WIDESPREAD PROBLEM Up to three-quarters of Alberta dairy herds may have animals carrying the mycobacterium that causes Johne’s
Why wouldn’t you participate in a program that is free, and benefits both your cattle and the dairy industry?
More than half of western Canadian cattle operations, beef and dairy, have animals infected with the mycobacterium that causes Johne’s disease. That prompted the creation of the Alberta Johne’s Disease Initiative in 2010. The free program is co-ordinated by the U of C veterinary faculty, endorsed by Alberta Milk producers and has funding from the Alberta Livestock and Meat Agency.
It’s estimated between 40 and 74 per cent of dairy herds in Alberta are infected, infectious disease expert Herman Barkema told attendees at the recent Western Canadian Dairy Conference.
But so far, only 38 per cent of producers have signed up for the program, which is centred around both testing and education.
“Our goal is to have 80 per cent of the dairy producers in the province enrolled in the program by the end of this year,” said Barkema, a professor in epidemiology of infectious disease in the faculty of veterinary medicine at the University of Calgary.
“We really want to go to 80 per cent. If you want to control an infectious disease like this one, you need the majority of the herds to participate. We want to show consumers that we care so we want a really high participation rate.”
Johne’s is caused by mycobacterium avium subspecies paratuberculosis known as MAP, an organism related to the bacteria that causes tuberculosis in people.
“This was the reason we started pasteurizing our milk in the 1920s,” Barkema said.
MAP grows very slowly and takes a long time to culture. However, that’s changing. It shows the same growth in about 49 days today that used to take about half a year a decade ago. Johne’s infects the intestines of ruminants including cattle, sheep and goats.
“Every country that has dairy or beef cattle has Johne’s disease, or has seen it,” Barkema said.
“Typically you would have a low infection rate. It takes a long time for the infection and then the inflammation to build up.”
Johne’s disease may have a possible link with Crohn’s disease, an inflammatory bowel disease that affects humans. Evidence of the disease will only show up in the manure of infected cattle over the age of six, so most dairy cows are culled before they display clinical symptoms. The disease is transmitted to calves through manure ingested orally. Beef cattle have lower infection rates of Johne’s than dairy cattle, although researchers don’t know why.
The disease can have a severe economic impact, with some herds having a cull rate six times higher than non-infected herds.
“These animals just don’t take enough energy and protein in,” said Barkema. “They don’t grow well enough, have a negative balance and they just don’t get pregnant. If they do get pregnant and calve, their production is way lower than that of other animals.”
A quarter of the herds that participated in the program so far have tested positive for Johne’s, with large herds having more positive tests. All cattle veterinarians in Alberta are trained to administer the program, which starts with an initial risk assessment followed by a plan to improve herd health.
“These can be simple measures, like rinsing off boots before going to the calves,” said Barkema.
Environmental samples are also taken in different areas of the farm and it’s been found that infected manure is more often located in areas such as lagoons and alleys.
Nearly two-thirds of the operations participating in the program needed stronger biosecurity protocols.
“Anyone with dirty boots could walk in and just go to the cows,” Barkema said. “We like to be nice, but we don’t like people to bring things on to our farm. I don’t understand why farmers don’t have boots and coveralls for visitors.”
More than 50 per cent of the herds surveyed fed calves from pooled milk of several cows, which can spread infection among the herd, said Barkema. All the participating herds should do a second risk assessment a year after joining the program, he said.