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Biosecurity for Beef Cow-Calf Operations: Managing the Entry of New Animals

Updated February 22, 2021
Professional headshot of Russ Daly

Russ Daly

Professor, SDSU Extension Veterinarian, State Public Health Veterinarian

Two producers moving cattle out of a shelter.
Courtesy: Preston Keres, USDA/FPAC

Infectious disease can impact cow-calf operations in dramatic (death losses and illnesses) and not-so-dramatic (drains on weight gain and reproductive performance) ways. Some of these disease issues are caused by endemic germs (those found normally in a herd’s animals), while other problems arise after a novel germ has found its way onto an operation. These novel disease issues tend to be more noticeable and impactful, as herd animals generally have no immunity to these new pathogens. Keeping novel germs out of a herd is therefore of great importance to cow-calf producers.

Interventions that prevent the introduction of novel infectious disease agents into a population are termed “biosecurity.” Disease agents can enter a cow-calf operation in various ways, including through fenceline contact with other herds, people or vehicle movement onto a farm, wildlife and rodents, contaminated equipment, or contaminated feed.

As biosecurity threats, new animals entering the herd are more important than those other routes of entry. Animals carrying disease agents have more extensive contact with animals compared to other carriers and can transmit germs to other animals in ways not possible with other routes of entry. Disease agents multiply in infected animals but do not do so on inanimate objects, making animals a more effective source of infection. A pertinent example is that of calves purchased to foster onto cows who have lost their calves. The new arrivals represent a high risk for bringing new scours agents into a herd.

While not technically new to a herd, show animals that have had contact with other cattle and cattle environments should be considered newly exposed and potentially infected. They should be managed in the same manner as a new purchase. Animals traveling to and returning from several shows in a season may need to be isolated for extended periods of time.

Isolating and testing animals coming into the cow-calf operation are the main tools employed in maintaining animal-related biosecurity. The advice of the herd’s veterinarian will be invaluable in implementing these procedures – and should be sought well in advance of the arrival of new animals.


The cornerstone of any biosecurity program is isolation and observation of new animal additions upon arrival. Effective isolation includes time and separation considerations. The isolation period should be at least 30 and preferably 60 days. This period is sufficient to allow any acute disease to develop if infection was acquired shortly before movement and will allow time for the animal to stop shedding other potentially harmful germs.

During the isolation period, new arrivals should have no contact with the home herd. This includes direct nose-to-nose contact and contact with manure and contaminated water and feed. Equipment, vehicle, and people movement between the isolated group and the home herd should be managed to limit disease agent transmission through these routes.

Diagnostic Testing

Certain important cattle diseases lend themselves well to diagnostic testing strategies while new animals are in isolation. Some diseases present themselves in persistent forms, such that no isolation period is long enough for the animal to stop shedding the germ – e.g., trichomoniasis in bulls and persistent infections with Bovine Viral Diarrhea Virus.

For other important diseases, such as Johne’s Disease, diagnostic testing is of little use as current tests do not identify animals in early stages of infection. Regardless of the tests chosen, producers should have a clear plan for managing any animals found to be infected.

Minimum Biosecurity Considerations

These steps should be considered minimum standards for introducing new animals into cow-calf operations. The herd’s veterinarian can provide recommendations specific to the farm and geography. In many cases, the veterinarian can contact the veterinarian of the purchased animals, allowing for a more specialized transfer of information that can help inform biosecurity-related decisions.

Open Replacement Heifers

  • Isolate for 30-60 days.
  • Ear notch test for BVDV persistent infection while in isolation.
  • Vaccinate to coordinate with the existing herd’s vaccination status.

Bred Cows and Replacement Heifers

  • Isolate and keep separate until calves are born and BVDV tested (minimum of 30 days).
  • Ear notch test calves for BVDV persistent infection.
    • If positive, ear notch test the dam for BVDV.
  • Vaccinate to coordinate with the existing herd’s vaccination status.


  • Isolate for 30-60 days.
  • Ear notch test for BVDV persistent infection while in isolation.
  • (Non-virgin bulls) Confirm results of trichomoniasis testing performed prior to sale (requirement prior to change of ownership in South Dakota).
  • Vaccinate to coordinate with the existing herd’s vaccination status.

Foster Calves

  • Isolate (with dam) for 30-60 days.
  • Ear notch test for BVDV persistent infection while in isolation.
  • Vaccinate to coordinate with the existing herd’s vaccination status.