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Pros and cons of fescue toxicity – Part VI

by Wyoming Livestock Roundup

Previously, I discussed some common syndromes of fescue toxicosis, including fescue toxicity problems in horses, reproduction problems in mares, including abortions, difficult birth (dystocia), longer or prolonged gestation, thickness in placenta, deaths of foals, retained placentas, little to no milk production (agalactia), mares’ death during foaling, some biology of the causal agent, benefits of fungal endophyte and endophyte-free tall fescue. 

Now, I will focus on non-toxic endophytes and their effects on tall fescue and animal performance. Tall fescue is a perennial cool-weather turf grass which stands out due to its growth habit. 

Non-toxic, or novel,
endophyte tall fescue

Non-toxic endophyte is often called novel endophyte. This is a unique technology offering a solution to the problems associated with tall fescue toxicity in livestock.  

The technology behind it is some strains of endophyte do not produce toxicalkaloids. Instead, they provide some benefits to tall fescue plants as toxic strains of endophyte. 

These non-toxic, or novel, endophyte strains can be inserted into varieties of endophyte-free tall fescue. There are several strains of non-toxic endophyte; however, their effectiveness varies with the varieties of tall fescue.

Research results from grazing studies on lambs, beef steers, beef cows and horses show animal performance grazed on novel endophyte tall fescue is excellent and very similar to tall fescue with no endophyte.  

In general, animal daily gain and total body weight are higher on novel endophyte tall fescue than on toxic endophyte tall fescue. As a result, animals grazed on novel endophyte tall fescue reach desirable slaughter weight faster than animals grazed on toxic endophyte tall fescue.

There are several other benefits from novel endophytes on tall fescue plants as well. For example, novel endophytes provide improved plant growth and vigor, better pest resistance and improved drought resistance and grazing tolerance compared to toxic endophyte tall fescue. This provides an additional advantage of overgrazing the tall fescue stands, especially in drought or stressed conditions. 

Although overgrazing is not recommended, as it could be detrimental for both novel and toxic endophyte tall fescue, using novel endophyte tall fescue has an obvious advantage in drought conditions and drought years.

Novel endophyte tall fescue became commercially available in the U.S. in 2000. There are several varieties of novel endophyte tall fescue currently available in the market. These varieties have no endophyte-related disorders and persisted well compared to toxic endophyte tall fescue. 

Therefore, it is recommended producers should consider using novel or non-toxic endophyte tall fescue where possible for better productivity and animal performance. 

Anowar Islam is a professor and the University of Wyoming Extension forage specialist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or

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