Higher feed costs have resulted in backgrounded cattle staying on grass longer to reach heavier weights before entering the feedyard. By the time these calves get to the feedyard at 9 to 12 months of age, they are primed for revaccination against major respiratory diseases.

A recent study published in Bovine Practitioner provides guidance on selecting the most effective vaccine type for these calves, based on their prior vaccination history. Specifically, if calves were vaccinated with a modified-live vaccine (MLV) at weaning, the study found that using an inactivated vaccine at feedlot arrival provides better disease protection than an MLV.

“This study is significant because it provides scientific confirmation of what we’ve seen in the field for years,” said Dr. Dennis Hermesch, professional services veterinarian with Novartis Animal Health. “And that is cattle receiving a priming dose of modified-live vaccine and a booster dose of inactivated vaccine are less likely to get sick than cattle receiving only modified-lives.”

The study monitored a group of 45 calves that had received an MLV vaccine at one to two months of age. The calves were revaccinated with the same MLV vaccine at weaning. Approximately five months later, the calves were divided into groups. One group received the same MLV they had received as calves. Another group received Vira Shield®, an oil-adjuvanted, inactivated vaccine.

Following the final vaccination, calves in the group that had been revaccinated with Vira Shield had significantly higher titer response for IBR, BRSV and BVDV Types 1 and 2. A higher titer response for these diseases on feedlot arrival has been associated with a reduced risk of BRD and increased weight gain.

In reviewing previous published studies, the report in Bovine Practitioner also indicates that vaccinating nursing calves with a combination of MLV and inactivated vaccines may induce a better immune response than using either vaccine type alone. An inactivated vaccine may be more effective to booster an MLV because it can provide a more consistent humoral immune response, resulting in higher antibody levels than produced by an MLV vaccine alone.

Conclusions of the study published in Bovine Practitioner indicate that vaccinating backgrounded cattle with an inactivated vaccine may reduce morbidity associated with bovine respiratory disease (BRD) at the feedyard.

Dr. Hermesch added that this study has implications for replacement heifers as well. “Many replacement females are vaccinated two times around weaning and then boostered again prior to first breeding,” he said. “Although the study was conducted with backgrounded cattle, I think the same lesson applies for replacement females. Using an inactivated vaccine on heifers that received a modified-live at weaning may well result in better, longer-lasting response to reproductive pathogens such as BVD and IBR.”

1. Royan G. Comparison of the BVDV, BHV-1 and BRSV Anamnestic Response to Modified-live or Inactivated Vaccines in Calves Previously Vaccinated with a Modified-live Virus Vaccine, The Bovine Practitioner, Spring 2009.

Source: Novartis Animal Health