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Tall Fescue Toxicity Leads to the Development of "MaxQ"
Varieties provide the animal performance, stand survival producers want

ARDMORE, Okla. — Tall fescue is the cool season perennial grass grown on the most land area in the United States, including eastern Oklahoma and Texas. The majority of this acreage (by some estimates, more than 40 million acres) is naturally infected with a fungal endophyte called Neotyphodium coenophialum.Studies indicate that endophyte-infected (E+) tall fescue has enhanced growth, survival, drought tolerance and competitiveness. However, endophyte infection leads to "fescue toxicosis" in grazing animals. The condition is a result of ingestion of ergot alkaloids derived from the endophyte infection.

Fescue toxicosis is generally characterized by poor weight gain and reproduction in animals consuming the forage. Although the most common visual symptom is animals trying to cool their elevated body temperatures in ponds or defecation wallows, the negative effects of fescue toxicity on animal gains are striking and economically significant.

"The toxicity of endophyte-infected tall fescue, therefore, presents livestock producers with the dilemma of whether to grow E+ varieties for stand persistence, risking reduced animal performance because of the inherent toxins," said Dr. Joe Bouton, acting head of the Noble Foundation’s Forage Biotechnology Group and a professor at the University of Georgia.

"Since the vast majority of U.S. acreage — including newly planted pastures — is E+, most producers have decided that stand persistence, and not fescue toxicosis, is the most important consideration in their operation."

Surveys indicate that the main reasons farmers do not convert to endophyte-free (E-) pastures were lack of confidence in E- varieties and a perception that the benefits do not outweigh cost. The failure of E- varieties to assume a substantial share of the tall fescue seed market also supports this view.

"It goes without saying, therefore, that most livestock grazing tall fescue pastures in the United States probably suffer from some degree of fescue toxicosis," Bouton said. "Two general approaches currently are being pursued to overcome the fescue toxicosis problem — one is management of both pastures and animals to reduce toxicity in current E+ pastures and the other is development of persistent varieties that do not produce the problem ergot alkaloids."

For pasture management, the following options are currently used by producers: using E- tall fescue varieties with good summer management (rest); close grazing and periodic clipping of E+ forage to remove seedheads; use of pastures and/or hay of different forage species (bermudagrass) during vulnerable periods; and inter-planting E+ pastures with other forages.

"All are practiced to some degree, but the one with the greatest use and potential is inter-planting with legumes (clovers, alfalfa, etc.). The ability of even small amounts of legume to increase animal performance of E+ pastures is documented," he said. "However, even though animals are gaining better they are still experiencing symptoms of fescue toxicity."

For very sensitive animals such as horses, especially pregnant mares, complete removal from tall fescue pastures is the only recommended option. Direct treatment for relief of fescue toxicosis in less-sensitive animals such as beef cattle has concentrated on feed treatment and additives, pharmaceuticals, immunologic protection with anti-ergot sera and animal breeding and selection for better performance when grazing toxic tall fescue forage. Of these, pharmaceuticals, especially domperidone, have shown the most promise.

"Again, it should be emphasized that animals are still suffering from toxicosis and these treatments only alleviate some of the symptoms and not the main cause, which is the toxic fescue pasture itself," Bouton added.

Development of E- varieties persistent enough for the expectations of most livestock producers has not been successful to date, but is still being pursued by both private and public plant breeders, including Andy Hopkins at the Noble Foundation. The technique of isolating naturally-occurring, non-toxic endophyte strains and re-infecting these strains into elite varieties led to the commercialization of "MaxQ" tall fescue. MaxQ is actually a non-ergot, alkaloid-producing endophyte strain currently re-infected into the tall fescue varieties Jesup and Georgia 5.

"In proof-of-concept studies between the University of Georgia and AgResearch, New Zealand, MaxQ was found to provide better animal performance than E+ tall fescue and better stand survival than E- tall fescue," Bouton said.

With cows and calves at weaning, cow body condition scores were higher, and calves were 50 pounds heavier on MaxQ pastures compared to toxic E+ pastures. For stockers, average daily gains favored animals grazing MaxQ over E+ forages with these MaxQ gains comparable to contemporaries on E- pastures.

Hopkins and Foundation crops specialist Jim Johnson have recently found similar pasture stocker performance with MaxQ at the Foundation’s Red River farm. At no time — with all studies to date — have animals grazing MaxQ, including lambs and horses, showed classic fescue toxicosis symptoms.

"Tall fescue pastures in the United States will continue to be dominated by plants infected with toxic Neotyphodium endophytes, so research and extension efforts that allow producers to better deal with toxicity will need to continue," Bouton said. "The use of naturally-occurring strains like MaxQ is the latest effort to help with this and will need to be watched closely for its on-farm success."

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The Samuel Roberts Noble Foundation, headquartered in Ardmore, Okla., is a non-profit organization conducting agricultural, forage biotechnological, and plant biology research; providing grants to numerous non-profit charitable, educational and health organizations; and assisting farmers and ranchers through educational and consultative agricultural programs.

To learn more, visit the Noble Foundation Web site at http://www.noble.org.

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