For cow-calf operations, herd health begins with a biosecurity program. But for most, implementing a plan means finding a balance between the ideal and the practical.
Any time you introduce new animals to a herd, there is a chance they could be carrying disease agents or actually suffering from a disease, says Dale Grotelueschen, a managing veterinarian with Pfizer Animal Health’s Beef Cattle Technical Services. Keeping disease agents out of the herd should be a central part of a herd-health plan, as reducing disease exposure is an ideal way to prevent disease and improve outcomes.
Some diseases of concern when introducing animals include bovine viral diarrhea, anaplasmosis, trichomoniasis and Johne’s disease, as well as some parasites.
The pathway of disease infection can go two ways when ranchers introduce new animals to a herd, Grotelueschen says. The new cattle can bring pathogens for which the resident herd has little resistance, or the new animals could be susceptible to pathogens present on the ranch for which the resident herd has built a tolerance.
A question for producers, though, is just how much time, labor and expense to invest in biosecurity, based on the value of cattle, risk of disease and other considerations.
Veterinarians recommend, for example, testing and isolation of purchased cattle to prevent introducing BVD in beef herds. As a general rule for preventing introduction of BVD and other diseases, Grotelueschen says to isolate new arrivals for at least three weeks if possible. This allows time for testing and vaccinations, and for the animals to show signs of other disease such as respiratory viruses or anaplasmosis. If problems arise, the buyer can extend the quarantine period as needed.
Texas A&M University Extension veterinarian Tom Hairgrove agrees, saying anytime you bring in replacement females, BVD testing is a high priority. “We recommend purchasing only females verified negative for BVD through earnotch testing. However, producers do not always understand that bred females, even those with a negative test result, could deliver a persistently infected calf that will cause a wreck.”
Cows exposed to BVD during gestation can pass the virus on to their calves. The cow can recover quickly and test negative for the disease, but the calf could be born with a persistent infection. Some of these PI calves die shortly after birth, but others can appear healthy while spreading the virus throughout the herd. Test these calves as soon as possible after birth, Hairgrove says. Do not wait until weaning, as a PI calf could infect much of the calf crop during that period. “Testing calves from all purchased females for BVD is a critical component of a biosecurity plan,” Grotelueschen adds.