Biosecurity - protecting the herd

Disease outbreaks on dairy farms can be devastating to both animal welfare and farm profitability, with losses in terms of reduced output, increased replacement costs, veterinary costs and labor requirements. Dairy farmers are becoming more aware of how biosecurity programs can help them prevent, or reduce the risk of disease entering and spreading in their herd. However, studies show that there are still only few that implement and strictly follow a biosecurity program on their farm.

Animal diseases lead to substantial losses for the dairy farms around the world. According to a British study contagious mastitis infections cost approximately $50 (£30, 37€) per cow/year, a case of digital dermatitis approximately $70 (£54, €67) per cow, and BVD (Bovine Viral Diarrhea) $100 (£63, 78€) per cow/year. A Swedish study showed that the yearly avoidable cost of mastitis in a 150-cow herd, assuming that the initial incidence of clinical and sub-clinical mastitis could be reduced by 50%, was estimated at $10 345 (£6 550, €8 095). Expressed as an average per cow/year, the avoidable cost of mastitis was estimated at $69 (£44, €54). There are ways to systematically reduce the risk of disease on farm.

The systematic approach

Preventing infectious diseases from entering and spreading on the farm requires a set of specific management practices, a biosecurity system, that protects people, animals, and ecological systems against disease and other biological threats. It is founded on three pillars: sanitation, isolation and traffic control.

These practices don’t need to be expensive; many of them simply require a management change. Seldom are large capital investments required, but everyone working on the farm must be involved. Neither do biosecurity programs have to be complex; they are in fact more proficient if they are not. What is important is that they are understood by all, and easily implemented.

Prevention always better than cure

By controlling the health of the animals and their movement the risk of having diseases introduced on the farm is reduced. A closed herd with its own replacement is the highest level of control. As soon as a new animal is introduced to the herd, the risk of contamination rises. This risk can be minimized with a system of biosecurity practices in place through isolation of new arrivals and disease testing of the new animals. In fact, regular testing of all animals has proven to be an efficient way to maintain good herd health. Reducing the diseases entering a dairy farm means less time is spent treating the diseases, drug and vet costs are reduced, and herd productivity is not compromised.

Not only do we need to control the cows. Good practices for people on the farm also need to be in place, with strict rules for visitors and their vehicles and good hygiene at all levels.

Pests such as rodents and flies can carry infectious agents, and even a small population of rats or mice can severely contaminate feed supplies. There are several solutions and practices that can be used for pest control.

Management routines to prevent spreading diseases

To prevent diseases from spreading in the barn, management of groups and housing is an effective strategy. Infected animals are kept isolated from the uninfected; and young cows are separated from the older. Sanitation is also important, everything on the farm needs to be kept as clean as possible; equipment, environment, clothing etc. Mechanical cleaning and the use of disinfectants will help in reducing pathogen levels. To reduce the risk of disease spreading between cows, a good manure management system needs to be in place, with adequate removal and storage. A simple routine of using separate loaders for manure and for feed can reduce the risk of contamination considerably.

If biosecurity programs reduce the risk of disease outbreak and subsequent losses - why are they not more widely used?

It has been shown in the Netherlands that closed herds operating with effective biosecurity systems had a 5% increase in net return when compared to herds where breeding replacements were purchased.1 Not all farms have the possibility to raise their own replacements, making the purchase of animals necessary. Biosecurity practices would help to protect their herd. However, several recent reports demonstrate the vulnerability of dairy farms as a result of the lack of biosecurity applied to cattle purchase.

One study from Iowa and Wisconsin in the US, showed that most herds that were increasing herd numbers did not operate a biosecurity system. As a result losses from both BVD and digital dermatitis were significant.2 Similarly a Canadian study identified a general biosecurity failing when purchasing replacement heifers, and such herds were more likely to be infected with Johne’s disease.3 In Wisconsin, it was found that less than half of the respondents to a producer survey actually tested their purchased cattle for diseases and less than half inquired about the herd of origin with regards to disease.4 Only about 20% of Idaho producers with herds undergoing expansion required any testing of purchased cattle for diseases other than mastitis.5

Just the act of looking at cattle more closely before purchasing could identify important diseases that could cause animal losses and economic damage to the farm. Pre-purchase testing can identify readily transmissible diseases in carrier animals. Improving the overall biosecurity on dairy farms could not only help prevent transmission of endemic diseases of economic importance, but also foreign animal diseases, such as Foot and Mouth Disease.

It has been shown that in many cases farms have not allocated space to isolate animals for the recommended three weeks before herd entry, and some producers choose not to test incoming animals because of the perceived costs. A British study suggests that the reason why biosecurity practices are carried out infrequently or not at all can be due to factors such as cost (in time and money), lack of proven efficiency of practices and a general lack of knowledge about biosecurity.

Not ‘one size fits all’

Depending on the animal disease in question, dairy producers may have several ways to reduce the risk of the disease impacting their herd. Which strategy to use will depend on several factors and there is no ‘one recipe’ that will fit all farms. The cost of implementing a strategy will also differ by farm and the disease being considered. Producers should work with their veterinarians to evaluate which biosecurity practices are most appropriate for their farm and then take primary responsibility for enforcing it on their operation.


1 van Schaik, G., A. A. Dijkhuizen, et al. (1998)

2 Faust et al., 2001

3 Chi, VanLeeuwen et al. 2002

4 Hoe and Ruegg 2006

5 Dalton et al., 2005

Read more:

Biosecurity principles as applied to udder health

Develop strategies and standards to prevent introducing intramammary infections into a herd

Economic Impact of Mastitis in Dairy Cows

The potential losses associated with herd infection with BVD and Johne’s Disease and an estimate of the cost of measures to prevent herd infection for Irish Dairy Farms

An Evaluation of Dairy Producer Emergency Preparedness and Farm Security Education

Dairy herd biosecurity

DeLaval biosecurity guide - Health protection and sanitation strategies for dairy farms

Guarding Against the ‘Trojan Horse’: Practical Biosecurity Measures for Dairy Farms

Biosecurity costs explained

Biosecurity on Cattle Farms: A Study in North-West England

Biosecurity can save dollars

Dairy disease prevention assessment tool


Monica Wadsworth

Monica Wadsworth
85 articles

Writer at

Read more »

Preventing infectious diseases from entering and spreading on the farm requires a set of specific management practices, a biosecurity system, that protects people, animals, and ecological systems against disease and other biological threats. It is founded on three pillars: sanitation, isolation and traffic control.