As spring rains and green grass offer producers the hope of restocking their pastures, it’s important that they have a solid reintroduction plan to reduce disease risk in the cow herd, says Dr. Mac Devin, Senior Professional Services Veterinarian with Boehringer Ingelheim Vetmedica, Inc.
“Producers need to visit with their veterinarian to make sure they are doing everything they can to reduce disease challenges,” adds Dr. Devin. “If you still have cattle on your place, and are expanding cow numbers, you need to have a plan to isolate the new animals to protect both groups of cattle.”
He recommends 30 to 45 days of isolation before commingling purchased cattle with the resident herd.
“There needs to be separation so there is no nose-to-nose contact,” Dr. Devin says. “Each new group of animals needs to be isolated to allow for incubation of infectious disease, if they have been exposed. If an animal is going to show sickness, for most infectious disease it will be during the first 30 to 45 days.”
Over time, cattle that remain in a particular population, location or environment become resistant to the disease-causing organisms or parasites present there. As an example, Dr. Devin explains that anaplasmosis is endemic to many areas of Texas.
Cattle in those areas have developed some resistance to the tick-borne disease; however, cattle that are brought in that are naïve to anaplasmosis, may become infected when exposed. This may result in adult cow losses or abortion.
“Sometimes, the cost for developing this resistance is reproductive or production loss,” continues Dr. Devin. “We use vaccines and other measures to minimize these losses.”
As an example, leptospirosis is potentially present in animal reservoirs (feral hogs, deer, coyotes, skunks, opposums and others) in most of Texas. Because the wild animals share the environment with the cattle, there is good potential for exposure.
If introduced animals are not adequately vaccinated, one exposed animal in the group may amplify the exposure to others, with the result being significant pregnancy loss. Leptospira prefer warmer climates, so Northern cattle may have limited naturally acquired immunity to lepto. Therefore, vaccination following label directions is important.
Another example that Dr. Devin shares is related to strains of bovine viral diarrhea (BVD) that are in an area. In populations, one particular BVD strain or subspecies may predominate in one area, and a completely different one may predominate in another area.
If these two strains are far enough apart immunologically, when one population of animals is moved into another area, it may have minimal resistance to the new strain of BVD.
Because abortion due to BVD can occur at any stage of pregnancy, cows need to be adequately vaccinated before being exposed to the new area. Dr. Devin also reminds producers that it is important to read and follow label directions.
Finally, Dr. Devin recommends that producers looking at restocking work with their local veterinarian to carefully assess risk for disease-related losses and develop plans to minimize that risk. Those plans may include preventive measures such as vaccination and careful selection of the age/reproductive status of animals to be introduced.
For more information on a preventive approach to animal health, visit www.BIVIPreventionWorks.com. 
—From Boehringer Ingelheim Vetmedica
