Endophyte-free tall fescue: Should I be concerned about endophytes in forage grasses?

What are endophytes and what impact could they have on my livestock?

The term “endophyte” usually comes to a farmer’s attention in connection with tall fescue. This forage grass is extremely important in the southern United States and endophytes have a lot to do with it. An endophyte is a fungus that lives within the plant between cells. It is not a true parasite, but has a symbiotic relationship with the host plant. The endophyte receives water, nutrients and a structure in which to grow. It provides alkaloids to the plant which help protect it from drought, heat and plant-eating animals, including insects. The fungus develops along with the plant and concentrates in seeds. This assures the next generation of grass plants will also be “endophyte-infected.”

When consumed by cattle and other livestock, the toxic alkaloid contained in endophyte-infected tall fescue can cause foot and leg problems, reduced weight gain or weight loss, reduced milk production, digestive problems and reproductive problems, including abortion. The toxin is concentrated if the tall fescue is grazed or harvested under high soil nitrogen or drought conditions. If harvested tall fescue is fed out at a level of less than 50 percent of total dry matter in the ration, the toxin is not likely to cause a noticeable problem.

Different grass species are infected by specific endophytes. The tall fescue endophyte produces two main alkaloids, loline and ergovaline. The loline is not known to cause harmful effects in livestock. However, the ergovaline contains the same toxin as the ergot fungus which infects cereal grains and grasses. Ergot was the cause of occasional widespread human poisoning in medieval times when infected grains were harvested and consumed.

Although not common in Michigan, another endophyte-related health problem is called “ryegrass staggers.” Perennial ryegrass can contain endophytes that produce a toxin called lotitrem B, usually under droughty conditions or in a high soil nitrogen situation. If lotitrem B levels are high and animals consume enough of the infected perennial ryegrass, a nervous disorder can result.

Drought and pest resistance provided by endophytes in tall fescue and other forage grasses are important for yield and stand persistence in the southern United States. However, research has shown that persistence of these same grasses in more northern areas, including Michigan, is not influenced by the presence or absence of endophytes. Endophyte-free tall fescue seed varieties are recommended by Michigan State University Extension and should be used in Michigan for tall fescue seedings. Palatability has been an issue with tall fescue forage compared with other cool season species commonly grown in Michigan. Improved endophyte-free tall fescue varieties with softer leaves are now available, providing Michigan farmers with the opportunity to try high-yielding tall fescue in their forage programs. Results of tall fescue variety trials in Michigan are available online.

An informative publication, “Forage Fescues in the Northern USA,” from the University of Wisconsin provides more information on endophytes and their impact on forage and livestock production in fescue species.

For more Michigan forage information, visit the MSU Forage Connection website.

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