Brucellosis Laws in Colorado: What Cattle and Bison Owners Need to Know

If you raise cattle or bison in Colorado, brucellosis regulations directly affect how you move, test, vaccinate, and manage your herd. Violating these rules — even unintentionally — can trigger quarantines, forced depopulation, and significant financial penalties.

Colorado has worked hard to earn and keep its Certified Brucellosis Free designation, and the state’s rules are designed to protect that status. Whether you are importing animals from another state, managing a certified free herd, or simply trying to understand your reporting obligations, this guide walks you through every layer of Colorado’s brucellosis framework.

What Is Brucellosis and Why It Is Regulated in Colorado

Brucellosis is a contagious bacterial disease that poses serious risks to both livestock operations and public health. It is a contagious, infectious, and communicable disease primarily affecting cattle, bison, and swine, caused by bacteria of the genus Brucella. Brucella abortus primarily affects bovine species, though goats, sheep, and horses are also susceptible.

In its principal animal hosts, brucellosis causes loss of young through spontaneous abortion or birth of weak offspring, reduced milk production, and infertility. It can affect both animals and humans. For livestock producers, a single infected herd can result in devastating economic losses and trigger mandatory depopulation.

It is important to note that brucellosis is present in free-ranging bison and elk in Yellowstone National Park, Grand Teton National Park, and the area around those parks. Although Colorado is not in the immediate Greater Yellowstone Area, the disease’s persistence in wildlife across the broader region is precisely why Colorado maintains active surveillance and strict import controls.

Brucellosis is transmitted from animals by direct contact with infected blood, placentas, fetuses, or uterine secretions, or through the consumption of infected material. The regulations of the APHIS Brucellosis Eradication Program vary based on the brucellosis status of each state. Colorado’s rules reflect its high-status standing and its commitment to keeping the disease out of the state’s cattle and bison herds. You can find similar regulatory frameworks in neighboring states — for example, see how brucellosis laws in Nebraska compare to Colorado’s approach.

Colorado’s Brucellosis Classification Status

Colorado holds the highest possible brucellosis classification under the federal system. It is the purpose of the State Veterinarian’s Office to maintain Colorado’s Certified Brucellosis Free Status and further reduce the possibility of infection to the cattle and bison within Colorado.

States are designated brucellosis-free when they have no infected cattle or bison for 12 consecutive months under an active surveillance program, or when additional surveillance measures are in place around areas that have brucellosis-infected wildlife to ensure early detection of any disease spillover.

All 50 states, Puerto Rico, and the U.S. Virgin Islands are brucellosis-free, except for the occasional spillover of cases occurring in livestock near the Greater Yellowstone Area due to bison and elk having the disease. Colorado is listed among the validated brucellosis-free states under 9 CFR Part 78, which governs the federal brucellosis classification system.

The classifications under federal regulations are Class Free, Class A, Class B, and Class C. States or areas that do not meet the minimum standards for Class C status are required to be placed under federal quarantine. Restrictions on moving cattle and bison interstate become less stringent as a state or area approaches or achieves Class Free status.

Methods for maintaining free status include continuation of slaughter and sale surveillance programs, control of import animals appropriately by origin and use, and vaccination as long as it is an effective tool. The preferred method of management of any infected Colorado herd is indemnified depopulation pending available federal or state funds.

Vaccination Requirements in Colorado

Colorado takes a voluntary but tightly regulated approach to brucellosis vaccination. Understanding the rules around who can vaccinate, which vaccine is approved, and how vaccinated animals must be identified is essential for any producer who chooses to vaccinate their herd.

Voluntary Status and Approved Vaccine

Vaccination for brucellosis is voluntary in the state of Colorado. However, if you choose to vaccinate, you must follow strict protocols. Vaccination for brucellosis may only be administered by an accredited veterinarian.

Any brucellosis vaccination of beef, dairy, and bison heifer calves must be with strain RB-51 and may only be administered between 4 and 12 months of age. Licensed for use in nonpregnant female cattle 4 to 12 months of age, the RB51 vaccine provides a significant level of protection — about 70 to 80 percent effective.

Identification and Reporting Requirements

Once a heifer is vaccinated, specific identification and documentation steps are mandatory. Vaccinated heifers shall have legible brucellosis vaccination tattoos and official ear tags. Any vaccination performed shall be reported by the accredited veterinarian on an official vaccination certificate (VS Form 4-24) to the USDA within 30 days of vaccination.

The tattoo applied to the right ear follows a standardized format. For B. abortus Strain RB51 vaccinates, the tattoo will include the letter “R” for RB51, the U.S. Registered shield and “V,” and the last digit of the year in which the vaccination was conducted.

Why Vaccination Still Matters

All cattle or domestic bison owners, regardless of location, should discuss the advantages and disadvantages of vaccination with their veterinarian. Some states don’t allow cattle or domestic bison to be moved interstate for breeding without a record of brucellosis vaccination. If you plan to sell or move animals out of state, confirming the destination state’s OCV requirements before transport can save you significant delays and costs. You can review how vaccination rules compare in states like Minnesota and Missouri to understand what your buyers may require.

Testing Requirements for Cattle and Bison in Colorado

Colorado’s testing requirements vary significantly depending on whether the movement is within the state or crosses state lines, and on the brucellosis status of the origin state.

Intrastate Testing

In the absence of evidence of exposure to test suspect or positive cattle or bison, there is no testing requirement for change of ownership or movement within Colorado. This reflects Colorado’s Class Free status — internal movement is generally unrestricted unless a known exposure risk exists.

Interstate Import Testing

The rules tighten considerably when animals enter Colorado from other states. Official Calfhood Vaccinate (OCV) cattle over 12 months of age and bison over 6 months of age may enter Colorado without a test and shall be individually identified with an OCV ear tag with the ear tag number recorded on a certificate of veterinary inspection.

All non-OCV beef cattle over 12 months of age and bison over 6 months of age entering Colorado must test negative for brucellosis with an approved test within 30 days prior to entry. All such animals must be individually identified with an RFID electronic ear tag with the RFID number recorded on the certificate of veterinary inspection.

Animals from certified free herds receive a simplified pathway. Cattle from Certified Free Herds may be imported into Colorado without a test for brucellosis. The certified free herd number, issued by the state animal health officials in the state of origin, must be listed on the certificate of veterinary inspection.

Certified Free Herd Qualification

If you want your herd to qualify for Certified Brucellosis-Free status, the bar is high. At least two consecutive negative approved blood tests of all test eligible cattle or bison not less than 10 months, nor more than 14 months apart, are required for initial certification.

Maintaining certification requires ongoing testing. A negative herd test of all test eligible animals conducted within 60 days of each anniversary date is required for continuous certification. If a herd test for recertification is not conducted within 60 days following the anniversary date, then certification requirements are the same as for initial certification.

Test Documentation and Lab Requirements

All brucellosis tests needed for movement or change of ownership shall be forwarded to the CDA Animal Health Laboratory (AHL) on a VS Form 4-33 whenever any livestock are tested. Any tested livestock shall be officially identified.

The Colorado Department of Agriculture Animal Health Lab (CDAAHL) is the only lab in the state to offer official brucellosis testing for B. abortus, B. melitensis, and B. suis. This testing covers any movement, including shows and change of ownership.

Interstate and Intrastate Movement Rules in Colorado

Colorado’s movement rules are among the most structured aspects of its brucellosis regulatory framework. The rules differ based on the origin state’s classification, the type of animal, and the purpose of the move.

Movement Within Colorado

As noted above, intrastate movement carries no brucellosis testing requirement in the absence of known exposure. However, all animals must be officially identified, and a Certificate of Veterinary Inspection (CVI) is required for most commercial transactions. A CVI shall be void thirty days after the date of its issuance. Plan your transport timing accordingly.

Importing from Class Free States

When you bring animals in from other Class Free states, the requirements hinge on OCV status. OCV animals over the applicable age thresholds may enter without a brucellosis test, while non-OCV animals require a negative test within 30 days of entry. Additions to a certified free herd from non-free states must test negative to an approved brucellosis test within 30 days prior to shipment and be isolated on the certified free herd premises and retested within 45 to 120 days after arrival.

Importing from Class B or C States

Colorado applies a strict prohibition when it comes to animals from lower-classification states. No bovine or bison originating from Class B or C states may enter Colorado. This absolute restriction protects Colorado’s Class Free standing and is non-negotiable regardless of individual animal test results.

Similarly, no female cattle, regardless of age or vaccination status, from a herd under quarantine for brucellosis may enter Colorado unless shipped directly to a federally inspected slaughtering establishment, to a quarantined feedlot, or to an approved market for sale to slaughter.

Commuter Herd Agreements

Colorado offers a practical option for ranchers who regularly move livestock across state lines. A commuter agreement may be obtained by herd owners for the purposes of moving livestock into Colorado from contiguous border states and returning to the state of origin, or for moving livestock from Colorado to border states and then returning to Colorado. This arrangement eliminates the need for repeated brucellosis testing on routine cross-border grazing movements, provided a formal agreement is in place with both states’ veterinarians.

Exhibition and Show Animals

All cattle, regardless of age or sex, for exhibition, show, rodeo, or recreational events need to be individually identified with official ID ear tags, and the official ear tag number needs to be listed on the certificate of veterinary inspection (CVI). Out-of-state exhibition animals must also meet brucellosis testing or OCV documentation requirements before entry.

For a broader look at how Colorado handles animal import regulations across species, the state’s pet import laws offer useful context on the state’s general approach to animal movement controls.

Reporting and Quarantine Requirements in Colorado

When brucellosis is detected or suspected in a Colorado herd, the regulatory response is immediate and comprehensive. Understanding your reporting obligations and what to expect during a quarantine is critical for any livestock producer.

Reporting Obligations

Animal health professionals — including veterinarians, diagnostic laboratories, public health personnel, zoo personnel, wildlife personnel, and others — report diagnosed or suspected cases of nationally listed reportable animal diseases to APHIS Area Veterinarians in Charge and to the state animal health official as applicable under state reporting regulations. In Colorado, brucellosis is a reportable disease, and any confirmed or suspected reactor must be reported promptly to the Colorado Department of Agriculture.

If infection is suspected or confirmed, regulatory officials will contact you, the owner, or both, to develop a herd plan. Cooperation with state and federal officials during this process is not optional — it is a legal requirement under Colorado’s livestock disease control statutes.

Quarantine Procedures

Once a reactor is identified, quarantine is automatic and comprehensive. In herds where a reactor animal is disclosed, all cattle or bison in the herd shall be quarantined on the premises.

A quarantine is a written notice or order issued by an authorized agent of the Colorado Department of Agriculture showing the boundaries of the area or premises affected, the animals restricted, and the conditions, if any. No livestock held under quarantine may be moved or released until a VS-127 permit or quarantine release signed by an authorized agent has been issued.

Movement of Quarantined Animals

Even under quarantine, limited movement is permitted under specific conditions. The herd owner may ship suspect or reactor cattle or bison, or other animals within the quarantined herd, directly to slaughter under a VS Form 1-27 permit.

Affected herds shall remain under quarantine until such time that they are depopulated or all reactor or suspect cattle or bison have been removed from the herd and the remaining cattle or bison test and retest negative in accordance with the terms of the quarantine. This can be a lengthy and costly process, underscoring the importance of prevention.

Depopulation as the Preferred Outcome

Colorado’s regulations make clear that depopulation is the preferred resolution for infected herds. The preferred method of management of any infected Colorado herd will be indemnified depopulation pending available federal or state funds. Indemnity payments may be available through cooperative federal-state programs, but they are not guaranteed and depend on funding availability at the time of the event.

Colorado’s approach to quarantine and disease control shares structural similarities with other states. You can review how Michigan’s brucellosis laws and Nevada’s brucellosis laws handle quarantine and depopulation for a broader comparison.

Penalties for Brucellosis Violations in Colorado

Colorado enforces its brucellosis regulations under the broader authority of its livestock disease control statutes, primarily codified in Title 35, Article 50 of the Colorado Revised Statutes (C.R.S.). Violations can carry serious administrative, civil, and financial consequences.

Administrative Penalties and Regulatory Enforcement

The Colorado Department of Agriculture has broad authority to enforce brucellosis regulations. Violations can include moving quarantined animals without a permit, failing to report a reactor, importing animals from prohibited states or herds, and failing to comply with testing or identification requirements.

Under Colorado’s livestock disease control framework, the CDA may issue stop-movement orders, hold orders, and quarantine notices. A “hold order” is a written notice or order issued pursuant to Section 35-50-103(5) C.R.S. when the results of tests are pending. Violating a hold order or quarantine notice is a separate and additional offense under state law.

Civil and Criminal Liability

Colorado law provides for civil penalties against any person who knowingly violates livestock disease control regulations. Intentional movement of brucellosis-infected or exposed animals without a permit, or falsification of veterinary inspection certificates, can expose you to criminal charges under Colorado’s agricultural fraud statutes. Penalties may include fines, loss of livestock operation licenses, and in serious cases, criminal prosecution.

Beyond direct regulatory penalties, you may also face civil liability from neighboring producers if your animals spread disease to their herds. Colorado’s livestock disease laws do not shield negligent producers from civil suits brought by affected parties.

Indemnity Forfeiture

One of the most significant financial penalties for non-compliance is the forfeiture of indemnity payments. If you move, conceal, or otherwise interfere with the regulatory management of a brucellosis-affected herd, you may forfeit your eligibility for state or federal indemnity payments that would otherwise compensate you for depopulated animals. This can represent tens of thousands of dollars in lost compensation.

Staying Compliant

The best way to avoid penalties is to stay ahead of your obligations. Keep all vaccination certificates, test records, and CVIs organized and accessible. Work with an accredited veterinarian for all testing and vaccination activities. Submit VS Form 4-33 test records to the CDA Animal Health Laboratory promptly, and never move animals under a hold order or quarantine without written authorization from the Colorado Department of Agriculture.

Colorado’s animal regulations extend well beyond brucellosis. If you manage livestock or other animals in the state, you may also want to familiarize yourself with Colorado’s animal cruelty laws and wildlife removal laws, both of which can intersect with livestock management practices. For producers managing multiple species, Colorado’s backyard chicken laws and rooster laws are also worth reviewing.

Understanding and following Colorado’s brucellosis laws is not just a legal obligation — it is an investment in the long-term health and value of your herd. Colorado’s Class Free status benefits every producer in the state through reduced testing burdens, fewer interstate movement restrictions, and stronger market access. Protecting that status starts with every individual operation doing its part.