Feed Lot Magazine Online, Studies Reveal Early Immunity in Cattle From Combined-Antigen Vaccines

Using a combination of modified live and killed virus antigens when vaccinating cattle for infectious bovine rhinotracheitis (IBR) results in rapid disease immunity, according to Professor James A. Roth, D.V.M., Ph.D., of the Iowa State University (ISU) College of Veterinary Medicine. Roth reported on key findings of comparative research at a recent Merial Cow/Calf Practitioner Symposium. Dee Griffin, D.V.M, M.S., of the University of Nebraska's Great Plains Educational Center, Clay Center, Neb., presented information on the effect of passively transferred immunity (from a mother cow to calf) on disease prevention.

Roth reported that Iowa State researchers compared a control group with four groups of calves that received well-known brands of cattle respiratory vaccines. The study demonstrated that the group of calves vaccinated with the single product containing both modified live and killed forms of IBR antigens had significantly fewer clinical signs of disease than the group vaccinated simultaneously with the intramuscular killed and intranasal live vaccines, and the intranasal, modified live vaccine alone.

" Cattle challenged five days post vaccination with the product containing both modified live and killed IBR antigens developed significantly better immunity than those who received the intranasal vaccine, or a combination of that vaccine and a conventional, killed vaccine," Roth said. "This is a real advantage for producers who purchase cattle that are not preconditioned. Those cattle can be vaccinated as soon as they reach their destination, and be quickly protected from shipping fever caused by IBR."

New Technique Aids Immunology Research

In another report at the symposium, Roth described the development of a technique that uses flow cytometry to measure T-cell subset activation. Once this technology is available, it will enable more thorough testing of vaccine effectiveness, and help measure vaccine performance in the future.

" We know that antibodies and cell-mediated immunity work together to provide immunity against diseases. T-cell subset activation allows us to understand and evaluate the full immune response to vaccines."

One use of this new technology was a USDA National Animal Disease Center study of young calves' development of immunity to bovine viral diarrhea (BVD). Due to the antibodies in colostrum, nursing calves do not develop their own antibodies, even with a modified live BVD vaccine, Roth said. However, the research did show that early exposure to BVD stimulates cell-mediated immunity as a memory system, without stimulating antibody production.

Roth said the next step will be further testing to determine which vaccines, when administered to preweaned calves, will induce cell-mediated immunity and thus protect against future challenge by a virus.

Antibodies from Colostrum Prevent Diseases Throughout a Calf's Life

Related research at the University of Nebraska showed that immunity passed from the mother cow to the calf, or passive immunization, is also an important factor for disease prevention, according to Griffin, who is professor of beef production medicine and management at the university.

Failure of passive transfer (FPT) occurs when immunity is not passed on to the calf through colostrum during the first 24 hours of life. To determine the effect of FPT, researchers measured the antibody levels in two groups of calves. The first group showed an overall FPT rate of 21 percent. Fifty percent of the FPT calves became sick prior to weaning, compared with only 10 percent of calves with passive immunity.

The second group consisted of 263 calves, whose health and growth were monitored from birth to slaughter. In this group, FPT occurred in 23 percent of the calves. In the neonatal stage (birth to 28 days), 25 percent of the FPT calves became sick; preweaning death rate was eight percent; preweaning sickness rate 33 percent; and feedlot respiratory sickness rate was 55 percent.

" The second group demonstrated that the effects of sickness on calf growth are considerable," Griffin said. "Weaning weights for the calves that were sick during the neonatal stage were 35 pounds lower, and average daily gain in the feedlot was 0.09 pounds lower in the calves that experienced respiratory sickness while at the feedlot."

Effective Disease Prevention with Vaccines

" Because of the losses associated with calf sickness," Griffin said, "vaccination is extremely important, especially when calves do not have passive immunity. Immunization, however, requires an effective vaccine and a responsive calf. A calf's ability to develop resistance to a disease requires time, because the calf's immune system must develop antibodies and cell-mediated immunity to mount an effective immune response."

Griffin said in order to optimize the vaccination, vaccinate the entire herd and for all contagious diseases. Be sure to handle vaccines properly and deliver the vaccine subcutaneously, if possible, or intramuscularly in the neck region.

" In addition, calves should be at optimal health when they are vaccinated," he said. "Poor nutrition and parasite infection can suppress the immune response, thus making the vaccine less effective."

" The research at Iowa State and the University of Nebraska is important to the beef industry," said Dr. Frank Hurtig, D.V.M., manager, veterinary professional services of Merial, "because it demonstrates the value of vaccination and sets the stage for even better vaccines in the future."