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Farm animal practice
Role of the veterinary surgeon in managing the impact of dairy farming on the environment
  1. Martin Green,
  2. James Husband,
  3. Jon Huxley and
  4. Jonathan Statham


With increasing concerns surrounding the causes and consequences of climate change, the impact of agriculture on the environment has come under intense scrutiny. For example, it is claimed that the livestock sector produces 18 per cent of all worldwide greenhouse gas emissions (measured in carbon dioxide equivalents), which, on a global basis, equates to more than all means of transport. It is therefore important to consider changes to farming systems and management methods that could reduce negative environmental effects. It is likely that pressure will mount on agriculture to proportionally reduce its emissions in line with other industries in order to meet government targets on greenhouse gas emissions. However, controversy remains over which farming methods result in the best environmental outcomes and there are also potential areas of conflict between environmental issues and animal health/welfare considerations or perceptions. This article considers the role of the veterinary surgeon in mitigating some of the potentially harmful effects of dairy farming on the environment.

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Martin Green graduated from Bristol in 1987. He has spent over 10 years in farm practice and a further 10 years combining clinical practice with dairy cow research. He is currently professor of cattle health and epidemiology at Nottingham. He holds RCVS and European diplomas in cattle health and production, and is also an RCVS specialist in this subject.

James Husband graduated from Cambridge in 1993 and spent five years in mixed practice in Glastonbury, after which he took up a two-year residency at Bristol. He subsequently moved to Gloucestershire, where he worked in cattle practice. He is now a co-director of Evidence Based Veterinary Consultancy (EBVC) and a special lecturer at Nottingham. He holds the RCVS diploma in cattle health and production, and is also an RCVS specialist in this subject.

Jon Huxley graduated from the Royal Veterinary College in 1995. He is currently associate professor of farm animal production medicine at Nottingham. He holds the RCVS diploma in cattle health and production and the European diploma in bovine health management.

Jonathan Statham graduated from Cambridge in 1996. He is a partner in Bishopton Veterinary Group, a 19-vet practice in Yorkshire and a member of XLVets, and a director of RAFT Solutions. He is chair of the British Cattle Veterinary Association (BCVA) Herd Health Management and Endemic Disease Group, and is a member of the Cattle Health and Welfare Group (CHAWG). He holds the RCVS certificate in cattle health and production.

How do dairy cows impact their environment?

As is the case with many industries, dairy farming can influence its environment in a variety of ways. The main issues are generally categorised as those associated with soil, water, air, energy usage and biodiversity. While a detailed description of each of these areas is beyond the scope of this article, major environmental concerns are outlined in Table 1. Water pollution from nitrogen compounds is considered to be a particular issue (Box 1).

Table 1

Areas of the environment that are potentially harmed by dairy farming

Box 1: Nitrogen vulnerable zones

An EU Nitrates Directive was adopted to reduce water pollution caused by nitrogen from agricultural sources. This Directive requires Member States to:

  • Designate all land draining to waters that are affected by nitrate pollution as nitrate vulnerable zones (NVZs);

  • Establish a voluntary code of good agricultural practice to be followed by all farmers throughout the country;

  • Establish a mandatory ‘action programme’ of measures for the purposes of tackling nitrate loss from agriculture;

  • Review the extent of their NVZs and the effectiveness of their action programmes at least every four years and to make amendments if necessary.

A map of current NVZs can be viewed at See further information for guidance on how to manage land in NVZs.

Whole farm evaluations

Difficulties with a whole farm assessment

Quantitatively evaluating all components of a dairy business that have an environmental impact is not trivial. Such a scoring system would need to include beneficial and detrimental effects of all aspects of the farm and include items beyond farm sales (ie, the pathways of products brought onto and taken off farm). The weighting of different components that affect the environment is not clear cut and neither are the ‘environmental opportunity costs’ of changing to different systems. For example, if improved biodiversity is at the expense of increased greenhouse gas emissions, which is more valuable in an environmental context?

Carbon footprinting

One method currently being piloted is that of whole-farm ‘carbon footprinting’. This involves examining data from all aspects of the farming enterprise that produce methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2), and calculating the total CO2 equivalents per litre of 4 per cent butterfat-corrected milk produced. There are several ways to break this down but the main categories and subcategories are:

  • Livestock. Purchased feed, bedding, enteric fermentation, manure management, purchase/contract rearing;

  • Cropping. Fertiliser manufacture and spreading, manure spreading;

  • Fuel and energy use.

Quantitative models take a relative weighting of these different categories into account. For instance, artificial fertiliser production carries a high environmental cost due to the quantity used on farm and also the quantity of N2O produced in its manufacture.

Evaluating the whole business allows farmers to identify and improve the major environmental issues arising from their dairy business. Many environmental improvements can be made that have associated financial benefits. Methods to reduce potentially deleterious environmental impacts are described later, but some common areas that also lead to significant financial savings are:

  • Improved health and reproductive performance (eg, for each day that a calving interval is extended, there is an estimated increase of 18 kg of CO2 produced per cow per day);

  • Segregating roof water for washing down parlour standings;

  • Using plate coolers to cool milk (Fig 1);

  • Testing nutrient value of manures and producing a nutrient plan matched to slurry analysis;

  • Using direct slurry injection to reduce nitrogen losses and anaerobic spoilage;

  • Using fuel efficient tractors;

  • Avoiding overmixing of total mixed rations.

Fig 1

Energy saving changes to lighting, machinery and dairy equipment are effective ways of reducing farm energy use. For example, precooling of milk using a plate cooler substantially reduces the energy requirements of refrigeration

It is worth noting that, periodically, considerable grants become available to help finance investments that contribute to improvements in areas of environmental concern. The availability of these grants and initiatives is likely to increase over the coming decades, when the current pressure on government spending eases.

How can environmental impact be reduced?

A number of methods can reduce the impact of dairy farming on the environment (Table 2).

Table 2

Suggested methods for reducing the environmental impact of dairy farming

Fig 2

Compacting manure and covering slurry stores or manure heaps reduces ammonia and nitrous oxide emissions

Fig 3

Carefully balanced diets improve performance and reduce inputs and waste per litre of milk produced

Dietary manipulation is an interesting area and one that demonstrates some of the difficulties and anomalies that exist when considering the environment. For instance, feeding more starch and less fibre to a dairy cow will mean relatively more propionate, and less acetate and butyrate produced in the rumen, which leads to less methane production. A herd producing 8000 litres of milk per annum that has a relatively high starch content in the diet will have lower methane production per litre (assuming an equivalent feed rate) than a herd producing the same milk and being fed lower starch content and higher digestible fibre in the diet. However, such starch-based diets have the potential to cause acidosis, which can have subsequent deleterious effects on cow health and welfare. This is an example of a potential conflict between environmental and cow considerations – feeding a high starch diet may be useful in reducing methane production and the environmental impact of dairying, but it could result in poorer cow health or increase production costs, so which factor is the more important?

Another example of a conflict of interests is the use of palm oils in dairy cow diets. This represents a human, economic and environmental dilemma, where milk price in some purchasing contracts depends on the percentage of butterfat in milk, which can sometimes be cost-effectively boosted using palm oils (C16 fatty acids). The production of palm oil is generally considered to be severely detrimental to the environment, although it can also provide an income for some of the world's poorest societies. There are clear ethical difficulties in making decisions in which conflicts exist between environmental, animal, economic and human requirements, but such dilemmas have to be faced.

In the future, certain feed additives may be able to influence the impact of dairy cows on the environment by instituting potential methane-reducing effects. These include:

  • Ionophores, such as monensin, although this is banned in the EU;

  • Some unsaturated oils, such as linseed, and some essential oils, such as extracts from horseradish and garlic, but more research is required in this area.

Efficient milk production to reduce environmental impact of dairy farming

For all dairy farming systems, in all countries, improved efficiency of milk production will have an impact on reducing the negative environmental effects of dairy farming (Fig 4). For example, for any particular system, if fewer cows (and replacements) are required and there are fewer ‘lost’ litres of milk, the environmental impacts per litre of milk sold or per animal on the unit will be reduced. ‘Lost’ milk here includes milk that does not enter the food chain following animal treatment or a reduction in yield that occurs following clinical or subclinical disease or poor reproductive performance.

Fig 4

Efficient milk production from healthy cows is an important step in reducing the environmental impact of dairy farming

A reduction in greenhouse gases, and the use of non-renewable resources and chemicals per litre of saleable milk is an inevitable consequence of improved health and fertility, because fewer cows at a given level of production are required to produce the same quantity of milk. The difference in environmental impact between the best and poorest performing herds in terms of health and fertility is likely to be very large. With regard to fertility alone, reductions in methane emissions of the order of 25 per cent appear to be possible between the best and poorest herds.

Improving health and fertility to reduce the environmental impact of dairying has the substantial advantage that it also beneficial for cow welfare and farm financial returns – in this respect, it is potentially a ‘win-win’ situation. This is clearly an area in which the veterinary profession can and should take a leading role.

Improving health and reproductive performance

The general consensus is that there is vast room for improvement in the health and reproductive performance of many dairy units in the UK (and internationally). Key conditions, such as mastitis, lameness, metabolic disease, infectious disease and periparturient problems, remain all too prevalent and, for the most part, there is no national structure to tackle endemic disease. For example, recent data indicates that, on a national basis, clinical and subclinical mastitis has improved little over the past decade and neither has cow lameness. Reproductive performance has declined significantly over the past 15 years. Milk recording data suggest that about 25 per cent of herds cull more than 30 per cent of cows per year, with the most common reasons for culling being infertility, mastitis, lameness and calving-related issues. However, many diseases are difficult to quantify on a national basis because of a lack of available national data, a situation that gives the industry little credit.

Despite general agreement that dairy cow health could and should be better, and that improvements would result in important environmental benefits in addition to welfare improvements and financial returns, the undertaking of regular detailed herd health and preventive medicine on dairy units remains relatively uncommon. While many herds have routine reproductive visits and infrequent (often annual) evaluation of a ‘health plan’, regular (fortnightly or monthly) evaluation of all aspects of health and production is the exception rather than the rule. This raises the question: why is proactive preventive herd health and production management (HHPM) (or active health planning as opposed to the production of an annual health plan) not more common throughout the dairy sector?

Role of the vet

HHPM works best with the vet acting as a coordinator to link cow health with other inter-related aspects of dairy farming (Box 2). HHPM has a central role in the management of milk production. The process is best described as an interactive, dynamic procedure that balances environmental, animal health/welfare and safety/sustainability of food production on a daily/weekly basis.

Box 2: Role of herd health and production management

The veterinary profession is positioned as an ideal ‘custodian’ to manage this process. For example, production efficiency, feed management (including the use of byproducts), social/economic factors, improved fertility, food security, animal health/welfare, consumer awareness/marketing and sustainable production are all areas that the vet can be involved with and help to form a cohesive farm policy. It is apparent that many farm advisers will quickly take on these roles if vets choose not to.

The benefits of active HHPM have been identified in research and also by some vets and farmers who see the gains to be made. The reasons for farms not being involved with routine HHPM seem to include a perceived lack of benefit to the farm (financial or otherwise), insufficient income (milk price) to allow the necessary capital investments when required, lack of knowledge or incentive from the attending veterinary surgeon (whether time or income-based) or a lack of communication between stakeholders in terms of what can be achieved.

HHPM is an active process that includes monitoring of early warning indicators, weekly/monthly appraisal of major farm health, fertility, production and financial parameters as well as a regular overview of all preventive systems. Holistic HHPM requires detailed knowledge of the farm, excellent record keeping and analysis and a focused team approach with outstanding communication. Such health management can be tailored to dairy units of any size. The objective of HHPM is to optimise cow health and welfare as well as farm sustainability and profitability. HHPM is not a one-off ‘herd visit’ to solve a herd problem or the infrequent production of a herd list (‘health plan’) of preventive measures.

Specific areas within HHPM that require veterinary involvement are discussed below.

Farm data

High quality farm records and data management are absolutely essential, especially as many management decisions will be driven by their interpretation. The vet has a crucial role to play in assessing data quality, suggesting improvements and encouraging accurate use.

Data monitoring – early warning systems

Routine assessment of records and early indicators that health or production are not on target are central to HHPM. The veterinary surgeon can take responsibility for this phase and thus ensure the unit remains on an even keel where possible. Realistic targets need to be set for individual units, with the agreement of owners and herdspersons, and will depend on farm facilities and staff capability. The vet is in an excellent position to offer perspective on a unit's performance and to suggest interference levels for health and production indicators.

For data monitoring to be effective as an early warning system, it is important that the indicators measured are meaningful in the short term. Therefore, monthly or three-monthly rolling average incidence rates or prevalence estimates are useful. A balance has to be struck between examining too many parameters (and hence making things unnecessarily complicated) and choosing too few whereby important factors affecting welfare, sustainability and profitability are omitted. However, with appropriate computer systems in place, regular examination of a variety of indicators becomes much easier.

Action and reassessment

When targets are not being met, a decision has to be made as to when and how to intervene. The vet requires specific skills in the diverse areas of health and production but not all issues will be central to his/her areas of skill. In such cases, the vet is the ideal person to encourage conjoined advice. For example, if expertise in feeding, housing or financial matters is outside that of the vet, collaboration can be sought. However, the vet is well placed to coordinate that advice and keep a perspective on cow health. Practitioners are present regularly on the unit and therefore are able to assess the implementation of any changes. A crucial aspect of managing change is encouraging staff and instilling a positive team approach. Expectations need to be realistic and it needs to be understood that improving health and/or production is an iterative process – the perfect solution may not be found immediately and further changes may be needed to achieve the required effect.

A potential difficulty with health intervention can be convincing owners or staff that extra resources (time or money) are worth investing in a given area. In such cases, it can be worth forming some simple farm scenarios or models to illustrate particular points. Another aspect of health intervention may include the need for farmer training. Veterinary surgeons can advise on this and can also help to formulate farm protocols where necessary. The results of training programmes and new protocols can subsequently be monitored in terms of herd performance.

The future?

There are likely to be a number of varied and taxing challenges for both animal and plant agriculture in the UK and worldwide over the coming decades (Table 3). These challenges will undoubtedly create complex and conflicting demands. What may happen in the future in terms of dairy cows and the environment is far from clear and is bound to be politically driven. Some areas where change should occur are:

  • Development of a better holistic understanding of the true environmental impact of different dairy farming methods and systems;

  • Alteration of some farming methods to be acceptable to modern society in terms of environment and welfare;

  • Discussion and progress in areas where there is conflict between cow welfare and the environment;

  • Inclusion and progression of the veterinary profession so that it delivers an evidence-based, coordinated approach to cow health and reproduction on a national basis;

  • Accurate measurement of important diseases on a national basis;

  • Relevant research on how to reduce the environmental impact of livestock farming.

Table 3

Future challenges for the agricultural sector

It is clear that the environmental impacts of livestock farming are now well recognised. While it is important that agriculture deflects unnecessary scaremongering, it is also important that steps are taken to develop and introduce measures that will lead to sustained improvements in environmental impacts in the long term. The veterinary profession has the opportunity to be central to this process.

Self-assessment test: Role of the veterinary surgeon in managing the impact of dairy farming on the environment

  1. What are the main greenhouse gas emissions associated with dairy farming?

  2. Why is the veterinary role in active herd health and preventive medicine likely to be beneficial for the environment?


  1. Methane, nitrous oxide, ammonia and carbon dioxide

  2. Because it should result in a reduced environmental impact (eg, lower greenhouse gases and energy usage) per litre of saleable milk from the unit (as fewer cows will be culled and there will be reduced losses in milk production and discarded milk)

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