Researchers: The risk of infection for livestock kept outdoors is often overlooked

More and more people want livestock to be allowed outdoors and to live more naturally. But when animals are moved out of the barn, the risk of infection also changes.

Researchers have examined how well disease prevention is adapted for livestock kept outdoors in a number of European countries, including Norway.

They found that current infection-control measures have largely been developed for animals housed indoors. As a result, important risk factors associated with grazing animals and outdoor access may be overlooked.

Researchers identified major gaps

The study also included countries outside the EU with comparable outdoor livestock production systems.

The researchers note that this is about biosecurity for the animals. The term covers all measures intended to prevent diseases and infections from spreading between animals.

The researchers reviewed 71 scientific studies that assessed biosecurity on farms with outdoor pigs, cattle, sheep, and other ruminants.

The aim was to identify which elements and measures are actually included when biosecurity is assessed.

The review showed that certain measures designed to prevent disease are almost always included. These include fencing, visitor controls, quarantine and testing of new animals, and the safe handling of dead animals.

The researchers also found that biosecurity assessments tend to focus more on how diseases enter a herd than how they spread within it.

Measures for animals that are kept outdoors or have access to outdoor areas are also often overlooked.

Pastures are a blind spot

Fewer than one in ten studies assessed biosecurity measures directly related to soil, pastures, and other outdoor environments. The use of vehicles in outdoor areas was also rarely examined.

“This is surprising, as much of the interaction between animals, people, equipment, and the environment take place outdoors in these production systems. Pastures and outdoor areas can play an important role in the survival and spread of infectious agents,” says Siv Meling

She is a researcher in livestock and wildlife health at the Norwegian Veterinary Institute and is an expert in biosecurity. She was one of the researchers involved in the research project European Partnership on Animal Health and Welfare.

Little focus on wild animals

Another important finding was that contact between livestock and wildlife often receives limited consideration.

Wild boar can spread African swine fever. Deer and badgers can contribute to the spread of bovine tuberculosis. Birds can carry a range of infectious agents.

Nevertheless, the review found that most issues relating to contact with wildlife were assessed in fewer than 30 per cent of the studies.

“This can be problematic because animals with outdoor access are often more likely to come into contact with wildlife than animals kept indoors,” says Meling.

Difficult to compare studies

The study also revealed considerable variation in the methods used to assess biosecurity measures.

Some assessments were designed to identify risk factors for specific infectious agents, while others focused on the farm's overall biosecurity.

When the objective was to investigate a single disease, certain biosecurity elements were far more likely to be omitted.

Meling says this makes it difficult to compare results across studies, production systems, and countries.

Important for animals, farmers, and authorities alike

What the researchers found has implications far beyond the research community.

If biosecurity assessments fail to capture key risk factors in outdoor production systems, producers, veterinarians, and authorities may all underestimate important routes of disease transmission.

At the same time, the researchers emphasise that keeping animals outdoors provides many benefits. Animals have greater opportunities to engage in natural behaviours, enjoy increased freedom of movement, and experience a more stimulating environment.

The objective is therefore not to move animals indoors, but to develop biosecurity protocols that better suit the challenges associated with outdoor farming systems.

Need tailored biosecurity

The study highlights a clear need to rethink biosecurity in livestock systems that provide access to outdoor areas.

Today's assessments often focus on housing facilities, fencing, and visitor controls, while less emphasis is placed on the conditions on pastures, the use of outdoor spaces, and contact with wildlife.

The researchers believe that pastures and the environment surrounding livestock deserve far greater attention than they receive today.

This would strengthen both animal health and preparedness for future disease outbreaks.

Reference:

Martin-Valls et al. Review of biosecurity parameters included in assessments of pig and ruminant farming systems with outdoor access, Preventive Veterinary Medicine: Regional Studies and Reports, 2026. DOI: 10.1016/j.pvmrsr.2026.100026

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