Can Vaccinating Beef Cows in The Fall Offer The Same Protection as Spring Vaccination?

Background

Neonatal calf diarrhea (NCD) is the most common cause of calfhood illness and a major cause of antimicrobial use on cow-calf ranches. To ensure prudent antimicrobial use, disease prevention strategies need to be encouraged. However, strong scientific evidence is needed about which practices are the most effective. Pre-calving NCD vaccination of pregnant cattle against Escherichia coli K99/F5 (E. coli), Bovine Rotavirus (BRV), and Bovine Coronavirus (BCV), as well as Clostridium perfringens is a commonly recommended strategy to mitigate this important disease.

Less than half of cow-calf producers in western Canada use NCD vaccines in their herd to improve transfer of passive immunity against these prevalent pathogens. We have previously identified using qualitative research approaches that a major barrier to the implementation of various management practices is the requirement for additional handling events. As such, we suspect that a primary reason many producers do not administer an NCD vaccine is the requirement to process heavily pregnant cows shortly before calving.

This research group has previously documented technically improper use of NCD vaccines in numerous beef herds; herds did not administer maternal NCD vaccines at appropriate times, did not administer proper booster doses, or both. Despite this, the use of an E. coli or BRV vaccine in cows at any time was associated with significantly higher serum concentrations of antibodies against these pathogens in their calves compared to calves from unvaccinated dams. Further, a higher risk of morbidity and mortality was associated with low E. coli or BRV serum antibody concentrations in calves. It was not possible to assess BCV due to reagent shortages at the time related to COVID-19; however, results would have likely been similar for that pathogen. These findings suggest that administration of an NCD vaccine outside of label recommendations may still reduce the risk of NCD in calves.

Administering an NCD vaccine at fall pregnancy diagnosis may provide adequate colostral immunity to protect calves against NCD. This practice would not align with label instructions of these products, but reducing the stress of handling pregnant cows close to calving presents an opportunity to improve both cattle and producer well-being and may increase the uptake of this advantageous practice in herds that could benefit from enhancing calfhood immunity against NCD.

Objectives

• Compare the effect of administering an NCD vaccine to pregnant dams at fall pregnancy check compared to pre-calving NCD vaccination on the transfer of maternal NCD antibodies to calves

What They Will Do

This study will explore whether blood antibody titres against E. coli, BRV, and BCV differ between newborn beef calves born to: A) 32 cows vaccinated using Scour Bos 9® at fall pregnancy check (PREG) or B) 32 cows vaccinated with Scour Bos 9® 8-10 weeks prior to the start of the calving season (PRECALV). Equal numbers of unvaccinated cows will be used as control groups. Scour Bos 9® has the longest pre-calving interval for administration and contains the greatest number of antigens amongst available NCD vaccines. Animals experiencing calving difficulty or that fail to nurse on their own soon after birth will be excluded from the study. Colostrum (immediately after birth) and calf blood (1-3d post calving) will be collected to compare IgG concentrations and specific antibodies against E. coli, BRV, and BCV between treatment groups.

The vaccine manufacturer is not involved in the study.

Implications

This study will generate preliminary evidence about whether maternal vaccines to protect calves against NCD can be effective when given at pregnancy testing