Highlights: What You Need to Know About Biosecurity

  • Maintaining a truly closed herd and managing farm traffic are the most effective tools to prevent disease introduction. Current production models however frequently require herd expansion and off-site heifer raising in order to remain competitive.
  • The cost of disease introduction can vary greatly depending on the circumstances, with production, disease and death losses ranging from nominal to costs in the tens or even hundreds of thousands of dollars. Some outbreaks such as Tuberculosis or Hoof and Mouth Disease may result in the loss of the entire herd.
  • Given the differences in facilities, management practices and producer risk aversion, there is no one-size-fits-all dairy biosecurity program. Your veterinarian can assist in designing a program that works best for your dairy.
  • Great strides have been made reducing animal testing costs by using pooled samples. In addition the state veterinary diagnostic laboratory offers partially subsidized testing.
  • This article provides an overview of the basic components of dairy biosecurity and related economic implications. Readers are also directed to effective resources to assist producers in implementing a plan that’s right for your dairy.

 For a quick introduction to protecting your farm from disease introduction and even farm theft, click here for a fun video presentation by Dairyman Ted

CAUTIONARY TAILS: Real-life Biosecurity Train Wrecks on California Dairies

Like car or home insurance, it can be difficult to measure a return-on-investment for biosecurity efforts. If you’ve prevented an outbreak from occurring on your dairy, you really have no way of knowing what losses or costs you’ve avoided.

It can be instructive however to examine what happens when biosecurity fails…

  • Described as a “nearly” closed herd, the producer only purchased fair animals and bulls. Using only a single killed vaccine annually, there was inadequate protection when the Bovine Viral Diarrhea (BVD) virus was introduced, resulting in animals off feed, decreased milk production and profuse diarrhea in the lactating herd.
  • A shipment of fresh and late pregnant first calf heifers breaks with classic BVD approximately 7-14 days following arrival from Idaho. In this case, it was the new arrivals that became ill, likely from sub-clinically infected resident herd animals.
  • A dairy experiences an ongoing problem with first calf heifers breaking with diarrhea after freshening, a condition which did not respond to treatment. Testing demonstrated Johne’s Disease in the sick animals, all of which possessed USDA ear tags indicating they were purchased from another state.
  • Two herds each purchase a TB positive animal from a herd later found to have bovine tuberculosis. One herd was depopulated while the other went into long-term quarantine using testing and slaughter to eliminate the disease.
  • In order to limit feed expenses a calf ranch owner takes hospital milk from a dairy and feeds it to calves. The resulting Salmonella dublin outbreak resulted in calves dying at the rate of about 20 calves per day for a total of about 80 mortalities.


Because dairies vary enormously by facility, management and disease exposure, a biosecurity plan will be different for each dairy. In addition, as our understanding of disease transmission grows and as new tests and vaccines become available, the evolving issue of biosecurity continues to grow even more complex. Finally and most importantly, on any given dairy, investment in biosecurity will be driven by the producer’s own goals, perception of risk and personal risk aversion.

A wide variety of factors influence a producer’s biosecurity goals. Selection of which procedures are adapted will frequently be based on a producer’s own experience with livestock disease or outbreaks that have involved his neighbors. A producer’s practices relative to acquiring replacement heifers or cows will influence his sense of risk.

Cost is an inevitable a consideration. Testing returning replacement heifers raised off-site for Bovine Viral Diarrhea (BVD) may not be viewed as necessary or economical if an aggressive vaccine program is already in place. Replacement animals purchased from a sales barn however may be seen to merit more extensive testing for contagious mastitis pathogens.  External incentives may also play an important role in determining producer goals. Operations selling cattle, semen or embryos may have international trade requirements, such as testing for Bovine Leukosis Virus (BLV) or Bluetongue.

Clearly there is no “one-size-fits-all” biosecurity plan for dairies. A producer working with his veterinarian will tailor a disease prevention program to the situation on his own operation.

How Much Biosecurity Is Being Used on U.S. Dairies?

Given the high rate of vehicle, employee and animal traffic entering and leaving an average farm, the dairy industry may be the least bio-secure of all the major livestock commodities. Several academic and USDA surveys (Wells 2000, NAHMS studies 1996, 2002 & 2007) have reviewed biosecurity procedures utilized on U.S. dairies. While different surveys are not always in complete agreement, in general we can estimate that:

  • Roughly 40% of dairies introduce new animals every year.
  • Only about half of dairies importing new animals require their vaccination.
  • Approximately 3/4 of dairies use no pre-purchase testing.
  • Some 80 – 90% of dairies do not isolate new additions for observation.
  • 67% of California dairies don’t have new bulls checked for fertility or venereal disease.
  • About half of dairies do not follow label instructions for killed vaccines.
  • Some 1/5 of dairies use no vaccination in cows at all.
  • About 1/3 of dairies routinely use the same equipment to move manure and feed.


While implementing biosecurity practices on a dairy need not be always costly, developing a program none-the-less requires investment in the form of management planning and oversight, materials and employee time. Dairy producers understandably desire to know what economic benefits will be realized for their efforts.

Dairymen are frequently subjected to estimates of economic losses associated with particular diseases in the United States: $2 billion annually for mastitis, $250 million for Johne’s Disease, $16M for BLV and $350 M in production losses for BVD.  While important concepts, these figures have little relevance to producers trying to determine whether to invest resources in disease prevention procedures.

Perhaps more useful are descriptions of the economic impact of actual outbreaks. One such review for instance reported herd losses due to BVD introduction ranging from $2,600 to more than $100,000, depending on the size of the herd and the severity of the outbreak.

Also instructive are studies which model disease-specific losses and compare them to the estimated cost of control programs. A New Zealand study for instance modeling 300-cow dairies estimated that over 10 years a test-and-cull plus vaccination program was less expensive then living with endemic disease ($25,000 vs. $37,00 U.S.) and far cheaper than a BVD abortion outbreak ($93,000). Similarly, another study modeling 100-cow US herds with 50% BLV subclinical infection estimated  annual losses at approximately $6,400, compared with $1,700 for a test-and-control program.

Application of these return-on-investment studies to an individual dairy however may be limited. In order to model cost return for biosecurity measures taken, assumptions must be made including the disease prevalence in a region, virulence of a strain, likelihood of introduction, innate herd immunity and the mortality and production losses which would likely result. All of these variables may be profoundly different from one region to another or from one dairy to another. In fact, some surveys have suggested that this lack of specific risk & return economic data is one of the primary impediments to producer adaptation of biosecurity measures. With the herd’s veterinarian a producer can review the farm’s management practices in light of available prevalence information to help clarify the dairy’s goals.

Ultimately investment in biosecurity practices is probably best seen simply as another form of insurance. In order to get a picture of California producer’s testing practices and on the prevalence of common diseases facing them an excellent survey is available . 


Because of variability in operations and producer goals, a detailed description of what should be included in a biosecurity program is beyond the scope if this article. In general however a dairy biosecurity program will include:

Sourcing Animals – The single greatest threat of introducing disease comes from purchasing animals co-mingled from multiple sources, such as from a sales-barn. Knowing the disease and vaccination status from source herds is critical. Ideally your herd veterinarian should consult with the seller’s veterinarian prior to purchase.  Herd additions should be transported in a cleaned and disinfected trailer, ideally the producer’s own trailer.

Pre-purchase Examination & Testing – Because of the perceived cost, many producers won’t consider pre-purchase testing. Great strides however have been made with testing of pooled samples that can greatly limit costs. In order to assist monitoring and controlling livestock disease in the State, the California Animal Health and Food Safety Lab (CAHFS) also offers partially subsidized testing. Your veterinarian can assist you in selecting the most cost-effective pre-purchase testing options for replacement animals.

Pre-purchase examination can also yield important information. This can include a hoof trimmer’s examination of feet for heel warts and a veterinarian’s breeding soundness exam for replacement bulls. If pre-purchase examination and testing hasn’t already been completed by arrival at the new dairy, the isolation period can be used to complete the tasks.

Isolation of New Additions (“Quarantine”) – Sometimes referred to by producers as “quarantine” (which in reality has regulatory implications) isolation of new arrivals remains one of the most important biosecurity tools available to producers. This can be particularly true in limiting fast moving viral diseases like IBR and BVD. Experts frustratingly recommend variable isolation periods, ranging from 7 to 30 days, but your veterinarian can help establish a workable protocol for your dairy. Isolation is ideally performed on a site separate from the dairy, but it may also successfully be accomplished in a different barn or separate pen on your facility. The ultimate goal is for “quarantined” animals not to share the same air space, waterers, or feeders, or have nose-to-nose contact with resident cattle. If not already completed, animal testing can be performed during the isolation period. Lactating cattle whose milk cultures have not been reported out should be milked separately and/or last. Foot trimming and examination (and medicated foot bath treatment) may also be performed during isolation, as can breeding soundness examinations for newly purchased bulls.

Vaccination – While effective vaccines don’t exist for some important pathogens (Salmonella, Mycoplasma, Johne’s), vaccination still remains perhaps the cheapest, most cost-effective biosecurity tool available to producers. With more than 600 licensed food animal vaccines marketed in the U.S. however, producers will need to consult with their herd veterinarian to develop an effective and economic vaccine program. Careful attention should be given to maintaining cold-chain (refrigeration) of vaccines and making sure vaccine labels are followed. This is particularly important with killed vaccines which may require two initial doses in order to realize the full protection of the vaccine. The herd owner and veterinarian should review the vaccination plan annually.

Traffic & Perimeter Control– Involving constant attention and enforcement, managing routine traffic remains one of the most challenging aspects of dairy disease control. Veterinarians, hoof trimmers, feed trucks, dead haulers, equipment serviceman and even employees can introduce disease, making traffic control an essential component of a biosecurity plan. SOPs, traffic routes and parking should be established individually for each visitor. Signage for instance should direct intermittent visitors to a peripheral parking site. Mortality pick-up should be located so that the rendering truck does not contaminate the facility. When possible, feed delivery and service truck routes should not cross dairy equipment routes. Employees should arrive in clean attire or facilities made available for them to change into work clothes and boots used only on the dairy. Wildlife fencing and vermin control should be implemented as needed.


Maintaining a closed herd and managing visitor traffic are probably the two most effective methods to prevent disease introduction. Currently effective business models however frequently require herd expansion and/or off-site heifer raising in order to remain competitive. Both closed herds and herds which bring animals onto the dairy can benefit from implementing basic biosecurity precautions.

A dairy producer interested in implementing or expanding his operation’s biosecurity plan can choose one of several different paths, from implementing bare minimum practices  to conducting a herd risk assessment in order to optimize a program for the dairy. Below are some examples of the various types of biosecurity procedures that can be undertaken.

Absolute Bare-Minimum Practices – Risk-tolerant producers may choose not to perform pre-purchase testing, but can still employ four other strategies: (1) determine diseases present and the vaccine history of the herd of origin (2) carefully examine cattle, particularly cows for mastitic udders & feet lesions and breeding bulls for testicular abnormalities (3) isolate and monitor new arrivals as they become acclimated to the new facility and finally (4) never purchase cattle from a mixed origin source.

These minimal procedures should not be confused with an effective biosecurity program. These practices will not prevent entry of animals carrying subclinical disease. Combined with an aggressive herd vaccination program however, these procedures probably represent the lowest input cost for the most return in protection.

Simple, Effective, Generic Plan – Many producers will be interested in a simple list of biosecurity practices that should be followed on most dairies. One of the simplest, most concise guides explaining implementation of a basic dairy biosecurity program was developed by Dr. Dale Moore now at Washington State University, “Guarding Against the ‘Trojan Horse’: Practical Biosecurity Measures for Dairy Farms

Comprehensive Plan: Do a Risk Evaluation – Many producers will want a comprehensive plan, tailored for their specific facility. This necessarily involves conducting a complete risk evaluation of their dairy. The most complete description of how to implement a dairy biosecurity plan (including a pre-assessment questionnaire) is available as part of the excellent online biosecurity catalog created by the Center for Food Security & Public Health (CFSPH) at Iowa State University. For more information on CFSPH offerings see “Additional On-Line Resources” below. Other disease prevention assessment tools are available from Cornell University and Washington State University.

Dairy Expansion Programs – Because of the influx of large numbers of animals, herd expansion represents the most dangerous time for cow heath. In part because of the need to get production on-line to assist in cash flow, disease prevention is frequently overlooked. Cornell’s NYSCHAP  program has an outstanding Herd Expansion Module.  Another useful introduction to risk assessment on dairies is provided by the Bovine Alliance on Management and Nutrition (BAMN) which is a collaboration of a number of organizations including the American Association of Bovine Practitioners, the American Dairy Science Association and USDA. Other BAMN information covering a wide variety of topics are available.

Because mastitis is the most common and costly disease on most dairies, consideration of realistic milk culture programs during herd expansion is warranted.

Breeding Bull Protection – Probably no one factor has the potential to adversely affect reproduction then an infertile or diseased bull. One California survey (Champagne 2002) found that while nearly 90% of the state’s dairies employed natural service bulls, 67% of bulls had not received an evaluation of breeding soundness. A pilot survey of biosecurity practices on California dairies found that out of 38 recently purchased bulls, six (16%) had evidence of reproductive tract problems that could have impaired fertility. A comprehensive review of health care and biosecurity recommendations for natural service bulls (including prevention of venereal diseases) is available.

Fair and Show Animals – The 1996 NAHMS survey found that 26% of dairy operations over 200 cattle had animals leave and return for fairs and shows. Ultimately some producers will decide bringing show animals back from a fair is a risk they are unwilling to accept. For others however fairs and shows represent an important part of their marketing program.  While biosecurity requirements will vary from fair to fair in general the same principals as those for entry of commercial cattle apply. Vaccination and isolation of returning fair animals (see above) are particularly useful precautions. The University of Nebraska offers a fact sheet specific for biosecurity of youth events. A  webinar recording reviewing biosecurity for fairs and shows is available. For more general youth training on biosecurity, the University of California has a curriculum for 4-H participants. 

Disease Specific Programs – Producers who have experienced a problem with a particular disease (or know colleagues that have) may wish to focus on biosecurity procedures specific to that disease. There are excellent websites and “how-to guides” available addressing a number of economically important diseases:

  •  Johne’s Disease

Johne’s Information Central

Cornell University

  • Bovine Leukemia

Michigan State University

Cornell University

  • Bovine Viral Diarrhea

Cornell University

Dairy Herd Management

  • Salmonella

University of Wisconsin

Cornell University

Foreign Visitors on Your Dairy – As international trade increases so do requests for dairy tours for foreign visitors. Some visitors from countries with important endemic Foreign Animal Diseases (like Hoof and Mouth) may be have inherently more risk than visitors from other counties. The California Department of Food and Agriculture has produced a fact sheet on foreign animal disease biosecurity and a brochure specifically addressing foreign visitors. In addition the University of California – School of Veterinary Medicine’s Dr. Pam Hullinger developed this fact sheet for the California Milk Advisory Board.

Emergency Biosecurity Plans – In the event of entry of a catastrophic foreign animal disease, like Hoof and Mouth Disease or Rinderpest, enhanced emergency biosecurity measures would need to be taken to protect your dairy.  The Secure Milk Supply (SMS) allows producers and processors to work with State and Federal planners to pre-approve emergency bio-security plans, which when implemented and certified would allow continued milk shipments even within a quarantine zone. These emergency biosecurity standards (such as restricted entry and potentially vehicle washing) would be temporary, in place only while the disease was being controlled and eliminated.

Additional On-Line Resources

Center for Food Security & Public Health (CFSPH) at Iowa State University   – The most comprehensive catalog of biosecurity guidance available, this website contains white papers, slide sets (with speaker notes), posters, handouts, signage and videos related to Biological Risk Management (BRM). An entire section of the website is specific for dairy cattle.

New York State Cattle Health Assurance Program (NYSCHAP): Herd Expansion Module   – The NYSCHAP Herd Expansion module contains a information fact sheets, a risk assessment documents and slide sets. Just as useful there are

Washington State University Website: Biosecurity  – In addition to several interesting articles and links this website contains a particularly easy to read disease prevention assessment tool.

Biosecurity Articles on eXtension  – “eXtension” is the largest Cooperative Extension research-based learning network in the nation. A quick search for “biosecurity” will yield dozens of papers, links and recorded webinars that can be useful.

Secure Milk Supply (SMS) Plan  – The Secure Food Supply (SFS) is a collaborative program which is planning for business continuity (movement of product) even in the face of an outbreak of a foreign animal disease, like Hoof and Mouth Disease.  The SFS program is a USDA, University, industry and state collaboration with component programs for milk, eggs, broilers, turkeys, pork and beef. Dairy producers and processors with pre-approved biosecurity plans would be allowed to continue to ship product even within a quarantine area.

National Animal Health Monitoring System (NAHMS) Reports & Bovine Alliance on Management and Nutrition (BAMN) Fact Sheets.  – The National Animal Health Monitoring System (NAHMS) is a USDA program which conducts national studies on health and management of livestock and poultry populations. All of NAHMS dairy studies are available at this site. Also available on this page are recommendations from the Bovine Alliance on Management and Nutrition (BAMN), a collaboration of a number of organizations including the American Association of Bovine Practitioners, the American Dairy Science Association and USDA.

* Our sincere thanks to contributors & reviewers for this project:

 Dr. John Adaska, California Animal Health & Food Safety Laboratory

Dr. Pat Blanchard, California Animal Health & Food Safety Laboratory

Dr. Richard Breitmeyer, California Animal Health & Food Safety Laboratory

Dr. John Champagne, Veterinary Medicine Teaching and Research Center UCD

Dr. Pam Hullinger, Veterinary Medicine Teaching Hospital, UCD

Dr. Ann Ikelman, California Department of Food and Agriculture

Dr. Annette Jones, California Department of Food and Agriculture

Dr. Dale Moore, Washington State University

Denise Mullinax, California Dairy Quality Assurance Program