Johne’s disease in cattle results in potentially big financial impacts for producersWritten by Heather Smith Thomas
Johne’s is a sneaky disease that producers probably won’t notice until it is already well established in a herd. It doesn’t show up until an animal has been infected a long time – and eventually shows signs of illness, like diarrhea and weight loss.
For many years, beef producers were unaware of this disease or thought it was present only in dairy cows. Nearly 70 percent of beef producers surveyed in 1997 by the National Animal Health Monitoring System had no idea what it was. About 23 percent had heard of it, but only 2.4 percent were knowledgeable about Johne’s disease.
This information gap is changing, but the industry is still a long way from having a handle on this devastating disease.
Allen Roussel of the Department of Large Animal Clinical Sciences at Texas A&M University and a team of researchers looked at the effect of Johne’s on weaning weights in beef herds, comparing calves from dams testing positive for Johne’s with calves from uninfected cows.
“This study was funded by USDA. We used data from the U.S. National Johne’s Disease Demonstration Herd Project, which compiled data over a period of about six years. These demonstration herds were located in 18 states,” says Roussel.
The study looked at differences in 205-day adjusted weaning weights of calves from cows that tested positive in fecal cultures and cows with a strong positive serum ELISA blood test, compared with calves from test-negative cows in those herds.
“Weights were around 60 pounds and 50 pounds less, respectively. This is a substantial loss in calves from cows that are either shedding bacteria in feces or positive on the blood test. These are cows in late stages of infection and dropping off in milk production even though they may not have diarrhea or substantial weight loss, yet. They are being affected, even though they may not look sick,” explains Roussel.
“To put this into perspective, we find a lot of beef herds with a low prevalence of Johne’s, much lower than we find in dairy cattle, which are generally more confined. I have spoken with beef producers and veterinarians in the Midwest who concentrate their herds at calving time because they calve early, and some of these herds have high prevalence also,” Roussel comments. “But here in Texas where most cattle are out on pasture year-round, they tend to have low prevalence.”
In western states many herds are confined at calving so they can be calved and bred early before they go to summer range.
“I talked to a veterinarian in Montana who had a client with a substantial problem. There may be some herds with higher prevalence in northern states where cattle are confined for early calving. Most of the southern cattle are more spread out,” he says.
“If a herd has a high prevalence, there are more calves weaning light. If a producer has a low prevalence, there are only a few calves weaning light. The economic significance is much less, and producers have to think about how much they can afford to pay for testing and control within the herd,” says Roussel.
“From a national herd basis, there are probably fewer than 20 percent of beef herds infected. Thus, the most important thing in a control program is to not get infected by taking biosecurity precautions to not introduce animals that might pose a potential risk,” Roussel explains.
“Since many of the cattle coming into various herds are purebred bulls, it is important that the purebred industry control it within their herds. Internal control and testing is probably more important for them, partly because the animals are more valuable,” he adds. “They are not worried about losing 60 pounds at weaning. They are worried about losing a very valuable animal prematurely or selling one to somebody and dealing with those consequences.”
A seedstock producer doesn’t want to send this problem to customers’ herds.
“From the commercial standpoint, in beef cattle that are spread out in large pastures, Johne’s disease does not have as much economic importance. In purebred cattle, and in any herds that are more intensively managed, it certainly can have economic implications,” says Roussel.
Some of the traditional things stockmen have done, without thinking about possible consequences, can put their herds at risk, such as getting colostrum from a dairy, bringing home a dairy calf to graft onto a beef cow that lost her calf or buying an older cow from a dairy to use as a nurse cow to raise orphan calves.
The biosecurity risks include not only Johne’s disease but also diseases like salmonella, cryptosporidiosis, leukosis and other diseases that they may not have in their beef herd.
“For a long time people in the beef industry were using Holsteins as embryo transfer recipients, but they are now using beef cows instead because of the risks. Johne’s can be passed from an infected dam to the fetus before birth and through milk and colostrum to the calf,” he explains.
“One of the things we emphasize when talking to producers about control measures other than testing is to look at practices that have multiple benefits,” Roussel says.
He adds that producers can do many things to reduce the prevalence of Johne’s, but they also have other benefits, like minimizing the spread of calfhood diarrhea and many other diseases.
“Johne’s is fecal-orally transmitted,” he says. “When we spread out the cattle and their manure and reduce contamination of the environment, we not only minimize the spread of Johne’s disease but also help prevent other problems.”
It also pays to make sure sources of any new cattle, including bulls, are free of diseases. It may not be enough to go by a breeder’s reputation as a good seedstock producer.
“Just because a producers always buys bulls from X ranch and they are really nice people with a good reputation doesn’t mean they don’t have to worry about Johne’s. I don’t think anyone intentionally sells infected cattle to someone else. Many times they simply don’t know they have Johne’s disease,” he says.
Without testing, producers may not know. This disease may have slipped into their herd without their knowledge.