibiotics in agriculture has meant that mastitis control in dairy herds has received renewed interest, particularly around prevention of new infection and alternative treatment strategies. The latter includes the selective use of intra-mammary antibiotic for infected cows at drying-off, reserving parenteral antibiotic for clinical cases where the cow is ill, and selecting intra-mammary antibiotic treatment for clinical mastitis based on culture results. Treating clinical mastitis caused by Gram-positive pathogens such as Streptococcus spp. with intra-mammary antibiotic remains important to optimise chance of cure and reduce risk of transmission of infection, although antibiotics may not be required for clinical mastitis infections caused by other pathogens, particularly E. coli . The long-term reduction and rationalisation of antibiotic use in mastitis control is achieved through improved management to prevent new infections and avoid the need to treat mastitis. This comes through understanding the predominant epidemiological ‘pattern’ of infection in the herd and targeted implementation of well-specified interventions to reduce the rate of new infection, either in lactation or during the dry period. For most dairy herds, environmental mastitis pathogens predominate and therefore management and hygiene of housed and pastured environments is a key component of mastitis control plans designed to reduce the need to use antibiotics in mastitis control.

Selective use of antibiotic dry cow treatment can be implemented at the cow or quarter level, with the latter having the potential to further reduce antibiotic use. Our objective was to compare these 2 approaches in 6 herds in the United Kingdom in which environmental mastitis predominated. Eight hundred seven cows were enrolled and categorized as having a high cell count (n = 401) or low cell count (n = 406) in the last 3 mo of lactation and clinical mastitis history. All quarters of all enrolled cows received an internal teat sealant. Within each category, cows were randomly allocated to 1 of 3 groups; in one group antibiotic treatment was allocated at cow level (i.e., all 4 quarters received antibiotic), whereas in the 2 remaining groups antibiotic treatment was allocated at quarter level, based on California Mastitis Test (CMT) findings. Two different thresholds, score 1 and 2, were used to determine likely infection status. Quarter milk samples were collected at dry off and postcalving for bacteriological culture and somatic cell count (SCC). Cows were monitored for clinical mastitis from dry off until 100 d in milk. Cow level SCC and milk yield data were collated from farm records. Within each category, the 2 quarter level treatment groups were compared with cow level treatment at dry off. Leaving quarters untreated with intramammary antibiotic in cows in the high cell count group, with a CMT <2 or <1, reduced antibiotic use by 55% and 31%, respectively, and resulted in no difference in the odds of being infected with any pathogen postcalving, but was associated with a higher SCC at the first test day. Intramammary antibiotic treatment of quarters with a CMT ≥1 in cows in the low cell count category at dry off was not associated with any reduction in the odds of being infected with a major pathogen postcalving but was associated with a decrease in the odds of being infected with a minor mastitis pathogen postcalving. The use of antibiotics in quarters of cows categorized as low cell count at dry off, increased the proportion of quarters treated with antibiotic from 0% at cow level to 31% (CMT ≥ 1) and 12% (CMT ≥ 2) at quarter level, only resulting in a reduction in SCC of around 20,000 cells/mL at the first test day, if all quarters with CMT score ≥1 were treated with antibiotic. No differences in clinical mastitis incidence and milk yield in the first 100 d in milk were detected between any of the treatment groups. These study findings support selective quarter level dry off treatment only in cows with cow level SCC >200,000 cells/mL at dry off.

Mastitis in dairy cattle is extremely costly both in economic and welfare terms and is one of the most significant drivers of antimicrobial usage in dairy cattle. A critical step in the prevention of mastitis is the diagnosis of the predominant route of transmission of pathogens into either contagious (CONT) or environmental (ENV), with environmental being further subdivided as transmission during either the nonlactating "dry" period (EDP) or lactating period (EL). Using data from 1000 farms, random forest algorithms were able to replicate the complex herd level diagnoses made by specialist veterinary clinicians with a high degree of accuracy. An accuracy of 98%, positive predictive value (PPV) of 86% and negative predictive value (NPV) of 99% was achieved for the diagnosis of CONT vs ENV (with CONT as a "positive" diagnosis), and an accuracy of 78%, PPV of 76% and NPV of 81% for the diagnosis of EDP vs EL (with EDP as a "positive" diagnosis). An accurate, automated mastitis diagnosis tool has great potential to aid non-specialist veterinary clinicians to make a rapid herd level diagnosis and promptly implement appropriate control measures for an extremely damaging disease in terms of animal health, productivity, welfare and antimicrobial use.

The introduction of bedding dairy cows on recycled manure solids (RMS) in the UK led to concern by competent authorities that there could be an increased, unacceptable risk to animal and human health. A cross-sectional study was designed to evaluate the microbial content of different bedding materials, when used by dairy cows, and its impact on the microbial content of milk. Data were collected from farms bedding lactating cows on sand (n = 41), sawdust (n = 44) and RMS (n = 40). The mean duration of RMS use prior to sampling was 13 months. Total bacterial count, and counts of Streptococcus/Enterococcus spp., Staphylococcus spp., Bacillus cereus, thermophilic, thermoduric and psychrotrophic bacteria were determined in used bedding and milk. Samples were evaluated for the presence/absence of Listeria monocytogenes, Salmonella spp. and Yersinia enterocolitica. Data on milking practices were collected to investigate their potential to reduce microbial transfer from bedding to milk. There were substantial differences in bacterial counts both within and between bedding materials. However, there were no significant differences between bedding groups in counts in milk for any of the organisms studied, and no significant correlations between bacterial load in used bedding and milk. Fore-milking was associated with a reduced total bacterial count in milk. Dipping teats with disinfectant and drying, prior to milking, was associated with lower numbers of Streptococcus/Enterococcus spp. in milk. Disinfecting clusters between milking different cows was associated with a reduction in thermophilic and psychrotrophic counts in milk. This study did not provide evidence that use of RMS bedding increased the risk of presence of Y. enterocolitica, Salmonella spp. or L. monocytogenes in milk. However, the strength of this conclusion should be tempered by the relatively small number of farms on which Y. enterocolitica and Salmonella spp. were isolated. It is concluded that, despite the higher bacterial load of RMS, its use as bedding for lactating dairy cows need not be associated with a higher bacterial load in milk than the use of sand or sawdust. However, this finding must be interpreted in the light of the relatively recent introduction of RMS as a bedding material on the farms studied. Teat preparation provides a control point for the potential transfer of microorganisms from bedding to milk. The detection of zoonotic pathogens in a small proportion of milk samples, independent of bedding type, indicates that pasteurisation of milk prior to human consumption remains an important control measure.

A concerted effort to improve mastitis control will form an important aspect of the industry's approach to reaching the RUMA antimicrobial use targets. It is now widely accepted that it is vital to reduce antimicrobial use through mastitis prevention, rather than simply changing antimicrobial prescription practices. Whilst a proven approach to mastitis control exists (the AHDB Mastitis Control Plan), it has been recognised by an industry forum that a "lower" or "entry level" approach would be beneficial and cost effective on many farms. A new initiative ("Quarter PRO") is proposed, which aims to provide and promote a rapid approach to monitoring and improving udder health; accessible to all dairy farmers. The approach provides a four-step iterative process for identifying a herd's "mastitis pattern" and providing support to optimise udder health: 1. Automated data analysis identify,ingandranking farm specific mastitis issues. 2. Identification of key management areas related to.these issues. 3. Use of resources to identify relevant actions. 4. Quarterly reassessment. This initiative will provide wider and easier access to elements of the AHDB Mastitis Control Plan and a means of co-ordinating udder health promotion materials. It is hoped that it will attract further widespread support across the industry.

The objective of this study was to use probabilistic sensitivity analysis to evaluate the cost-effectiveness of using an on-farm culture (OFC) approach to the treatment of clinical mastitis in dairy cows and compare this to a 'standard' treatment approach. A specific aim was to identify the herd circumstances under which an OFC approach would be most likely to be cost-effective. A stochastic Monte Carlo model was developed to simulate 5000 cases of clinical mastitis at the cow level and to calculate the associated costs simultaneously when treated according to 2 different treatment protocols; i) a 'conventional' approach (3 tubes of intramammary antibiotic) and ii) an OFC programme, whereby cows are treated according to the results of OFC. Model parameters were taken from recent peer reviewed literature on the use of OFC prior to treatment of clinical mastitis. Spearman rank correlation coefficients were used to evaluate the relationships between model input values and the estimated difference in cost between the standard and OFC treatment protocols. The simulation analyses revealed that both the difference in the bacteriological cure rate due to a delay in treatment when using OFC and the proportion of Gram-positive cases that occur on a dairy unit would have a fundamental impact on whether OFC would be cost-effective. The results of this study illustrated that an OFC approach for the treatment of clinical mastitis would probably not be cost-effective in many circumstances, in particular, not those in which Gram-positive pathogens were responsible for more than 20% of all clinical cases. The results highlight an ethical dilemma surrounding reduced use of antimicrobials for clinical mastitis since it may be associated with financial losses and poorer cow welfare in many instances.

Mastitis in dairy herds continues to be important and relevant to veterinary advisors for many reasons, including cow welfare, cost of disease and sustainability of farming and food supply, environmental impact, wastage and use of antimicrobials. When implementing control measures to reduce mastitis infection rates on farm, the importance of a herd level analysis of patterns to inform decision making has been shown to be a crucial step. Although the AHDB Dairy Mastitis Control Plan has performed well since its inception, feedback from participants and businesses indicate that the first stage of the Plan, analysing patterns and making a herd 'diagnosis' is often a difficult stage for Plan Deliverers. Analysis of data using software and understanding of mastitis epidemiology remain barriers to more widespread control of mastitis in the UK. This project aims to provide a fully automated method of assessing the predominant mastitis infection patterns present on farm, using somatic cell count and clinical mastitis records. Importantly, this automated tool will enable mastitis control Plan Deliverers and farmers to immediately highlight the most important areas on their unit for mastitis control and direct efforts accordingly.

Antimicrobial resistance has been reported to represent a growing threat to both human and animal health, and concerns have been raised around levels of antimicrobial usage (AMU) within the livestock industry. To provide a benchmark for dairy cattle AMU and identify factors associated with high AMU, data from a convenience sample of 358 dairy farms were analysed using both mass-based and dose-based metrics following standard methodologies proposed by the European Surveillance of Veterinary Antimicrobial Consumption project. Metrics calculated were mass (mg) of antimicrobial active ingredient per population correction unit (mg/PCU), defined daily doses (DDDvet) and defined course doses (DCDvet). AMU on dairy farms ranged from 0.36 to 97.79 mg/PCU, with a median and mean of 15.97 and 20.62 mg/PCU, respectively. Dose-based analysis ranged from 0.05 to 20.29 DDDvet, with a median and mean of 4.03 and 4.60 DDDvet, respectively. Multivariable analysis highlighted that usage of antibiotics via oral and footbath routes increased the odds of a farm being in the top quartile (>27.9 mg/PCU) of antimicrobial users. While dairy cattle farm AMU appeared to be lower than UK livestock average, there were a selection of outlying farms with extremely high AMU, with the top 25 per cent of farms contributing greater than 50 per cent of AMU by mass. Identification of these high use farms may enable targeted AMU reduction strategies and facilitate a significant reduction in overall dairy cattle AMU.

Importance of the dry period with respect to mastitis control is now well established although the precise interventions that reduce the risk of acquiring intramammary infections during this time are not clearly understood. There are very few intervention studies that have measured the clinical efficacy of specific mastitis interventions within a cost-effectiveness framework so there remains a large degree of uncertainty about the impact of a specific intervention and its costeffectiveness. The aim of this study was to use a Bayesian framework to investigate the cost-effectiveness of mastitis controls during the dry period. Data were assimilated from 77 UK dairy farms that participated in a British national mastitis control programme during 2009–2012 in which the majority of intramammary infections were acquired during the dry period. The data consisted of clinical mastitis (CM) and somatic cell count (SCC) records, herd management practices and details of interventions that were implemented by the farmer as part of the control plan. The outcomes used to measure the effectiveness of the interventions were i) changes in the incidence rate of clinical mastitis during the first 30 days after calving and ii) the rate at which cows gained new infections during the dry period (measured by SCC changes across the dry period from <200,000 cells/ml to >200,000 cells/ml). A Bayesian one-step microsimulation model was constructed such that posterior predictions from the model incorporated uncertainty in all parameters. The incremental net benefit was calculated across 10,000 Markov chain Monte Carlo iterations, to estimate the cost-benefit (and associated uncertainty) of each mastitis intervention. Interventions identified as being cost-effective in most circumstances included selecting dry-cow therapy at the cow level, dry-cow rations formulated by a qualified nutritionist, use of individual calving pens, first milking cows within 24 h of calving and spreading bedding evenly in dry-cow yards. The results of this study highlighted the efficacy of specific mastitis interventions in UK conditions which, when incorporated into a costeffectiveness framework, can be used to optimize decision making in mastitis control. This intervention study provides an example of how an intuitive and clinically useful Bayesian approach can be used to form the basis of an on-farm decision support tool.

Beef suckler cow calf farms similarly to firms in other sectors of production operate in competitive and dynamically changing environments. In order to increase profitability and reduce uncertainty, beef suckler cow calf farmers may not be able to change radically their farm resources in the short-run; however they can decide on either retaining or not the ownership of calves. This decision brings changes to the herd size and composition, and ultimately defines the degree of farm’s market integration. Flexibility is a measure of firm’s competitive advantage which reflects its capacity to cope with uncertainty. In this paper two types of flexibility have been estimated, and its determinants have been identified for three cow calf systems. Namely, tactical flexibility indicates farmer’s ability to vary output level in the medium-run, and operational flexibility reflects the ability to adjust product mix in the short-run. In these systems farmer’s decision and time-length to retain their calves differs, thus farm’s flexibility is examined in relation to varying calf retention decisions. Results indicate that calf to weaning farms who retain the ownership of their calves beyond weaning increase both tactical and operational flexibility. Adjustments in cattle marketing strategies increase the flexibility of all beef farms.

The objectives of this study were to report performance and management data taken from a sample of UK dairy farms that have participated in the Agriculture and Horticulture Development Board Dairy Mastitis Control Plan (DMCP) and to identify important mastitis prevention practices that are not currently widely implemented. A total of 234 UK dairy herds were included in the study from which farm management and udder health data were collected. Herds were grouped according to their mastitis epidemiology and could be classed as (i) environmental dry period (EDP) (i.e. environmental pathogen with majority of infections being acquired during the dry period), (ii) environmental lactation (EL), (iii) contagious dry period (CDP) or (iv) contagious lactation (CL). The results of this study showed that many mastitis-related management practices that are generally considered to be important were not widely performed. A better understanding of those practices not widely adopted by UK dairy farmers at present may aid practitioners in identifying and overcoming potential barriers to improved mastitis control.

Mastitis caused by intramammary infections of environmental origin has become the dominant udder health ‘pattern’ for dairy herds in the UK and many other countries, compared with the situation 40–50 years ago when contagious mastitis patterns predominated. The diagnosis of environmental mastitis in dairy herds requires epidemiological data from clinical mastitis cases and individual cow somatic cell count (SCC) data as well as information regarding likely aetiology from samples submitted for bacteriology. This article reviews the diagnosis of environmental mastitis caused by intramammary infections of lactating period origin, and examples of patterns to illustrate these herd patterns.

Probabilistic sensitivity analysis (PSA) is a simulation-based technique for evaluating the relative importance of different inputs to a complex process model. It is commonly employed in decision analysis and for evaluation of the potential impact of uncertainty in research findings on clinical practice, but has a wide variety of other possible applications. In this example, it was used to evaluate the association between herd-level udder health and reproductive performance in dairy herds. Although several recent studies have found relatively large associations between mastitis and fertility at the level of individual inseminations or lactations, the current study demonstrated that herd-level intramammary infection status is highly unlikely to have a clinically significant impact on the overall reproductive performance of a dairy herd under typical conditions. For example, a large increase in incidence rate of clinical mastitis (from 92 to 131 cases per 100 cows per year) would be expected to increase a herd's modified FERTEX score (a cost-based measure of overall reproductive performance) by just £4.50(1) per cow per year. The herd's background level of submission rate (proportion of eligible cows served every 21 days) and pregnancy risk (proportion of inseminations leading to a pregnancy) correlated strongly with overall reproductive performance and explained a large proportion of the between-herd variation in performance. PSA proved to be a highly useful technique to aid understanding of results from a complex statistical model, and has great potential for a wide variety of applications within the field of veterinary science.

Material obtained from physical separation of slurry (recycled manure solids; RMS) has been used as bedding for dairy cows in dry climates in the US since the 1970s. Relatively recently, the technical ability to produce drier material has led to adoption of the practice in Europe under different climatic conditions. This review collates the evidence available on benefits and risks of using RMS bedding on dairy farms, with a European context in mind. There was less evidence than expected for anecdotal claims of improved cow comfort. Among animal health risks, only udder health has received appreciable attention. There are some circumstantial reports of difficulties of maintaining udder health on RMS, but no large scale or long term studies of effects on clinical and subclinical mastitis have been published. Existing reports do not give consistent evidence of inevitable problems, nor is there any information on clinical implications for other diseases. The scientific basis for guidelines on management of RMS bedding is limited. Decisions on optimum treatment and management may present conflicts between controls of different groups of organisms. There is no information on the influence that such 'recycling' of manure may have on pathogen virulence. The possibility of influence on genetic material conveying antimicrobial resistance is a concern, but little understood. Should UK or other non-US farmers adopt RMS, they are advised to do so with caution, apply the required strategies for risk mitigation, maintain strict hygiene of bed management and milking practices and closely monitor the effects on herd health.

This paper is produced directly from the Executive Summary of the Final Report of a project funded by DairyCo. entitled "Scoping Study on the Potential Risks (and Benefits) of using Recycled Manure Solids as Bedding for Dairy Cattle". The report summarises information available from peer reviewed literature, conference proceedings, research reports, and a survey of UK users of recycled manure solids as bedding, and is available in full at www.dairyco.org.uk/resources-library/technical-information/buildings/rms-beddingM.U7ZfX_IdXNs. More information including FAQ and the current position with respect to Recycled Manure Solids bedding is available at www.dairyco.org.uk/technical-information/buildings/housing/recycled-manuresolids/#.U7ZfZvIdXNu.

Vaccination can play a useful role in mastitis control programs, although there is a relative dearth of large, well-controlled field efficacy studies. This paper presents the findings on the use of a commercially available vaccine (Startvac, Hipra UK Ltd., Nottingham, UK) on commercial units under UK field conditions. In total, 3,130 cows were recruited from 7 farms and were randomly allocated, within farm, to 1 of 3 groups. The first group received the vaccine following the label regimen, the second group was vaccinated every 90 d following an initial vaccination course, and the third group was left unvaccinated to act as controls. Vaccine efficacy was assessed in the first 120 d of lactation. Data were available for analysis from 1,696 lactations in 1,549 cows. In total, 779 cases of clinical mastitis occurred in the 3 study groups, and we detected no significant difference in the incidence or prevalence of clinical or subclinical mastitis between any of the 3 groups. Mastitis vaccination following the label regimen was associated with a significant reduction in the severity of clinical cases. Cows in this group were at significantly decreased odds of developing clinical mastitis presenting with more than just milk changes [odds ratio: 0.58; 95% confidence interval (CI): 0.35-0.98]. Similarly, each additional vaccination resulted in a cow being at decreased odds of developing clinical mastitis presenting with more than just milk changes (odds ratio: 0.87; 95% CI: 0.77-0.98). Although no cows were culled because of severe mastitis in either of the vaccinated groups, we detected no significant difference in the mastitis-related culling rate between groups. Analysis of milk production data demonstrated that, on average, cows on the label regimen produced a higher volume of milk (231 L; 95% CI: 104.1-357.4) and more milk solids (12.36 kg; 95% CI: 3.12-21.60) than unvaccinated cows in the first 120 d of lactation. Conservative analysis suggested that a return on investment of 2.57:1 could be expected under UK conditions based on increased milk yield alone.