New calculator to help analyze Johne’s test options

With no treatment or vaccine available, the impact of Johne’s disease on cattle herds can be a nightmare.

“Johne’s disease is especially difficult to manage because we have so few options,” says Dr. Cheryl Waldner, a professor at the Western College of Veterinary Medicine at the University of Saskatchewan.

To help beef producers make better management decisions regarding such an uncertain disease, the Beef Cattle Research Council (BCRC) is launching an interactive tool to analyze Johne’s disease testing and management options. Waldner helped develop the new tool.

This chronic disease causes weight loss, persistent diarrhea and death in cattle, with many negative effects on beef herds. In addition to premature slaughter, these effects can include reduced slaughter value, replacement costs, loss of calf gain, loss of genetics, and considerable veterinary testing costs.

Since calves under six months of age are more susceptible to Johne’s disease, efforts to reduce the spread of infection to calving areas – similar to those used to reduce calf scours – can help manage the disease. However, as the beef industry consolidates, the risk of Johne entering a herd through new animals is worth watching.

“The only way to find and get rid of these infected animals so they don’t get passed on to our calf production is to test and cull, and that sounds simple enough, but it’s not. This particular disease is very frustrating because it has a long silent phase,” says Waldner. It can take two to ten years from when an animal is infected to when it shows clinical signs, she adds.

Even when animals shed virus, it can be inconsistent and not show up in tests. In addition, the accuracy of the available tests is limited.

“There’s a lot of uncertainty around this, and because of that, it’s very difficult for producers and veterinarians to try to assess the profitability possibilities of a test and cull program in their herd. There’s a lot of information to gather, and it’s easier if we can get the computer to do it for us.

This new risk-reward calculator for Johne’s disease “brings together what we know about the disease, how it might progress in individual animals, how it might spread in the herd, and how well diagnostic tests work in animals.” Canadian beef cattle herds,” says Waldner.

“The tool can be customized to accommodate herd sizes, replacement strategies, expansion plans, and a wide range of possible testing possibilities.”

Two versions of the calculator, basic and advanced, will be available on the BCRC website. Instead of running the model once and displaying a scenario, the tool runs it multiple times and takes into account the uncertainties presented by this disease to provide growers with a range of possible management scenarios.

“It’s a bit more complicated than a lot of the Excel tools that we typically use for these types of calculations, but given the level of uncertainty, we needed something that allowed us to account for that uncertainty in the calculations. calculations.”

A key part of developing this tool was to incorporate data from Canadian herds into the risk model. “The important thing for us was that this tool reflected data from western Canadian cow-calf herds,” says Waldner, noting that much of the existing research on the spread of this disease has been conducted in American dairy herds and is not useful in this particular context.

The Canadian Cow-Calf Surveillance Network provided some of the data used to create the model. “We have data from herds across Canada that not only tells us how many Johne’s are in herds right now and what is the variation between herds in terms of how much Johne’s they have if they have any , but also we were able to do a study that looked at how the tools actually work in our herds,” she explains.

While determining how quickly the disease spreads through a herd is difficult, data collected by the Saskatchewan Stock Growers’ Association on this specific topic helped inform the calculator’s model. The association has worked with producers who have dealt with Johne’s disease to help track the progress of the disease in their herds, and many producers have shared their data anonymously with the project developers.

“With this, we were able to use the model to help us guess how the disease actually progresses in beef cattle herds and use that as the basis for our predictions in terms of what happens over a 10-year period. “

Waldner notes that the tool can’t predict exactly what will happen in a herd, but it does provide producers with scenarios to analyze that can help inform their management decisions.

“What I hope is that individuals will be able to make better decisions about whether it makes sense to test in their herds and come up with a testing protocol that makes the most sense to them. “

The Government of Saskatchewan, the Saskatchewan Cattlemen’s Association and the Alberta Beef Producers also funded the development of this calculator.

Eleanor C. William