Vet Column 9-7-09
Fort Collins, Colo.
Young, weaned beef calves in many marketing channels are exposed to substantial stressors with changes in environment and nutrition, unfamiliar social interactions involved with commingling, and transport to new production facilities. Shipping fever, now better known as bovine respiratory disease (BRD), has long been a disease of concern for cattle producers. Numerous studies have shown BRD to have a negative impact on health, treatment costs, performance, and carcass quality.
BRD is the result of interaction between primary respiratory viruses (bovine herpes virus 1 (also known as IBR or infectious bovine rhinotracheitis), parainfluenza 3 virus (PI3), bovine virus diarrhea virus (BVDV), and bovine respiratory syncytial virus (BRSV), bacteria (Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni), and stress. Increasing the degree of immunity in a group of cattle prior to the anticipated exposure to respiratory tract pathogens will usually decrease the severity and number of clinically affected individuals.
With high risk feeder cattle, the challenge is to enhance the degree of immunity while minimizing stress. Veterinarians frequently recommend the use of modified live (viral vaccine that is very unlikely to cause clinical disease, but multiplies within the calf to increase immune system exposure as opposed to killed viral vaccines which only stimulate with what was injected) respiratory vaccines shortly after arrival at either backgrounding, preconditioning, or feedlot facilities with a subsequent vaccination in one to two weeks. Because stress is involved with the recent transportation, commingling, and handling, it is difficult to predict the success of the vaccine. Administering the second dose is believed to stimulate the immune system in the group of stressed individuals that failed to respond to the first does of vaccine.
Investigators from Oklahoma State University; Palo Duro Consultation, Research, and Feedlot; and Intervet, Incorporated recently published a study comparing the health, performance, and carcass merit of high risk cattle vaccinated once versus twice against the common viral respiratory tract pathogens using a modified live viral vaccine combination.
Eight truckloads totaling 612 cattle weighing 483, plus or minus 52 pounds, were purchased from different cattle auctions in Arkansas and Oklahoma during the last two weeks of January, 2006. They were delivered to the research facility in Stillwater, Okla. – 221 bulls and 391 steers were used in the study, each treatment group having the same proportion of bulls and steers. All calves were vaccinated with the modified live viral respiratory vaccine approximately 16 to 48 hours following arrival. The two dose vaccine treatment group received the second vaccination 11 days later.
The results of this study indicate that vaccinating once with a modified live respiratory virus vaccine was as effective as vaccinating twice in the prevention of bovine respiratory disease of high risk cattle. In this study, calves that received two doses of vaccine following arrival demonstrated improved feed efficiency during the finishing period.
It is important to understand that many variables may contribute to one’s definition of high risk cattle. Since bacteria also play a role in the development of BRD, accurately describing what high risk means is important in developing a receiving plan with your veterinarian. This particular study also references many other studies that indicate the superior health and performance of calves managed well and optimally vaccinated against BRD, both viral and bacterial, prior to weaning and entering commerce.
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