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.
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.
Seedstock producer Bill Rishel of Rishel Angus, North Platte, Neb., says he tests all purchased cattle, and the bulls he sells, for BVD. He also vaccinates all females and calves for BVD. He has never found a cow with BVD or a PI calf but continues a strict vaccination and testing protocol to minimize risk.
For commercial producers, though, Rishel acknowledges that testing all purchased cattle for BVD might be too expensive or impractical. His bulls, like those from many seedstock producers, are tested and marketed as BVD-free.
But as producers buy larger lots of heifers, cows or pairs, he believes a sound vaccination program could be the most practical approach.
As for isolating new cattle, Rishel says while it might be the safest strategy, it is impractical for many ranchers. So again, he stresses the need to work with a veterinarian to assess risk and implement a health protocol that achieves a balance between the ideal and the practical.
Assess the risk of importing disease
With a focus on practicality, Rishel stresses that the foundation of a biosecurity and herd-health program is a sound relationship with a veterinarian, and says his veterinarian, Kevin Albertson of Stockman’s Vet Clinic in North Platte, plays a key role in his herd-health planning.
Part of the value of that relationship is that the veterinarian can help evaluate the level of disease risk imported cattle present, based on their source, history, ranch location, time of year and other factors.
Rishel says that as cow-calf producers purchase more cattle over the next few years as they expand or rebuild their herds, they should learn as much as possible about the source. When possible, he says, inquire about the seller’s herd-health program and relationship with a veterinarian, and the health and vaccination history of the cattle.
In some cases, of course, that information is lacking, but whether the purchased cattle come with volumes of health records or none at all, the buyer’s veterinarian can help design receiving and vaccination protocols to minimize the risk of introducing disease to the herd.
Timing of introduction can influence risk. Introducing new animals into herds around calving time, for example, increases the risk of calf scours, Grotelueschen says. Hairgrove points out that grafting calves from other herds or bringing in lactating females to graft calves introduces considerable risk. Any females introduced for this purpose should be managed in isolation from the rest of the herd.
Consultation with a veterinarian also helps producers make decisions based on regional or local prevalence of a disease. For example, Hairgrove notes that in Texas diagnostic testing has shown anaplasmosis is prevalent in some areas and absent in others. Cows native to infected areas get along fine, but cattle shipped into those areas could suffer losses due to lack of tolerance to the disease. Likewise, cows shipped from infected areas could introduce the disease to other herds where tolerance is low. If you are in a “naïve” area, you might want to test incoming cattle, Hairgrove says.
He also notes that sanitation is a component of biosecurity. Animal vectors such as biting fl ies and ticks can spread anaplasmosis, but Hairgrove says poor sanitation of tagging tools, needles or dehorning tools commonly results in transfer of the pathogen through blood.
Trichomoniasis has become a growing concern as the sexually transmitted disease can cause disastrous losses in cow-calf herds due to abortions. While several states require testing of non-virgin bulls for interstate sale, Grotelueschen suggests considering testing bulls even where not required to protect herd health.
Hairgrove warns that hidden trichomoniasis infections in purchased cattle can cause problems down the road. An infected gestating cow, for example, purchased earlier than
five months into gestation, could abort a calf, then re-breed. The producer might be unaware of the abortion, but the cow carries the disease over to the next breeding season, potentially passing the disease on to bulls, which then infect additional cows. Hairgrove recommends that any females purchased at 150 days or fewer of gestation should be managed separately from the rest of the herd. The test for trichomoniasis is about 85 to 90 percent accurate, he says, which is good, but one in 10 bulls could carry the disease in spite of a negative test result.
Rishel voluntarily tests all bulls for BVD as a service to customers and also tests for trichomoniasis based on each bull’s destination. Some states require testing for certain classes of bulls, but state regulations vary widely, creating a challenge in determining which bulls need the expensive test. Some states, for example, require testing only for nonvirgin bulls imported into the state. Others require testing of all bulls over a certain age, such as 18 or 24 months, and some require testing of all bulls at transfer of ownership. So, Rishel says, seedstock producers delay testing until after bulls are sold and determine the need based on the buyer’s home state.
Hairgrove also sees parasites as a biosecurity issue, in the case of either exotic or common parasites. Parasites typically do not cause much clinical disease or death loss, but economic losses due to reduced performance or reproduction can be significant.
Parasites common to some areas could create problems as cattle are shipped into new areas. Already, Hairgrove says, researchers in Texas are conducting tests to help predict what types of parasite populations might emerge in the state once producers begin re-stocking their ranches with cattle from other parts of the country.
In addition, Hairgrove notes concern over the possible emergence of resistance to deworming products among some worm populations. Debate on this issue continues, but producers eventually could risk importing resistant parasites with purchased cattle, resulting in loss of effectiveness of their parasite-control programs. Meanwhile, Hairgrove recommends deworming new cattle upon arrival and isolating them to avoid introducing parasites to pastures.
Lock out BVD
Among the diseases potentially introduced when importing cattle, bovine viral diarrhea is one of the most dangerous. NCBA’s BVD working group and the Academy of Consulting Veterinarians have teamed up with the Beef Cattle Institute at Kansas State University to help producers develop realistic BVD-control plans that fi t individual goals and management constraints.
The group recommends these steps to develop a plan for BVD control and eradication:
1. Meet with your veterinarian to determine or review your BVD goals and current exposure risk. Introduce only PI-negative animals into the herd. Calves from purchased pregnant females must test negative before the pair is added to the resident herd.
2. A number of tests for PI cattle are available; work with your veterinarian and diagnostic laboratory to determine the best testing strategy for your situation. Options include:
• Prior to the start of the breeding season, test all calves and all non-pregnant females without calves, including those that aborted, were never confirmed pregnant or lost a calf for any reason, that have not been tested previously.
• Isolate pregnant females until they calve and their calves can be tested.
• Some herds may require annual calf testing.
• Prior to the start of the breeding season, test all bulls and replacement females (home raised or purchased) that have not been tested previously for PI status.
• Maintain documentation of test results.
3. Work with your veterinarian to design a vaccination program that considers vaccine type and timing. This includes considerations of bull turn-out, pre-weaning, weaning, heifer pre-breeding, and mature-cow vaccination to optimize fetal protection.
4. Work with your veterinarian, neighbors and replacement suppliers to identify and minimize risk of introducing BVD to your operation.
Learn more from the group’s online BVD resource page at bvdinfo.org.
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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.
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