I recently had a phone call from a veterinarian describing unusual symptoms in a group of cows coming home off pasture.
The cattle were well vaccinated and were displaying signs of being off feed and had lesions around their muzzle areas.
Although we didn’t have a definitive diagnosis, it reminded me of a case I dealt with years ago that was somewhat similar.
It had been a very dry growing season with some late rains in the fall, which are conditions we’ve seen in some places in the Prairies this year.
It was now early February, and the farm manager had just begun to feed some barley green feed bales to a group of 90 cows.
Within a few days, we had multiple cows affected with severe ulcerations of the muzzle and oral cavity, diarrhea, and several abortions had occurred.
A number of the affected cows were down, some had diarrhea and some had severe lameness caused by vascular damage to their feet resulting in sloughing of hoofs. A few cows had some evidence of blood vessel damage in their ears as well and the edge of their ears sloughed off in the cold weather.
Eventually, 12 cows either died or had to be euthanized. At necropsy, the major finding was severe edema and swelling of the rumen lining.
We surmised that these cows were suffering from a plant toxicity. The cattle had consumed significant amounts of field pennycress, which had been present in the baled barley green feed they had been fed. The Latin name for field pennycress is Thlaspi arvense, however it goes by many other names such as pennygrass, fanweed, frenchweed, and perhaps most commonly known as stinkweed.
Stinkweed or field pennycress is a member of the mustard family. The plant is native to Europe but has been a widespread invasive plant in North America for several hundred years. It is an annual or winter annual with smooth erect stems and the lower leaves may form a rosette. Leaves are alternate, without hairs and the flowers are small, and have white petals.
Stinkweed has a very tough seed coat and as a result, the seeds can remain viable in the soil for as long as six to seven years. The plant germinates early in the spring, but also has a second emergence in the fall.
As a result, stinkweed can flourish in drought conditions and researchers from Alberta in 1984 described very similar cases in cattle when a severe drought affected southern Alberta.
In that situation, the producers fed hay that was composed of a high percentage of stinkweed.
The herds affected had similar symptoms of severe colic, going down and damage to the rumen wall. Abortions and kidney failure occurred in a number of the cases as well.
The toxic element in stinkweed is mostly concentrated in the seeds. The chemical allylisthiocyante is an oil glucocide and is highly concentrated in the seed. This mustard oil is highly irritating and causes severe damage to the gastrointestinal tract and the oral lesions may be caused when the cattle either consume the seed or when they chew their cud.
The severe irritation causes colic-like symptoms and probably damages the rumen wall integrity, which may lead to other complications.
The particular case that I dealt with almost 15 years ago was probably exacerbated by the late fall rains that delayed the harvesting of the barley green feed, which allowed the seeds to develop in the stinkweed plants to a greater extent.
A dry growing season also allowed the stinkweed to flourish in the field.
I’m not convinced that the case that was described to me by a veterinarian this year was definitely caused by stinkweed, but it certainly sounded similar.
It also reminded me that in a year where we’ve had a significant drought and cow-calf producers are forced to use feed they might not normally use, we tend to see more unusual toxicities.
John Campbell is a professor in the department of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.
