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Draw the Line on Livestock Diseases

Samantha ShieldsAnimal Health, Livestock diseases, Sanitation, Traffic Control Leave a Comment

A line of separation is a biosecurity practice that involves setting up boundaries or zones on a livestock operation. The purpose of the line is to block the introduction, or limit the spread of disease-causing agents (NPPC, 2013). Compliance with procedures for crossing the line can become an issue with farm workers and visitors. The line is meant to separate the “clean” from the “dirty”. Clothing, equipment, vehicles, etc. that could be carrying manure from another farm, field dirt or animal blood must be removed or decontaminated before crossing over to the clean side of the line, were livestock are housed. The line is an important addition for farm biosecurity protection, but it can represent a time-consuming process that almost invites short cuts and fibbing.

Separation is Worth It

For example, a tool needed to repair a tractor is located on the clean side of a line of separation, and a quick crossing over the line and back while wearing dirty overalls and manure-covered work boots shouldn’t cause any problems. However, a few clods of manure and dirt from the work boots fall off on the clean side of the line. Then, the manure is tracked into the livestock barn and unknowingly gets mixed in with the evening feed ration. An animal eats the ration and soon after shows signs of illness.

Keeping livestock healthy should be a top priority for producers. A line of separation is one of several methods for protecting animal health, by restricting access to livestock areas and requiring that steps be taken to lower the risks of infectious disease introductions. Regular biosecurity training for farm workers, putting up farm signs, and communicating instructions to visitors will make compliance with line procedures easier for everyone to follow.

Assess the Farm’s Traffic Flow

Every livestock operation, no matter what size, should develop a biosecurity plan that includes how lines of separation will be designated and managed. Begin your planning by looking at the flow of traffic on and off the farm, and where the high-risk areas are for livestock disease transmission. (Janni, 2015).

  1. Establish where the boundaries or biosecurity zones (restricted access, transition and controlled access) of the farm are.
  2. Assess the risk associated with each boundary zone.
  3. Choose which biosecurity protocols to use based on expected costs and benefits of managing the risks.

Put Boundary Zones on a Premises Map

Use an aerial map or schematic of the farm to create a premises map, and draw the zone boundaries. Think about who and what is crossing over these boundaries, how frequently and how much of a risk they pose for disease transmission. Some of these frequent visitors could include farm managers, employees, veterinarians, service providers and consultants. A veterinarian might pose a higher risk from working with animals on other farms. However, they are more likely to follow a farm’s biosecurity measures.

Vehicles and equipment traveling from farm to farm such as feed and milk haulers could be higher risks because the vehicles are difficult to decontaminate, and the drivers visit many other farms. It is important to assess each risk to find the best solution to prevent disease introductions to the farm.

Procedures for Crossing the Line

Once the risks are identified, strategies and procedures for managing the risks can be added to the biosecurity plan. The procedures for crossing a line of separation should be clear for everyone who enters the farm. An example of procedures for crossing a line of separation includes: (Janni, 2015):

  1. Enter through a biosecure entry.
  2. Remove and leave outer clothing and shoes on the dirty side.
  3. Disinfect hands.
  4. Step over the line of separation to clean side.
  5. Put on clean, barn-specific clothes and shoes.
  6. Enter production area.
  7. Reverse these steps to exit.

After the line of separation procedures are developed, the next step is to implement and communicate them to farm personnel and visitors. Placing signs around the farm will promote awareness among personnel and visitors. Breaks in the procedures can occur when people are not aware of the plan or do not realize why they need to follow the plan (Noll & Cardona, 2018).

Every farm has their own way of defining boundary zones and lines of separation. Identifying the flow, assessing the risks and communicating the procedures are the key for protecting your herd from infectious disease introductions.


Pork Checkoff. (2013). Establish a Line of Separation: Help Control the Spread of PEDV and Other Swine Diseases. [PDF].

Janni, K. (2015). Prevention- Biosecurity Training, Plans and Execution. [PDF]

Noll S, Cardona C. (2018). Rethink biosecurity. Retrieved from


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About the Author

Samantha Shields

Samantha Shields was an undergraduate student at the University of Vermont, studying for a Bachelor of Science in Biological Science, and a minor in Animal Science. She worked with ADBCAP Director Julie M. Smith, DVM, PhD, as an online outreach assistant intern. Samantha assisted with content development for the Healthy Farms Healthy Agriculture website by evaluating, summarizing, and presenting information about protecting animal health. At the University of Vermont, she was an active member of many programs including RALLYTHON, University of Vermont Program Board, Campus Recreation, and the Women’s Club Hockey. Samantha is interested in pursuing the field of epidemiology after graduation. She has a particular interest in the research of different factors that result in diseases, as well as public health emergency planning and response.

About the Editor

Joanna Cummings

Joanna Cummings received a Bachelor of Science in Horticulture from The Pennsylvania State University (PSU), with a specialization in vegetable crop and greenhouse production. At PSU, she was a research technician on no-tillage vegetable crop experiments, and a greenhouse assistant in the All-American Selections Research Gardens. Her career in the agriculture industry includes field research, work with dairy and vegetable farms, and as a greenhouse manager, estate gardener, landscaper and market garden entrepreneur. She transitioned to the science communication field after receiving a master of science degree in environmental communications from Antioch University New England. At Antioch, Joanna was a field botany laboratory teaching assistant, manager of the herbarium, and editor of the department's student newsletter, Notes and Niches. She currently works with Research Professor Julie M. Smith as a communications professional in the University of Vermont Animal and Veterinary Sciences Department. She is the webmaster for the Healthy Farms Healthy Agriculture website.

About the Editor

Dr. Julie Smith

Dr. Julie Smith is a research professor at the University of Vermont. Julie received her B.S. in biological sciences, D.V.M., and Ph.D. in animal nutrition at Cornell University. Since 2002, she has applied her veterinary background to programs in the areas of herd health, calf and heifer management, and agricultural emergency management. She has taught courses in animal welfare, calf biology and management, and ABCs of biosecurity to undergraduates, mostly in the Department of Animal and Veterinary Sciences. As a veterinarian and spouse of a dairy farmer, Julie is well aware of the animal health and well-being concerns of dairy animals. Julie has conducted trainings for Extension educators, livestock producers, and community members on the risks posed by a range of animal diseases, whether they already exist in the United States, exist outside of the United States, or pose a risk to both animal and human health. In all cases, she emphasizes the importance of awareness and prevention. In addition, she has led a number of projects on biosecurity and emergency disease preparedness.


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