Prebreeding vaccinations should be completed ~4 wk before the start of breeding and should be based on local patterns of disease and state and national requirements. Replacement females should be vaccinated with the same vaccines given to mature females before breeding.
Precalving vaccinations are intended to protect the newborn calf through colostral transfer. The most common immunizations are those that offer protection against some of the infectious causes of diarrhea in neonatal calves. Others are based on local patterns of disease. Many of these vaccines have variable results when used in field conditions and should not be used in substitution of excellent management practices.
Preweaning is an important intervention that can help prepare calves for the stress of weaning and reduce the possibility that such stress will compromise the efficacy of biologicals. Common vaccinations include those against the clostridials and bovine respiratory disease complex (BRD). A broad-spectrum anthelmintic should also be given at this time, because calves that have been on pasture have almost certainly been exposed to internal parasites. At weaning, a second vaccination should be given for those products recommending two injections. Modified-live virus (MLV) products should be given at this stage. Another clostridial vaccination is not indicated if calves were previously vaccinated at working and preweaning. For areas where brucellosis is under regulatory control, heifers should be vaccinated appropriately within the age ranges stipulated.
Bulls should receive the same vaccines as the cow-calf herd, with some exceptions. Bulls should not be vaccinated for brucellosis. Also, the trichomoniasis vaccine currently approved for use in the USA is not approved for bulls. Caution is advised with MLV infectious bovine rhinotracheitis vaccines, because this virus may recrudesce in bulls and be shed in semen; the manufacturer’s technical services veterinarian should always be asked if this is a concern. Also, if MLV infectious bovine rhinotracheitis vaccine is used, semen shipment to other countries may be jeopardized.