Tuesday, September 21, 2021
Sept. 21, 2021

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Herbicides Hurting Hooves?

Some wonder if there is a chemical explanation for hoof rot disease

The Columbian
Published:

When Krystal Davies moved herself and her horses to the Kalama area in March, she started noticing something on their hooves. Her 5-year-old horse, Tucker, had previously had only one abscess.

“Since I moved up here, he’s had 10,” she said. “Typically, you’re not going to get abscesses in healthy feet.”

Davies is a farrier — or horseshoeing expert — and is among the growing number of people asking if the use of herbicides on private timber lands is related to animals’ health. She lives adjacent to Weyerhaeuser Co. land she says was recently logged, and she used to ride her horses on the company’s property until she noticed the abscesses.

Davies, who calls herself “kind of a hoof geek,” started to do her own research about herbicides after noticing similarities between her horses’ hoof problems and those with elk that have hoof rot.

Davies is one of several people who have implicated herbicides during recent meetings about elk hoof disease. When Bruce Barnes of Vancouver asked for a show of hands during a hoof rot meeting in Longview in March, most of the people in the room indicated that they thought herbicides were a factor. Barnes has called for a moratorium on herbicide spraying on forest lands, an idea that has not gone anywhere with state agencies.

Herbicide experts who are advising the state Department of Fish and Wildlife have said there is no evidence that herbicides used on forest land have any direct harmful effects on elk or other animals.

“Anything people can’t explain, they try to put it onto pesticides,” said Anne Fairbrother, a veterinarian who gave a presentation about herbicides to WDFW’s hoof disease scientist advisory board.

But some hoof rot activists, including Mark Smith of Toutle, think that even if herbicides do not harm elk directly, they change the amount and type of forage for elk. That leads to nutritional shortages that make the animals more susceptible to disease, Smith said.

“We’ve logged the forest, but they don’t mitigate the damage,” Smith said.

Timber companies spray herbicides on clearcuts to kill plants that compete with newly planted conifers for water, sun and nutrients, typically one or two more times in the first few years after replanting. The companies used to burn newly logged areas but concerns about air quality prompted them to switch to herbicides in the late 1990s.

Vickie Tatum, a Florida-based toxicologist for the National Council for Air and Stream Improvement, said herbicides’ effect has been widely researched.

“There is nothing in that body of research that suggests that any herbicide used in forests could or would have any relationship whatsoever to hoof rot,” said Tatum, who also participated in the Weyerhaeuser tour.

The overall effect of herbicide treatments on elk forage is “likely of short duration and probably has less impact on nutritional resources for elk than effects from widespread declines in timber harvest” in the Northwest, according to a paper published recently by Andrew Geary, a researcher at the University of Alberta who has studied elk nutrition at Mount St. Helens.

The overall effect of herbicide treatments on elk forage is “likely of short duration and probably has less impact on nutritional resources for elk than effects from widespread declines in timber harvest” in the Northwest, Geary wrote.

Those questioning herbicide use point out that WDFW’s invited experts have been funded by the forest products industry.

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