Vaccinating high risk stocker calves on arrival might make the most intuitive and logistical sense, but it also might do more harm than good in some sets of cattle.

Consider recent research directed by Mississippi State University (MSU—Griffin, Scott, Karisch, Woolums, et. al), comparing the effect of vaccinating high-risk stocker calves on arrival, versus 56 days later.

“In this study, vaccinating calves at arrival was associated with increased bovine respiratory disease (BRD) morbidity, mortality, and lower final weights,” according to the study.

Specifically, calves vaccinated with a modified-live respiratory virus vaccine (MLV) and a clostridial bacterin-toxoid the first day of the trial were 3.2 times more likely to be treated for BRD and were at 8.3 times greater odds of death during the 85-day trial.

For perspective, 46.25% of all calves in the study were diagnosed with BRD at some point. Mortality across the entire population of calves was 16%, all due to BRD. Again, all calves, regardless of treatment group, were vaccinated on day 56 of the trial (see more specifics in the study here).

Calves vaccinated on arrival gained 10.3 pounds less than non-vaccinated calves on arrival, on average.

The MSU study also included researchers from North Carolina State University and the University of Georgia.

“These findings support the concept that vaccination of calves that may have been recently exposed to various stressors and are potentially incubating BRD, can increase their risk for illness,” according to the MSU researchers. “This relationship may be due in part to vaccine-induced inflammation. Vaccinating high-risk calves at arrival is a common practice, but there is limited research supporting its efficacy.”

Results build on previous research with similar conclusions.

For instance, a University of Arkansas (UA) study compared the effects of vaccinating calves with an MLV on arrival (AMLV) versus vaccinating 14 days after arrival (DMLV), during a 42-day period. It included 528 crossbred steer and bull calves.

Average daily gain (ADG) was greater for DMLV calves from day 0 to 14 (2.56 pounds) and from day 0 to 42 (1.65 pounds), compared to AMLV calves that gained 1.94 pounds and 1.43 pounds, respectively.

BRD morbidity rates were high for both AMLV (71.5%) and DMLV (63.5%) and the difference was not statistically significant. Days to first treatment, total treatment cost, percentage death loss and pasture ADG after the 42-day period did not differ.

Brian Vander Ley, DVM, a veterinary epidemiologist at Great Plains Veterinary Educational Center in Clay Center, Neb., notes, “An interesting observation about this data is that essentially all of this morbidity occurred before the delayed group received their vaccine with no apparent deleterious impact on the delayed calves.”

During a University of Nebraska Beef Webinar, Vander Ley pointed to a study conducted at Oklahoma State University (OSU). Briefly, it evaluated the health and performance of calves sent to the same Oklahoma backgrounding facility.

One group was commingled from sale barns in Mississippi. Three other groups came from the same ranch: one was weaned and shipped the same day, another weaned 45 days at the ranch before shipping and the other weaned 45 days and vaccinated at the ranch.

Morbidity was statistically similar between the commingled sale barn calves (41.9%) and those weaned and shipped the same day (35.1%). It was 5.9% for the calves weaned 45 days and 9.5% for those weaned 45 days and vaccinated.

“From this data, you can see that stress plays a huge role. Putting stressed cattle on a truck and sending them to a feedyard, even though they weren’t commingled, resulted in almost as much respiratory disease as buying calves at the sale barn with an unknown history,” Vander Ley says.

“We know there is stress associated with transport and weaning. We have commingling, which introduces both social stress and exposure to new pathogens. We have transport that introduces physiologic stress.”

John Richeson, PhD, conducted the aforementioned UA study. He is now a professor of animal science at West Texas A & M University and supervises the school’s research feedlot.

“Although the current recommendation of feedlot consulting veterinarians is nearly unanimous in favor of vaccination against respiratory viruses during initial processing of high-risk cattle, there is little research to support this recommendation,” Richeson explained during a presentation at the University of Florida Beef Short Course in 2018.

“Vaccine efficacy hinges upon a robust immune response to the antigens contained in the vaccine, and the immune system requires several days to weeks to respond adequately. Furthermore, stress may alter the immune system’s ability to respond to a vaccine, and stress is reduced when vaccination is implemented at the ranch origin versus feedlot arrival.”

Richeson also pointed out a negative control is rarely used in studies evaluating the timing of vaccination, effects of revaccination, or comparing different vaccine products.

“The data supporting vaccination at arrival in North American feedlots are equivocal at best, and some studies of arrival vaccination suggest it does not benefit or may even decrease health performance,” say MSU researchers.