Livestock vet prepares to give cow an oral vaccine in barn.

Livestock Disease Protection Starts Before Birth

Livestock | October 2025

Written by:

Jennifer Ryan has been writing about veterinary topics for nearly 20 years. She has a master’s degree in journalism, a bachelor’s degree in agricultural communications and decades of experience caring for both livestock and pets.

Vaccines providing fetal protection can help prevent disease in calves even before they hit the ground.

With record low cattle inventories, producers can expect calves will continue to be valuable for years to come. The best action to take with high-ticket items is to protect them as early as possible, and that can start even before conception.

“Why do we vaccinate female adult cattle? It’s for the calf while it’s in utero,” explained Dan Tracy, DVM, MS, Beef Technical Service veterinarian at Zoetis. “With today’s value in calves, every head increase in our calf crop equals a lot of dollars back to the producer.”

Assessing disease threats

Tracy recommends producers work with their veterinarian to evaluate the risks to their herds. This can include biosecurity risks from purchased replacements, past reproduction issues on the operation or fence-line risks from neighboring herds.

The most common disease threats from breeding through birth include:

  • Vibriosis (Campylobacteriosis), a bacterial infection caused by Campylobacter fetus, which can cause infertility and abortions
  • Leptospirosis caused by the serovar Leptospira hardjo, which can cause abortions or weak/stillborn calves
  • Infectious Bovine Rhinotracheitis (IBR), which can affect the cow’s respiratory and reproductive systems
  • Bovine Respiratory Syncytial Virus (BRSV) and Parainfluenza Type 3 Virus (PI3) that may cause respiratory signs and allow for secondary bacterial pneumonia
  • Bovine Viral Diarrhea (BVD), which can cause abortions, stillbirths and/or birth defects

Cows not properly vaccinated for fetal protection and exposed to BVD between 40 to 125 days of pregnancy may deliver a persistently infected (PI) carrier calf. For the rest of its life, this PI calf will shed BVD virus that can then infect other animals.

“BVD is the gift that keeps on giving, and it’s not a good gift,” Tracy said. “It’s the Typhoid Mary of the calf crop, spreading disease and death. BVD infection can go undetected in the herd. Then, when we start turning the bulls in, those calves are still cow-side, and it becomes a multiplier event.”

 

Very healthy dairy cow in field

 

Selecting protection

After assessing the operation’s risks, the next step is selecting a vaccination program that will help protect against the major disease threats while working into the herd’s established protocols.

“On the market today, we have modified live vaccines (MLV), killed vaccines and vaccines that straddle the line,” Tracy said. “Sometimes we get one chance to work that herd and want a product with a long duration of immunity. To get fetal protection, it’s important that we choose vaccines that have demonstrated fetal protection as part of the approval process, have specific indications for fetal protection and are going to last through the gestation period.”

Tracy cautions that young heifers or cows that are not on an MLV program must receive two rounds of vaccines prior to breeding. Then, producers can routinely vaccinate with MLVs during gestation with confidence.

“Vaccinating replacements is a good place to start,” he said. “When you pull young females off the cow, start modified live vaccines with fetal protection during that time to help build immunity prior to breeding.”

Colostrum bridges the immunity gap

After birth, colostrum is the final key to ensuring calves have the healthiest start, and it’s especially important during unpredictable weather.

“Calving in spring is wet and cold; that means calves are subject to viruses and bacteria that can cause scours,” Tracy explained. “Colostrum comes from the immunocompetence of the dam.”

Immunocompetence can be boosted by additional vaccinations during gestation for scours and respiratory disease. Some scour vaccines may be given to cows before calving and help provide early protection against rotavirus, E. coli and Clostridium perfringens. An adequate uptake of colostrum can help pass valuable antibodies built through a well-managed vaccination program to the calves. Yet, calves are still susceptible to common respiratory disease challenges once on the ground.

Producers can consider an intranasal vaccine before parturition to help boost antibodies for common pathogens like BRSV and IBR.

“It’s important to meet with your veterinarian to see when these vaccines can be put into place,” Tracy confirmed. “Producers who have invested in AI and bought into some really good genetics already have a fair amount of commitment per cow to get an offspring on the ground. If we’re going to do that, invest in vaccines.”

 

Veterinarian giving a dairy cow an oral vaccine.

 

Be aware of biosecurity

The high value of calves in the current market demands attention to the entire herd’s disease prevention program. Producers may be tempted to bring in replacements with an unknown vaccination status to grow herd numbers.

A solid vaccination program is the back-up plan for biosecurity failures that simply happen in the everyday management of a cattle operation.

“Now that we’re rebuilding the cow herd, replacements are bringing a premium, but what is the status of the calf they are carrying? Anytime you have new introductions, you have to test,” Tracy recommended. “Producers are building a quality calf, and it’s a valuable product.”

Key points

  • The fetus does not develop a protective immune response until the third trimester.
  • Vaccination programs can help improve colostrum quality to help calves fight off early infection.

 

Photo credits:

  • istockphoto.com/mladenbalinovac
  • istockphoto.com/Natallia Saksonova
  • istockphoto.com/jenoche
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