CAMROSE, Alta. – The horrors of photosensitivity disease have occasionally stricken cattle across the Prairies, but producers may take some comfort in knowing it’s fairly rare.
And at least one cattle breed association is trying to eradicate the disease from its herds.
“In this area it doesn’t seem to be very common,” said Lyle Petrie, of the large animal clinic at the Western College of Veterinary Medicine in Saskatoon.
Photosensitivity diseases can cause cattle hides to burn, and in extreme cases, to dry, crack and break. The disease tends to affect light-colored animals.
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“I’ve seen a white Charolais bull die through photosensitization,” said Petrie. “His hide just lifted all at one time.”
A similar case recently occurred near Grenfell, in south-central Saskatchewan. A Charolais cow’s skin broke in ugly gashes from its nose to its tail. It was originally diagnosed as a cougar attack, but later modified to a diagnosis of photosensitivity disease.
After a story appeared in The Western Producer, a number of producers contacted the newspaper to detail similar experiences.
Brenda Pollard of Edam, Sask. reported a two-year-old Hereford cow had developed the disease, lost most of the skin on its neck, and was delayed in its milk production and fertility. The cow began hiding from sunlight the next summer.
Possible causes
She said her veterinarian told her the disease could have been caused by plants the animal had eaten, possibly fall rye at a certain stage and shepherd’s purse.
Petrie said photosensitivity disease can be caused by a number of agents. Plants such as St. John’s Wort and Ragwort contain photoactive compounds that can get into the bloodstream of an animal and react to sunlight in light-colored areas of the skin.
Producers should not be worried about the disease on their farms, Petrie said, because the plants that cause it are rare on the Canadian Prairies. They are more common in Washington state and Oregon, Petrie said.
But concerned producers can contact local agrologists to find out if weeds that can cause the problem exist in their areas.
It can also be caused by a fungus, Petrie said. The fungus, which is rare here but more common in New Zealand, causes liver damage in the animal. Chlorophyll gets into the bloodstream because it is not metabolized, and then reacts to sunlight on the animal’s skin.
As with the plants, the fungus is rare because of the dry, cold climate on the Canadian Prairies.
As well, some veterinary drugs can occasionally cause photosensitivity, but most are no longer used, Petrie said.
The condition can also be caused by a genetic disorder called protoporphyria. While rare, it is enough of a concern to the Canadian Limousin Association, which is trying to eradicate it from the breed.
Eliminate existence
“It’s been in existence and we’re aware of it and we want to eliminate it being a problem in the future,” said association executive manager Bev Leavitt.
For about the past year, the association has required people selling a fullblood bull or semen from a fullblood bull to test the animal for protoporphyria. By weeding out cattle that test positive for the disease, the Limousin association hopes to eliminate it from herds, Leavitt said.
Leavitt added that many cattle can have the disease for years without showing symptoms.
“They’re so sensitive to the sunlight they’ll go and hide in the shade,” she said. Also, some cattle can carry the disease genes without ever showing symptoms, so a test is the only sure way to tell.
