Timing of Reproductive Vaccinations in Beef Cattle Herds

Infectious reproductive diseases have great potential to create significant damage to reproductive efficiency and therefore profitability for the beef herd. Pathogens causing reproductive diseases include: bovine viral diarrhea (BVD), infectious bovine rhinotracheitis (IBR), Leptospira, Tritrichomonas foetus, Campylobacter fetus subsp. venerealis (“vibrio”) and Neospora caninum, among others. Management practices to prevent or control infectious disease should consist of efforts directed towards biosecurity (keeping sources of new diseases out of the herd), environmental control (reducing stress and conditions in which infectious diseases may be transmitted), and vaccination. Vaccination has long been employed as a means to increase the resistance of individuals, thereby the group, to infectious agents. For reproductive diseases, the goal is to increase resistance of the female (or bull) toward agents that will adversely affect the female’s ability to carry a pregnancy to term; the hopeful result of which is a healthy, viable calf. The focus of many reproductive vaccine programs is on preventing abortions, but attention should also be paid to diseases that have an effect on ovulation rates, fertilization rates, embryonic survival rates, and perinatal survival rates. Many agents of reproductive diseases will have effects on several, if not all, of these stages of reproduction. In most cases in which vaccine is used as a management tool to lower the risks or effects of disease, the focus is on protecting the individual animal from illnesses that have an economic effect. For reproductive diseases, this focus shifts to protecting the pregnancy. In mature cattle, most agents of reproductive disease will cause very little to no clinical illness in the cow, yet may easily infect the reproductive tract or developing fetus such that infertility is the result. For example, an exposure of a pregnant cow to a relatively moderate amount of BVD virus may result in no outward signs of illness in the cow, yet be enough to cross the placenta and infect the developing fetus, with several potential deleterious outcomes (Ficken et al., 2006) Reproductive diseases for which vaccines are widely used and available have been described in the previous paper. With the possible exception of Neospora caninum, all of these agents have been implicated in failure to conceive or early embryonic death, resulting in open cows at pregnancy examination. Therefore, a reproductive vaccine program should be designed to confer high levels of immunity at the time of breeding and in early gestation. Because most vaccines take two to four weeks to reach peak effect, vaccination should be performed well before breeding time, optimally 28–30 days prebreeding.