Herd health advice on preventive medicine

It is often said prevention is better than cure and this cannot be over emphasised when discussing dairy herd health.

From a purely economic point of view, pre-emptive steps to control disease outbreaks cost clients far less than treating problems that arise later on. From a veterinary perspective, this type of proactive care also ensures healthy herds and establishes long-term client relationships with the vet.

Preventive medicine is fundamental to increasing farm profits and sustainability, and focuses the vet-farmer relationship on to improving performance. Attitudes to farm veterinary care have changed over the past few decades and demand for preventive health care is increasing.

This article aims to provide an introduction to the “five pillars” of preventive medicine: diagnostics, biosecurity, nutrition, environment and education. Examples of commonly encountered scenarios in large animal practice will serve to highlight the significance of preventive medicine.

Health planning

Health planning is a key mechanism for putting preventive medicine into practice. Often regarded as a box ticking exercise, health plans need to be living documents and an integral part of farm management.

A health plan should be modelled to be farm-specific, highlighting the most problematic diseases and thereby directing efforts to their control or eradication. It relies on making efficient use of technology to analyse production data thoroughly and can flag up issues to be managed accordingly.

As stock numbers increase and production costs rise, “fire brigade” work is called on less and routine treatment protocols are now common on dairy units. Health planning is focused on identifying risks and applying controls, but requires a synergistic relationship between the farmer and vet to recognise these problems and agree on a plan going forward.

Prioritisation of new changes is important, in combination with realistic projections regarding a farm’s targets for the coming year. For example, due to the complexity of Johne’s disease blood testing, once prevalent it can take years to eradicate.

Costings

Knowing the costs of diseases on the farm and their components allows for a judgement to be made about whether allocating resources for improvement will result in profit. The costs associated with any disease can always be divided into direct and indirect costs.

Direct costs include veterinary treatment, farm labour, discarded milk and overall reduced yield. Indirect costs are more difficult to calculate and include the impact on fertility, culling rates and risk of other diseases.

Due to the complex inter-relationships of some diseases – in particular, fresh cow diseases – it can be difficult to quantify these and the literature reflects this, with varied cost estimations for the same disease. Ketosis has been shown to decrease milk yield two to four weeks before diagnosis and continues for a varied length after diagnosis, with one study losing approximately 350kg of milk per case (Schultz et al, 1999).

Calving to conception has been shown to be increased by 16 days (Walsh et al, 2007) and the risk of developing a left displacement of the abomasum increases by 2.6 times (Duffield et al, 2009). With simple management practices, cases like these can be reduced and lessen the overall risk of periparturient diseases.

Diagnostics

With appropriate diagnostics, we can determine prevailing farm pathogens and use this to inform protocols in the health plan – in particular, vaccinations – as well as antimicrobial and anthelmintic treatments. Disease status on a farm will also influence quarantine protocols for newly purchased stock.

Disease testing should always be a priority for on-farm discussion and regular blood sampling of dairy youngstock – for example, bovine viral diarrhoea (BVD) – should be actively encouraged to assess status, as well as monitor the progress of disease control strategies.

Sampling youngstock older than approximately eight months of age ensures maternal antibody has waned and any positive results will indicate recent exposure within the herd.

Vaccination is the most common example of preventive medicine; however, it must be integrated into a control plan and not be regarded as the only method of disease control. Using calf pneumonia as an example, management and environmental factors play such a crucial role in the disease process and must also be improved for a vaccination plan to be successful.

Due to the significant financial commitment vaccinating large herds represents, the vaccination policy must suit the needs of the farm. On one hand, vaccination severely mitigates the likelihood of a specific disease outbreak; on the other, vaccination can be costly for farmers who may never see an instance of the disease.

It is dependent on weighing up risk of disease and treating an outbreak, versus the cost of vaccination – and, if disease-free, deciding whether good biosecurity alone is enough to maintain this status. Discussing the use of vaccinations on a dairy farm is beyond the remit of this article, but Table 1 describes a standard dairy protocol.

Biosecurity

Biosecurity can simply be defined as the risk of disease entering the herd. It involves the identification of risks to animal health and welfare, and mitigates those risks through best management practices, using basic knowledge of disease epidemiology. For example, infectious bovine rhinotracheitis (IBR) is highly transmissible and, therefore, contact with neighbouring cattle is a significant risk for disease transmission.

Conversely, people and indirect contact play a significant role in BVD and bovine TB transmission (Sibley, 2010). The importance of biosecurity on farms can be easily overlooked and yet implementing simple precautions can be critical to preventing disease outbreaks. It is imperative protocols we create as vets are logical and easy to understand, and these should be explained clearly to all those involved with the health and welfare of the animals.

Purchased stock are the biggest disease threat to a herd (Van Winden, 2005) and a quarantine procedure with a minimum of 21 days should be adhered to. Cattle should be sourced from an accredited herd or blood-tested before moving, particularly for Johne’s disease, BVD and IBR.

It is not always necessary to purchase from accredited free herds, but knowing disease status enables risks to be managed appropriately for that farm (Sibley, 2010). Panel 1 illustrates key areas to investigate when analysing biosecurity on farm.

Nutrition

Postpartum diseases in fresh cows are readily related to poor transition cow management, often resulting from poor intakes in early lactation and inappropriate body condition greater than three at dry off.

Strategic nutritional scoring is a key factor in preventive medicine to allow for important management changes. Body condition scoring, rumen fills and beta-hydroxybutyrate monitoring can target crucial stages in production and allow for interventions before a new lactation.

Overconditioned cows at calving will struggle to meet high feed intakes to match the energy demands in early lactation and are much more susceptible to ketosis. Feeding cows sufficient fibre in the dry period will help promote intakes postpartum.

Monensin boluses can also be targeted at cows that may require additional aid in energy provision, but should be used selectively, in conjunction with on-farm monitoring.

Several factors may indicate a potential nutritional problem on a farm. Metabolic disease incidence rates of greater than 10% and extremes of body condition in greater than 10% of the herd can also be an indicator (Ishler et al, 2015).

Failure to achieve peak milk production and poor fertility can be indicators for nutritional analysis.

Environment

Optimising cow comfort is vital in high-yielding dairy herds to enable maximum production and, in particular, when dealing with lameness cases.

Environmental factors are often suboptimal and yet changes to them are frequently associated with large costs – for example, altering passageways and improving shed ventilation. Excessive time spent on concrete walking surfaces and poor lying times predispose high-yielding cows to claw horn lesions (Cook, 2006).

A poor environment in which lame cows struggle to maximise lying times often results in extended lame periods and delayed cure rates. A cow comfort index is measured as the proportion of cows in contact with a cubicle that are actually lying down. This should aim to be at least 85% at one to two hours post-milking.

Bach et al (2008) researched factors affecting productivity and found each hour of increased resting time resulted in a gain of 1.7kg of milk production. Taking an opportunity to walk around the farm after milking time and watch cows walking the passageways and cubicle usage can focus on areas for improvement, particularly if lameness is a concern.

Education

Farmer education and engagement is critical to fully implement preventive health plans on farm.

Once all farm staff understand the pathogenesis of common infectious diseases, it will be easier for them to recognise these problems on their own farm and fully appreciate the control measures to eliminate them.

It is imperative we as vets communicate this information clearly and concisely, and discuss these topics further with farmers at meetings. Continuity of veterinary advice is extremely important and detailed knowledge of the farm system must be understood before tackling disease management issues.

Summary

Preventive medicine consists of a range of measures taken for disease prevention and improving health status of the herd. Diseases can manifest in any farm environment and the key to success is understanding and eradicating these diseases before they occur.

By consultation and advice from the vet, and through education and eradication programmes, it is hoped some of the diseases highlighted in this article can one day be finally eradicated or, at the very least, become a far less frequent presence on the well-managed dairy farm.