AmericanFarm.com

VT forage researcher looking for fescue fungus solutions

By JANE W. GRAHAM
AFP Correspondent

RAPINE , Va. (March 24, 2015) — A grass that is both praised and cursed in the cattle industry will be the subject of some research at Virginia Tech’s Shenandoah Valley Agricultural Research and Extension Center beginning this spring.
Tall fescue and its strengths and weaknesses comes up in conservation many times cattle producers gather.
A research team led by Dr. Ben Tracy, a forage specialist at the university will be trying to find legumes that Tracy is quick to point out that managing tall fescue and the legumes that may help detoxify it is complicated.
“More work needs to be done though, and my research group is beginning work at the Shenandoah Valley AREC at Steeles Tavern to explore questions about tannin containing legumes in pasture situations,” Tracy wrote in a recent paper. “In the next few years, we hope to shed some light on these interesting legumes and the potential for dealing with fescue toxicity.”
Tracy has found that most people in the forage-livestock industry have a love-hate relationship with this grass.
“On one hand, it is one of the most persistent cool-season forage grasses in Virginia,” he stated. “On the other hand, animals regularly get sick if they consume too much of it.”
He estimates that about 90 percent of Virginia pastures have endophyte infected tall fescue.
He said that alternative forages can be used in place of tall fescue but this is an expensive process that is often unsuccessful. His team will be looking at some legumes that may help solve the problem.
This approach is based on recent research that points to possible solutions to the problem.
“This toxic fescue probably costs the livestock producers millions of lost revenue every year,” he wrote. “The toxicity actually comes from endemic fungus, Neotyphodiumnoenophialum, that grows inside the fescue plant. This mutualistic fungus produces chemicals (alkaloids) that negatively affect livestock in many ways, often producing a malady termed fescue toxicosis. Alkaloid chemicals make fescue aversive to animals so they eat less. Reproductive problems and increased heat stress are also common symptoms. Even though alkaloids are problematic for livestock, the same chemicals increase the survival of tall fescue plants by making them highly resistant to drought, grazing pressure, disease and insect pests.”
Tracy explained in a recent conversation that his team will be seeding sericia lespedeza and alfalfa into tall fescue stands at the SVAREC early this month and then mob grazing the plots.
They will be looking for what effects the legumes have, if any.
“It has long been known that some legumes contain chemicals called condensed tannins,” he said. “Probably the most familiar legumes here in Virginia are birdsfoot trefoil, sericiea lespedeza and crown vetch.
When consumed by animals, condensed tannins in legumes can bind to proteins like the alkaloids that make tall fescue toxic. In fact, recent evidence suggests that condensed tannins may help detoxify alkaloid toxins, make forage more palatable and help reduce heat stress in cattle. In addition to possible fescue detoxification, tannin-containing legumes also are well known to help prevent bloat and reduce parasite loads in animals. Condensed tannins may even help boost animal immune responses.”
From what Tracy knows so far, like many things that sound too good to be true there is the potential for this to be one of them. He said they present challenges.
“Legumes like birdsfoot trefoil and serciea are not easy to manage,” he reported. “Establishing these legumes in pasture is difficult, and managing them once established can be tricky. It is also good to remember that while condensed tannins can be beneficial in modest concentrations, if levels get too high, they can be toxic to animals as well.
Complicating matters even more is that fact that condensed tannins are quite variable in their chemical structure. The specific forms, or polymers, of condensed tannins that produce beneficial effects in animals is still not well understood. Nevertheless, if these legumes can help offset the negative effects of the alkaloids in tall fescue, livestock producers could have a ‘natural’ and cost effective avenue for coping with fescue toxicosis.”
Tracy and his team are hopeful their efforts over the next few years will help answer some of these questions.