FIRST, the good news about bovine Johne’s disease (BJD). Despite it having been present in Australia for at least a century and despite it being common in some dairy regions, BJD remains rare in beef herds.
However, the bad news is that BJD is an insidious disease that can arrive on a farm in an apparently healthy but infected animal.
It causes cattle, normally in middle age, to develop persistent ‘pea soup’ diarrhoea and lose weight until they become emaciated, then die. Once on the property the disease is difficult to eradicate in part because it survives in the soil for up to a year.
BJD is also difficult to eradicate because while tests are okay at the herd level, the tests are not accurate for individual animals.
Therefore, we cannot test a herd and advise which animals are infected and which are free of the disease.
A drastic option if the farmer decides to eradicate BJD is to destock breeding cows for 12 months. We have a few other options but I mention this to emphasise the point that cattle producers do need to take BJD seriously.
My fellow district veterinarians would also like cattle producers to understand the consequences of BJD because for some of us, this disease consumes an inordinate amount of our time.
How can we justify this for a disease that is rare and of relatively little consequence at least for the beef industry?
The reason we spend a disproportionate amount of our time working to control a disease that kills less beef cattle than lightning strike is because there are a couple of elephants in the room in regards BJD.
Some countries are working hard to eradicate BJD and when they do, may impose trade barriers on those that still have the disease.
The most important is Japan, still our most valuable beef market.
We consider that BJD had the potential to become a major issue in the future.
Which brings me to the question, what is the most important thing beef cattle producers need to know about BJD?
The answer is that BJD is approximately 100 times more common in NSW dairy cattle than NSW beef cattle and so dairy cattle represent a significant risk.
If you are a specialist beef cattle producer considering the future and wishing to sell livestock to the widest range of markets, from quality restockers both in NSW and Queensland, to export beef (in the future) you need to ensure that you do not run or agist dairy cattle on your beef property.
It is easy to determine that a large lean cow with black and white spots or a small yellowish cow with dark points and baby seal eyes is a dairy cow and therefore poses a higher risk of BJD.
However, Angus bulls, widely used over heifers in the dairy industry, produce progeny that are both productive beef animals and are almost indistinguishable from straight bred beef cattle.
Fortunately, the steer progeny from the dairy industry, because they are usually sold before two years of age and therefore before any BJD infected animals start shedding the bacteria, are considered a low risk.
However, if the female progeny were kept as breeders, the risk increases markedly.
Our message to beef cattle producers is clear.
To reduce the risk of BJD, only buy cattle from and agist cattle on properties that have only run a beef herd using traditional beef animals. To ensure this, request a cattle health statement where the vendor tells you about the background of the animals.