Animal Health Matters: What else are you taking home from the bull sale?

Russ Daly
Special to the Farm Forum
Russ Daly

It’s bull sale time!

For seedstock producers, this time of year is their Black Friday – plus a chance to show off their herds and reconnect with customers and friends.

Bull buyers also look forward to the chance to connect with others in the industry and visit different operations, but the opportunity to improve their herd genetics is their first priority. Their goal is to bring home better bulls than those they’re replacing.

Sale bulls on display are the picture of health and vitality – the best the seedstock operator has to offer. Health, or lack of disease, is taken for granted. It’s a rare bull sale ad that even mentions anything about their animals’ or herd’s health status. Therefore, it’s counterintuitive to consider these animals a potential source of disease for the herds they go home to.

I’ll grant that purchased bulls bringing in an infectious disease doesn’t happen that often. But pinning a definite cause of an outbreak to a bull (or group of them) is difficult. For many herds, though, the list of potential disease sources starts and stops with the bulls – often the only animals brought in from outside.

When I get calls from producers suspecting they brought in a disease through a bull, it usually involves one frustrating disease: Johne’s disease. Animals with Johne’s disease don’t come out of it. It’s a slowly progressing bacterial disease of the gut that results in chronic diarrhea and progressive wasting even while the animal continues to eat. Fortunately, in our beef herds, Johne’s tends to be a low-incidence disease. But unchecked, it can slowly but exponentially spread through a herd to cause real economic loss.

Frustration over Johne’s disease stems from the biology of the disease itself: in particular, the incubation period. It can be years from the time a susceptible animal, usually a calf, is infected with the bacteria to the time when the disease becomes obvious in that animal. This makes it really tough to single out the particular instance when the infection entered the herd, let alone which animals brought it in. For many animal diseases, I can help producers figure out the entry event by looking back at what happened two or three weeks ago. What happened two or three years ago (or more) is a lot tougher to identify.

This years-long incubation period is frustrating for the seedstock producer, too. Since this long time period also applies to the length of time for an animal’s blood or manure test to show positive after infection, their ability to identify any potentially infected animals in a timely manner is limited. A negative test on a yearling bull really doesn’t mean anything. Even if he’s infected, his blood or manure test won’t show it until a few years down the road.

So what’s a bull buyer (or seller) to do regarding Johne’s disease?

While tests on individual bulls aren’t valuable for the reasons mentioned above, whole-herd tests do have merit. Testing older animals within a herd, especially if done annually, will identify infected animals that can be removed before they infect more animals (especially calves within the herd, which are more susceptible).

The state, using federal guidelines, has a program in which herds undergoing Johne’s testing can become classified as tested at certain levels. The requirements are fairly extensive, but I’d bet there are some herds already doing a level of Johne’s testing that would qualify them for certification.

For seedstock operators, having a Johne’s classified herd would demonstrate to buyers that their risk of bringing Johne’s disease home with a bull or heifer is low .

Unfortunately, officially classified herds are relatively uncommon, so it’s largely up to buyers to determine the risk level of the herds they buy bulls from. A good start is a conversation with the seedstock supplier. Do they test their herd for Johne’s disease? If so, how often? Have they found infected animals and removed them? In my mind, a herd that routinely tests – even if they’ve found some infected animals in the past -- is more trustworthy than one that’s dismissive of or unaware of the disease.

Rightfully, decisions about the genetic worth of the bulls you purchase should be at the top of your mind this bull-buying season. But keep these health questions in mind, too. It could prevent some potential headaches years down the road.

Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University.  He can be reached via e-mail at russell.daly@sdstate.edu or at 605-688-5171.