Avalon Animal Clinic Animal health matters: Isolating, testing new animals can prevent big headaches

Animal health matters: Isolating, testing new animals can prevent big headaches

Most livestock producers probably think of swine or poultry-raising operations when the term “biosecurity” gets mentioned. Over the years, those operations have refined their methods for keeping new diseases out of their animals. The stakes are high. New infectious diseases aren’t just nuisances; the resulting illnesses and death losses can mean financial ruin.

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Accordingly, swine and poultry producers pay close attention to how workers, vehicles and equipment make contact with their farms and animals. They also worry about wildlife, rodents, contaminated feed and — holy cow! — trucks driving by on adjacent roads or viruses traveling on wind currents. Porcine Epidemic Diarrhea (PED) in pigs and avian influenza in poultry are viruses that managed to evade previous biosecurity measures, going on to devastate animal groups.

These methods can be contrasted with the world of cow-calf production. What are normal operating procedures on cow-calf operations would make a pork producer shudder in horror. People, trucks and ATVs move freely between animal groups and farms with no concern about manure on boots or truck tires. Wildlife and rodents occupy the same outdoor spaces as the cattle.

It’s not that cattle producers are lazy or feel disease prevention is unimportant; it has more to do with diseases behaving differently in different species. You don’t hear much about deadly viruses sweeping through cow-calf operations. Why is that? Maybe cattle are comparatively a little tougher in terms of immunity. The space required to raise cattle might make it harder for viruses to jump between animals.

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Yet devastating diseases can affect cow-calf herds, too. They’re just not as swift and dramatic as the swine and poultry diseases I’ve mentioned. But given free rein and enough time, problems like Bovine Viral Diarrhea (BVD), Johne’s Disease or calf scours can torpedo a herd’s productivity. Despite this, visitor and traffic restrictions aren’t common components of cow-calf herd management. Effective biosecurity programs for these operations should consider these routes of pathogen entry — but how new cattle enter a herd is much more important.

Compared to their presence on a dirty pair of boots or ATV tires, viruses and bacteria thrive and multiply in cattle, making those animals everyday reservoirs of these germs. Excluding visibly sick new cattle from a herd is necessary but not sufficient: germs such as BVD or the bacteria causing Johne’s Disease often come in with outwardly healthy animals.

Isolation and disease testing are the two main ways to reduce the risk of newly purchased bulls, heifers or calves becoming disease sources for the main herd. They’re not perfect, but when implemented properly, they’ll reduce the vast proportion of the risk.

Isolation means keeping new animals separate from the rest of the herd long enough — 30 to 60 days — for most of the germs they’re shedding to drop to a low level, or for the animals to get over any illness developed from the stress of moving to a new home. This applies to any new arrival, including bulls, open heifers, bred heifers or cows, and — for adventurous producers — foster calves (isolated with their new mother away from the rest of the herd).

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A 60-day isolation period seems like forever, but for some persistent forms of cattle disease, it’s not near long enough. Cattle persistently infected with BVD virus are an example, serving as overwhelming, relentless sources of virus for their herdmates. Here’s where the second tool — diagnostic testing — plays a role. A small ear notch can be tested to detect persistent BVD infections.

All new arrivals should get ear-notched for BVD, with two exceptions — pregnant heifers and cows entering a herd. The fetus they’re gestating could be persistently infected while they themselves are not. These females should be isolated until they calve and the newborn calf can be tested. I know of instances of BVD entering a herd through bred animals that weren’t handled as such.

Unfortunately, not every disease can be halted through these efforts: Johne’s Disease is an example. Even if they’re infected, young animals won’t test positive until months or years later — close to the time when they’ll start to show signs of illness. For this disease, another component of biosecurity — that of knowing the health status of the source herd — becomes critical.

Biosecurity programs should be implemented with advice from a veterinarian. Put together, isolation and testing can meaningfully reduce the risk of new animals bringing big headaches with them to their new home.

Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University. He can be reached here via e-mail at [email protected] or at 605-688-5171.