25 Jun 2018
Effective herd health planning – latest thinking and strategies
Katherine Fitzgerald looks at advances and key actions in dairy herd health to reduce disease and lessen antimicrobial use.

Image: Texturewall / Adobe Stock
This independent article is showcased and supported online by Vetspanel.
Vetspanel is a panel of veterinary professionals consisting of vets, vet nurses, and practice managers who share their opinions on a variety of issues.
The issues that impact dairy farming are numerous and diverse, from changes in consumer expectations, economic pressures and global issues, including emissions and antimicrobial resistance.
The concept of herd health planning too has adapted from a document that satisfies an assurance inspection to a dynamic process that involves vet and farmer engaging with the issues that limit the health and welfare of the cattle, and the productivity of the enterprise.
In recent years, the work of individual vets at the herd level has been matched by nationwide efforts to reduce disease, rationalise antimicrobial use and refine our processes through precision agriculture. This article discusses some of the key actions and advances in these areas.
Endemic disease update
Lameness
Relative risk (RR) and population attributable fraction (PAF) are used by epidemiologists to help understand how risk factors are related to incidents within a population. RR is a measure of association that describes the ratio of incidence of disease in a population exposed to a risk factor relative to the incidence in the unexposed population.
PAF is a measure of impact. It quantifies the extent to which a risk factor contributes to a disease. It can also be considered as the proportional reduction in population disease that would be seen if the risk factor was removed. PAF depends not only on the increased risk associated with exposure, but is also directly related to the prevalence of exposure. Understanding the PAF of risk factors can help vets and farmers prioritise changes towards areas that can maximise disease reduction.
The latest lameness research suggests early identification and treatment are pivotal in making inroads into reducing lameness prevalence in herds. However, research would suggest, when it comes to lameness, the concept prevention is better than cure may be more significant than previously thought. A study examined the population attributable fraction (PAF) of risk factors for lameness (Panel 1) and demonstrated a history of previous lameness was attributed to between 79% and 83% of lameness in the two herds studied (Randall et al, 2017). This suggests a large proportion of lameness can be accounted for by an accumulation of repeat cases. The challenge for vets is to identify why initial cases occur and how to prevent them.
Reproduction
Reproductive efficiency remains a key driver of dairy farm profitability and the cornerstone of dairy veterinary input. However, genetic selection for higher yield, and more persistent lactation profiles, have led some farmers to question whether a target of a calving interval of less than 385 days remains appropriate for modern Holstein cows.
Provisional results from work using simulation to examine how efficiently each “cow place” within the herd is used revealed, even when an updated lactation curve is accounted for, a cost-benefit of improving fertility can be seen. For example, an increase in 21-day pregnancy rate from 15% to 20% suggested a cost benefit in the region of £80 per cow per year (Hudson, 2018 – unpublished data). Hence, a clear role remains for the vet in driving 21-day pregnancy rate by identifying bottlenecks and working with farmers to reduce risk factors specific to their farms.
Mastitis
Selective dry cow therapy remains high on the agenda for many milk purchasers. Figures show somatic cell count in British dairies ranging from 150,000 cells/ml to 175,000 cells/ml, which shows, even with seasonal rises, our national herd prevalence of subclinical mastitis remains very low and it can no longer be considered rational to use blanket antibiotic dry cow therapy.

Internal teat sealants are considered significantly better at reducing new infections during the dry period and antibiotic use in low cell count cows increased the risk of coliform mastitis in the next lactation (Bradley et al, 2010).
Dairy vets have an opportunity to work with clients to optimise dry cow therapy protocols in a farm-specific manner. In high cell count herds, protocols should be optimised to prioritise treatment and a lower threshold for antibiotic treatment may be appropriate (for example, more than 100,000 cells/ml to 150,000 cells/ml). In lower cell count herds, we are aiming for higher specificity – hence, a higher antibiotic treatment threshold of 200,000 cells/ml to 250,000 cells/ml can be used.
National disease eradication programmes
In addition to reproduction, mastitis and lameness, infectious disease control represents a key area for veterinary engagement that can benefit the health and productivity of a herd. Dairy practitioners have both the detailed knowledge of disease epidemiology as well as a genuine understanding of farm management practices and are, hence, well placed to deliver targeted, farm-specific advice on disease control strategies.
While many practices have engaged with their clients in monitoring infectious disease status and reducing risk factors for infection, it is clear from lessons learned of successful infectious disease eradication programmes (for example, Norway, Sweden, Finland and Denmark have successfully eradicated bovine viral diarrhoea; BVD), coordinated national strategies are necessary.
BVDFree England
BVDFree England is a voluntary, industry-led scheme aiming to eliminate BVD from cattle in England by 2022. The scheme is built around a national database that documents the BVD status of individual animals and herds with the aim of providing farmers with recognition, confidence and traceability when buying and selling cattle. Vets are encouraged to work with their farms following the ADAM principle (Panel 2).
ASSESS the level of biosecurity and disease risk.
DEFINE the bovine viral diarrhoea (BVD) status through BVD antigen tag and test (for a minimum of two years) or antibody screening of unvaccinated youngstock.
ACTION plan for control – farm-specific control strategy. If active BVD is evident, identification and removal of persistently infected animals is key. If no evidence of active BVD exists, the plan should target controlling risk of introduction (samples must be sent to designated laboratories).
MONITOR progress. Youngstock screening every 7 to 12 months, or ongoing tag and testing plus testing any purchased animals.
Since the end of March 2018, herds have had the chance to apply for BVDFree Test Negative Herd Status, which signifies a herd has two years of negative test results. A veterinary declaration is required before the status can be awarded and vets signing the declaration must have completed the online training provided by the BCVA (https://bit.ly/2MmTGjz).
More than 150 vets have completed the training, and while many more will clearly be engaged in controlling BVD within their own practices, support of this scheme by vets and farmers would be a positive step towards the goal of BVDFree England.
Action Johne’s
The Action Group on Johne’s, a collaborative of industry stakeholders, is driving the Action Johne’s initiative. The initiative is focused on delivering the National Johne’s Management Plan (NJMP) and is focused on engaging farmers rather than surveillance. The strategic approach is based around six control strategies developed and endorsed by the group and encourages vets to engage with farmers to deliver the plans. More than 700 vets have taken up the online training provided by the action group in conjunction with BCVA to gain the status of BCVA-accredited Johne’s veterinary advisor (BAJVA).
Phase one, which commenced in April 2015, focused on education and engagement with the NJMP. A survey of 16 milk purchasers supporting the NJMP completed at the end of this phase reported 86% of respondents were undertaking Johne’s surveillance with 83% employing a control strategy. A total of 74% of respondents had discussed Johne’s disease risk with their vet, which is an encouraging figure, but suggests potential still exists for vets to actively engage with farmers – some of whom are already undertaking surveillance and control strategies without their involvement.

Phase two launched in February 2017 and aims to have engaged 95% of the dairy supply in Great Britain by December 2019. To date, 26 milk processors are supporting NJMP, representing 82% of Great Britain’s milk supply. By 31 October 2018, all farmers supplying purchaser members of NJMP must have assessed their risks and herd status, put a written management plan in place, and co-signed a declaration of compliance with their BAJVA. This gives vets a clear opportunity to offer a genuine consultancy service by combining their knowledge of the disease with their understanding of the risk factors associated with a specific farming enterprise.
Visit www.actionjohnesuk.org/bcva-johnes-training for more information on how to become a BAJVA.
Antibiotic use
The O’Neil report – commissioned in 2014 to analyse the global problem of antimicrobial resistance – identified reducing unnecessary use of antimicrobials in agriculture as a key intervention. This led to a target of reducing antimicrobial use in UK agriculture to 50mg per population corrected unit (PCU), which has been achieved ahead of schedule.
However, a study looking at antimicrobial use on UK dairy farms has shown the 25% highest-using farms account for 50% of the antibiotic use by mass (Hyde et al, 2017). This pattern of a small number of very high users was observed in all the veterinary practices that took part in this study, which suggests it is differences in the practices of individual farms, rather than differences in practice level prescribing habits, that led to this range.
A 100-cow dairy herd with an incidence of mastitis of 30 cases/100 cows/year, using selective dry cow therapy with 50% of cows receiving antibiotic tubes. The incidence of retained fetal membranes is 5 cases/100 cows/year, metritis is 15 cases/100 cows/year, endometritis is 20 cases/100 cows/year and left displaced abomasum is 5 cases/100 cows/year.
Figure 1 shows an estimated antimicrobial use for this herd of 32.5mg/population corrected unit (PCU) or a defined daily dose (DDD) of 3.67. Reducing the incidence of retained fetal membranes, metritis, endometritis and left-displaced abomasa to target levels could reduce antimicrobial use in mg/PCU by more than 50% and reduce DDD to 2.17 (Figure 2). DCD = defined course dose.
The Agriculture and Horticulture Development Board and the University of Nottingham have developed a tool to analyse antibiotic use at a farm level that can be used to monitor antibiotic use in your herds.
A benchmarking tool is also available (https://bit.ly/2GZBRHj) to help you identify candidates that may benefit from further intervention in preventive strategies for disease control. The strategies to reduce antimicrobial use will be highly farm-specific and will offer a different route into discussing aspects of herd health with clients.
However, several practices exist that increase the odds of a farm being in the top quartile. The use of antibiotics in footbaths to control digital dermatitis, or the use of oral antibiotics for calves, employs a huge amount of antimicrobials in mg/PCU. Targeted improvements in management or alternative therapies represent genuine alternatives that may drastically reduce antimicrobial use in these herds.
Injectable antibiotics represent the majority of use when recorded as sales by mass. Therefore, vets have a key role to play in reducing antimicrobial use by working with farmers to minimise incidence of disease. The majority of disease in dairy cattle takes place within the transition period, so strategies to monitor and reduce disease incidence during this time represents a key target to reduce injectable antibiotic use (Panel 3).
The vet’s role in change for the benefit of the health and welfare of cattle, as well as for economic and wider social benefit, is diverse, but inextricably linked to developing strong, professional relationships and understanding what motivates different clients.
Vets must not only engage in driving change with their individual farms – while understanding the bigger picture national strategies aim to achieve – but also horizon scan for new opportunities to ensure we continue to provide a service that is valued by clients and contributes to a secure and stable dairy industry in the UK.
Latest news
