Extension specialists in Missouri say winter weather is aggravating the effects of cattle grazing endophyte infected tall fescue.
University of Missouri extension forage specialist Craig Roberts says cows grazing toxic fescue can suffer frozen feet and lost hooves. He reports one case in Missouri where a producer lost 5 cows from a herd of 30.
The alkaloid in the old endophyte fungus causes blood vessels to contract. During the winter this vasoconstrictor shuts blood flow to body extremities, meaning feet, tails and ears can freeze.
Roberts says a cow can survive a lost tail switch, but once the foot is frozen and the hoof falls off, the cow cannot be cured and she must be put down.
Toxic fescue can cause other cow herd problems such as abortions and lower daily gains. The total economic loss from toxic fescue is estimated at $900 million a year.
Roberts says the only remedy is to replace toxic fescue with a novel-endophyte variety and he encourages producers to contact their local Extension agent for more information about reseeding their pastures.