January 31, 2021

Article at Beef Business magazine

Awareness and analysis are winning the battle against mycotoxins

Jeff Gaye

If you are in one of the regions that has been experiencing some dry years, you might think you can relax a bit about ergot and other mycotoxins in your feed.

Not so, says Barry Shakley, Professor of Veterinary Toxicology at the University of Saskatchewan.

There are several variables that can affect the presence and the concentration of mould-related toxins in a feed supply, he says, and weather is just one of them. In fact, he is seeing a high number of tests coming back with elevated levels of ergot.

Of 700 tests in a year, Blakely said the lab has returned more than 100 with ergot levels over 1,000 parts per billion.

“It does vary from year to year. Alberta's bad this year and next year someone else is bad—Manitoba’s bad or Saskatchewan's bad. It's unpredictable based on the weather or what people are seeding,” he said.

Ergot is the most common problem, with vomitoxin a distant second with about half as many instances. Other mycotoxins were “a one-off here and there,” Blakely said.

“If you were going to focus on two mycotoxins, ergot mycotoxins and the vomitoxin or that group would be the ones to focus on.”

Grass crops are the species affected—peas, pulses, and alfalfa are not affected by the toxin-producing moulds. Rye and triticale are among the most susceptible crops, because the mould attacks the grass plant during the flowering stage. While most grasses flower for a day or so, rye and triticale can flower over a couple of weeks.

Brome grass growing in roadside ditches is another major source, and a serious problem because it contaminates the outer edges of crop fields.

Keeping ditch grasses cut is an important preventive measure. When moulds contaminate the crops on the edges of fields, it becomes that much harder to assess a feed supply’s level of contamination.

“Because the centre of the field is low and the outside is high, representative sampling is a real challenge on this,” Blakley said. “You can sample all you want and it's a guideline, it's a red flag, but you may have underestimated the number.”

Crop rotation, introducing non-susceptible crops for two or three years after a contamination is found, is effective for eliminating ergot. Another good technique is the nearly-forgotten practice of having a field lie fallow for a season.

“If you have ergot in the field, if you grind it in and harrow the field and so forth, it goes into the soil and the bugs in the soil break down the ergot sclerotia and they don't infest the next year,” Blakley said. “Summer fallowing became almost a thing of the past 10 or 20 years ago, we don't do it anymore. So the ergot says, ‘Oh lovely. I'm just going to grow every year, and every year it's going to get a little worse.’”

It’s not just crops that are affected. Blakely said the contamination is spreading into native grasslands, causing additional problems.

“Obviously, once they get into the native grasses, you've got a real problem because you can't just say, ‘well, we're going to rotate the crop this year.’ It's not going to work. And so it is either you plow up the native pasture or you don't,” he said.

“Some would say, ‘well we’ll spray it with fungicides.’ And that's hit-and-miss too, if you're not spraying at the right time of year. And whenever it rains, you're going to have a problem with that. So it's quite a big variable.”

The science around testing is still evolving. Blakley said the method of counting sclerotia in a litre of feed is not reliable because some are larger than others, and some produce more toxins than others.

Recent research also shows that a weight-based analysis doesn’t show a strong correlation to the amount of toxin in a sample.

“We encourage people to do the analytical thing, that's the actual concentration of the chemicals in there,” Blakely said.

The variation in the less-precise methods can make a big difference in the safety of the feed. In the counting method, a one-litre sample is normally considered contaminated if there are 10 sclerotia. Blakley said five per litre is a better, but still imprecise, standard.

Weight comparison is also flawed.

“Twenty or 30 years ago we didn't have all the fancy equipment to do this [analysis]. So you counterweighed it and the standard at CFIA was 0.1 to 0.3 per cent, and that's a little high,” Blakely said.

“Most of the feedlots are trying to stay under 0.04 per cent, so from that point of view it's an issue. And I can tell you that at 0.3, you're going to probably have an issue. So the data is a little outdated there, but it's the best they had at the time.”

Early in the new year, Prairie Diagnostic Services (PDS) expects to have an online mycotoxin calculator available on its website. Producers will be able to punch in numbers from their diagnostic reports and get information on mycotoxin concentrations and how that applies against the standard for different species of livestock.

“If you actually send in an analysis and you get a report back, it should say on the bottom of the report, if you require more interpretation you can either call me or you can try this mycotoxins calculator. All you do is punch in your concentrations and what percent of the ration, what you're feeding it to and it'll tell you the number,” Blakely said.

The advances in feed sample analysis, and the uptake among producers, have led to fewer clinical cases of illness due to mycotoxins. Outbreaks are usually in the winter, when more animals are on feed. And June crops from wet years tend to carry greater risk.

But the presence of mould does not necessarily correlate to the presence of toxins. This is especially true of mycotoxins other than ergot.

“The best example I can give on that is some years they swath their fields, and it rains. It snows and it melts,” Blakley said. “And by the time they get on the field, it's rotten as can be. Mould, mould, mould all over the place. We've analyzed lots of those and rarely do we find mycotoxins in that.

“And then we get another sample that looks pretty well free from mould and it's loaded with mycotoxins. So the correlation between looking at the feed for mould, and the mycotoxins, is really poor.”

There are three typical signs of mycotoxin-related illness in cattle. Of these, two—central nervous system agitation and spontaneous abortion—are far more common in the US than in Canada.

“But the one with the two forms we do see here is the gangrenous form,” Blakley said. Constriction of the vessels in the legs, ears and tails causes them to slough, “which is not good as an animal welfare issue,” he said.

Gangrene is irreversible.

“You don't have any trouble picking it up either. Their leg sloughs or the hoof sloughs usually.

“But early stages of that, when it's after a few days on this new feed, the animals’ hind end is affected. It looks like they're walking on their tiptoes, they're walking on eggshells kind of thing, tiptoeing around,” he said.

“It's a sign that they can have some pain sensation. Still, it hasn't been totally destroyed yet. If you take them off the ergot feed right now, they'll make an uneventful recovery. But once the necrosis sets in and the gangrene is there, it's irreversible.”

Blakley describes three ways of dealing with a contaminated feed supply. If it’s grain, you can colour-sort it or density-segregate to get rid of the ergot particles. This is reasonably successful, but pricey, he says.

Diluting the feed can also be successful.

And adding binders, based on clay or activated charcoal, can also work. A drawback to using the binding agents is that they can also bind to vitamins, depriving the cattle of essential nutrients.

Analyzing feed for mycotoxin contamination is a relatively recent development in livestock production, and it’s an ever-expanding part of PDS’s workload.

“Ten years ago we didn't even do it, and about 2015 everything blew up,” Blakley said.

Now it represents about 40 per cent of their toxicology workload, “and that includes all the minerals and the vitamins and a whole bunch of other nasty little chemicals and so forth. So it's a major issue.”

The lower frequency of illness is probably a result of more feed testing, he said. “Analyzing your feed for mycotoxins has now become a gold standard, whereas 10, 20 years ago, no one did it.

“The number of sick animals has declined dramatically. We were getting calls every day about how many herds of cattle were affected. Now we get the occasional call, not many. So that's made a difference from the producers’ point of view,” he said.

“It’s a hundred bucks well spent.”