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Drought dangers raise the red flag on toxicity for cattle

Experts are warning livestock producers to look out for toxicity as cattle scramble for feed in the pasture, drought raises nitrate risk and water supplies dwindle

Moisture-starved pastures have livestock foraging harder for feed, and provincial experts warn that toxic plants could be eaten accidentally.

Feed shortage may not be the only threat lurking in Manitoba’s increasingly brown pastures.

Manitoba Agriculture livestock specialist Jane Thornton says she would not be surprised by reports of poisoning from toxic plants or other toxicity issues as regular forage runs out.

“Producers should look at what they have in their fields for poisonous plants,” she said. “Western water hemlock is one that cattle will switch over to. Seaside arrowgrass is another one that kind of just looks like grass. They have to eat a lot of that one, but it can really reduce production or it can actually kill them.”

Manitoba Agriculture has declared four species of water hemlock as noxious weeds in Manitoba, including spotted water hemlock, which the Canadian Poisonous Plants Information System describes as, “the most violently toxic plant in North America,” causing spasms, convulsions, salivation, and rapid death in livestock.

Both western and spotted water hemlock have earned media headlines for their spread in Manitoba. Resources from the Manitoba Forage and Grassland Association cite most western water hemlock poisonings in the spring, when toxins persist through the entire plant, although the organization still counts the plant as a risk throughout the season, since a single root can cause swift death in even a mature cow late in the season.

The Canadian Poisonous Plants Information System lists a long string of toxic plants in Manitoba that have caused livestock problems. Stinkweed has been a problem during other dry spells. Hay fed with high concentrations of the weed have been linked to poisoning, abortions and death in western Canadian cattle herds in the past. Likewise, velvety golden rod has been noted to cause weight loss in cattle from its corrosive resin, ramping up to breathing issues, nausea, vomiting and even herd losses in sheep. Chokecherry leaves, meanwhile, contain prussic acid and might be a bane for cattle near woody areas.

“We don’t usually see livestock poisonings until you start running out of the forage they normally eat,” Thornton said.

“Running out,” describes pastures throughout Manitoba, save fortunate patches that saw rain this summer or regions in the northwest, which have reported normal to above-normal moisture.

Dropping dugout levels have producers concerned with salinity and water quality. photo: Alexis Stockford

Producers are already supplementing feed or removing cattle from pasture as of early to mid-August in dry areas, provincial extension staff report, while many rain-starved pastures are visibly short on feed.

Thornton also flagged nitrate risk and prussic acid poisoning.

Manitoba Agriculture cites drought as one of the stressors causing nitrate buildup, turning regularly palatable plants into a toxicity concern causing breathing problems, frothing at the mouth, weakness, speeding heart rate, diarrhea, convulsions, co-ordination problems and death within hours.

“If conditions improve and the plant starts actively growing, some of the accumulated nitrates may be used up in a few days,” the province says, although it notes that only top leaves may see that drop, and bottom leaves may still be high in nitrates.

Ensiling will drop nitrates 40 to 60 per cent, Manitoba Agriculture says, but there will be little drop in baled feed.

The province puts nitrate threshold in feed at 0.5 per cent.

Dr. Corey Jones of Melita’s Border Veterinary Animal Health Services said he hasn’t had any questions on nitrates yet, but expects more producers will be testing their feed as the year wears on.

“Some of the guys who are going to be putting up some of the drought-affected corn and some of the greenfeed… we’ll recommend that they do make those appropriate tests,” he said, adding that concern will be higher if farmers get an early frost before baling greenfeed.

Manitoba Beef Producers general manager Brian Lemon says producers are “cognizant,” of the risks, although he has not heard of any herd losses so far.

“Certainly, I think there are always a number of plants out there that have varying degrees of toxicity,” he said. “Hemlock is one. Even the leafy spurge, there’s a certain amount of toxicity there that if they’re at a point in the pastures where that’s all that’s left, certainly if they ingest enough of it, it can become a problem.”

Producers are typically aware of toxic symptoms and are on the watch for them, Lemon said.

Heat dangers

Jones encouraged producers to avoid moving animals during the heat of the day.

Temperatures reached a scorching 39.1 C in Morden, 38.2 C in Brandon and the high 30s through much of the rest of the province during the second week of August. The rising mercury prompted extended heat warnings that lasted through Aug. 12.

Animals, as much as us, suffer from heat stress and there is a possibility of even producing heat stroke in those cattle if you’re stressing them or moving them during the hottest parts of the day,” he said.

Deadly water

Water quality is also a concern.

Like with toxic plants, Lemon says MBP has not heard of any losses, although salinity problems have been reported.

The conditions are an unfortunate reminder of last year, when water quality was tied to cattle deaths in southwestern Saskatchewan.

Two hundred cattle were found dead last July near Shamrock, Sask., losses that were later attributed to the heat, dehydration, and sky-high sulphate levels. An investigation by the province’s chief veterinary officer later found 33,400 milligrams per litre of total dissolved solids in the water supply, while sulphate levels hovered at 24,000 milligrams per litre, well over three times the fatal level.

Some producers in Manitoba this year are hauling water to avoid similar problems, boost supply or to dodge issues such as the similarly toxic blue-green algae.

“You can see it coming, because, if there’s any water in the dugouts, it’s pretty disgusting,” Mike Duguid of Camp Morton said.

Set in the middle of one of the driest regions in the province, Duguid is pumping water into his dugouts to keep water levels up.

In the southwest, Jones said he had one producer turning to a secondary water source after dugouts ran dry.

“We’re encouraging people to keep an eye (on it). Especially with the extreme amount of heat that we’re seeing,” the veterinarian said.

About the author


Alexis Stockford

Alexis Stockford is a journalist and photographer with the Manitoba Co-operator. She previously reported with the Morden Times and was news editor of  campus newspaper, The Omega, at Thompson Rivers University in Kamloops, BC. She grew up on a mixed farm near Miami, Man.



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