In severe cold weather, cows eating toxic fescue can suffer frozen feet with lost hooves. In one case, a Missouri producer lost five cows out of a herd of 30. Other less-severe cases are also being reported, said Craig Roberts, a forage specialist at the University of Missouri.
While it’s too late to solve the problem this year, improving pastures can help prevent the problem in the future, he said.
“We’ve known prevention for 15 years,” Roberts said. “There are ways to reduce the problem but only one preventive: replace toxic fescue with a new variety.”
Fescue foot is caused by ingestion of an alkaloid from a fungus growing inside toxic endophyte varieties of tall fescue. The alkaloid is a vasoconstrictor, causing blood vessels to contract and shutting off flow to body extremities. In the winter, feet, tails and ears can freeze.
Cows can survive a lost tail switch, but animals crippled from the loss of a hoof cannot walk to graze. They must be put down.
Low blood flow in summer causes heat stress. While not fatal, it can cause unseen economic losses. Cows in heat stress quit grazing and head to shade or to ponds to cool off, Roberts explained. Animals that stop grazing stop gaining weight. That loss cuts farm income when calves are sold.
Fescue foot was first reported 75 years ago, but it took until 1977 to discover the cause was an endophyte fungus, a threadlike growth that lives between plant cells in the grass. It’s a symbiotic relationship. The endophyte protects fescue from insects, diseases, drought and overgrazing.
Other naturally occurring endophytes give protection but don’t have the vasoconstrictor alkaloid, Roberts said. Through breeding programs, these “novel-endophyte” fescue varieties have become more prevalent in the seed market.
“Replacing toxic fescue with a novel-endophyte variety has huge economic benefit,” he said. “However, it does require a season-long process to kill the old variety and reseed to new fescue.”
Roberts warns that seeding an endophyte-free fescue doesn’t work.
“We tried that in Missouri,” he said. “Fescue needs endophyte protection to survive much past one year.”
While fescue foot can be critical and costly, other losses attributed to the old endophyte fescue are mostly unseen, he added. In fact, fescue foot is third or fourth down the list of losses. Early abortion of unborn calves and lowered daily weight gains pose bigger threats to herd profitability.
“That can mean a big loss on payday,” Roberts said.
Fescue foot cases drop as the weather warms up, but other losses continue in all seasons.
“We know how to prevent losses, estimated at $900 million a year,” Roberts said. “Producers solve problems and increase profits by planting novel-endophyte fescue.”