A federal research scientist has developed “a hint of a tool” for predicting roundworm risk in Alberta pastures.
“The question we came up with late at night was: Can we make a correlation between egg counts, antibody levels, and environmental parameters and build a GIS map that would give us an idea of what the epidemiology is in various parts of Alberta?” said Doug Colwell.
It took three years to develop, but by using GIS (geographic information systems) mapping and standard methods for detecting roundworms, Colwell and his team created a system to forecast where infestations are likely to occur.
“There’s a number of different ways to detect nematode parasites,” he said.
Antibodies in the blood are “particularly indicative” of problems in calves being put out on pasture for the first time.
“Calves undergoing their first exposure develop antibodies fairly quickly,” said Colwell. “It’s pretty clear that more worms equal higher antibodies.”
Colwell collected blood and fecal samples from calves in 20 auction marts across the province and ran tests for antibodies in the blood and egg counts in the feces.
Those results were then layered onto a GIS map that showed the location and likely catchment area of each auction mart.
“If you put the road map in along with the auction mart locations, you can develop a polygon around each of the auction markets, which is the most likely place these animals came from,” he said. “The assumption was that producers are not going to drive their cattle a long way to get them to the auction mart.”
Meteorological data from provincial government weather stations was then added to the map to create “risk categories” for the calves.
“It’s really well established that eggs and larvae development are influenced by environmental conditions,” said Colwell. “Moisture is one of those key conditions.”
The result was three parameters — growing-degree days above 5 C, precipitation, and extended periods of cool weather — that could be used to calculate risk.
“Temperatures are the ones that seem to drive the higher levels. It’s not very surprising that the southeast of the province generally has low risk. Up around Grande Prairie, it’s relatively low risk as well.”
And although antibody levels correlated “very nicely” with those three weather factors, fecal egg counts didn’t correlate at all.
“Generally speaking, the results of the study show that a lot more calves are exposed to nematodes than is picked up in their fecal matter,” he said. “Fecal egg counts don’t necessarily mean a great deal.”
Given that, the findings seem to support the approach used in most production systems in Alberta, namely “that all calves get treated all the time.”
“There is a group of calves out there that has very high levels of antibodies, and if you were basically to target a treatment program, those are the ones you’d target because those are the ones that are probably affecting you in an economic sense,” said Colwell.
“Unfortunately, the work that we’ve done thus far, we can’t identify those calves at this time. We can’t predict any kind of impact.”