Authored by:  Paola P. Boscollo, PhD, & João H.J. Bittar, DVM, MSc., PhD, UF/IFAS Beef Cattle Veterinarian

Vaccinating pregnant cows and heifers in the last trimester of gestation is the most effective strategy to improve colostrum quality (milk secreted for a few days after birth characterized by high protein and antibody content), which is determined by antibody concentrations. Colostrum quality is directly related to the protection of newborn calves from disease during the first months of life. This protection relies primarily on passive transfer of maternal antibodies through colostrum; therefore, the calf must ingest high-quality colostrum as soon as possible after birth to receive this important immunity.

Among the most important pathogens causative of neonatal calf scours in beef herds are Bovine Rotavirus (BRV) and Bovine Coronavirus (BCV). BRV most commonly affects calves between 5 and 14 days of age by infecting the small intestine. In contrast, BCV is more frequently observed during the first month of life, infecting both the small and large intestines and even causing respiratory disease. These infections can lead to higher calf morbidity (sickness) and mortality (death) in calves under 60 days of age, reduced weight gain, higher treatment costs, and extra labor for producers. Some of these challenges are even greater in our subtropical conditions, where heat stress is a constant issue year-round.

However, prepartum (last trimester) vaccination is not widely adopted by beef cattle operations. Common reasons include, but are not limited to, extra cattle handling, lack of knowledge about the vaccines, extended or uncontrolled breeding seasons that make gestation time unclear, a preference for vaccinating newborn calves instead of the mother, and the belief that vaccine costs outweigh disease risks.

In our recent study, funded by the Florida Cattle Enhancement Board, entitled “Optimal timing for vaccinating pregnant beef heifers: impact on colostrum quality and calf health”, preliminary findings showed a numerical difference in colostrum antibody quality (measured as antibody titers in colostrum) depending on when the dam was vaccinated (gestation stage). Specifically, vaccinating pregnant females 77 days before calving (on average) resulted in higher colostrum antibody titers than vaccinating at 97 days before calving. We also found that vaccinating the pregnant females closer to calving improved calf blood protection levels (measured as serum neutralizing antibody titers) during the first month of life for both BRV and BCV. Furthermore, our findings confirmed that first-calf heifers (primiparous) produced colostrum with lower antibody titers than mature cows (multiparous) following prepartum vaccination (Figure 1).

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Ultimately, prepartum vaccination is not just an extra chore; it is an investment in the health your herd. Protecting your calf crop starts well before calving, and timing is everything. Because every operation has unique breeding seasons, handling constraints, and environmental challenges, there is no single rule for every ranch. This is why building a strong Veterinary-Client-Patient Relationship (VCPR) is essential to ensure that you work with your herd veterinarian to build practical prepartum vaccination protocols tailored to your herd. Doing so ensures your calves get the best start possible, safeguards your calf crop, and prevents costly losses from calf scours.

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