Proceedings, Applied Reproductive Strategies in Beef Cattle

Introduction Bovine Viral Diarrhea (BVD) virus and Infectious Bovine Rhinotracheitis (IBR) virus are two of the major viral pathogens responsible for respiratory disease in cattle. These viral agents can be associated with pathology in the respiratory, immunologic, neurologic, hematologic, lymphatic, and reproductive organ systems (Grooms et al., 1998). Infections of cattle with BVD virus and/or IBR virus are associated with reduced conception rates, early embryonic mortality, and reduced pregnancy rates. Proper vaccination protocols are a key part of the prevention and control of losses due to these agents. Current recommendation for vaccination of cattle against respiratory and reproductive disease with modified live virus (MLV) BVD and IBR vaccines is 30 d prior to the onset of the breeding season (Stormshak et al., 1997). Pre-breeding vaccination is practiced to protect both cows and calves against respiratory antigens, protect the fetus against infection, and reduce economic losses associated with diseases. When compared to killed viral product vaccines, MLV vaccines are typically accepted to stimulate adequate immunity without requiring a second inoculating dose. However, the use of MLV vaccines have been reported to result in decreased conception rates, congenital anomalies, or abortion of pregnant animals. Estrous synchronization reduces the labor necessary to implement an effective artificial insemination protocols in beef cattle. Programs that decrease or eliminate heat detection (Fixed-time artificial insemination) are increasingly used in beef cattle to achieve pregnancies. In order to vaccinate cattle with a MLV vaccine 30 d prior to synchronization, animals must be handled at least one additional time. Concurrent vaccination at the initiation of an estrous synchronization protocol has the potential to reduce the labor efforts associated with these two managerial herd practices. Conversely, if vaccination with ML V BVD and IBR antigens at the start of estrus synchronization results in significantly lower pregnancy rate, cattlemen should avoid this management practice.