Fescue toxicity: Fighting the battle

Mar 28, 2019

We know that consuming KY-31 tall fescue forages presents some potentially negative side effects for cattle, but do you know the origins of the popular grass? Sam Strahan and Dr. Anne Koontz discuss the history of the grass as well as some management strategies to reduce the toxic effects of the endophyte.


Tom:                            I’m Tom Martin and I’m joined here in the studio by Dr. Anne Koontz, a research scientist in ruminant nutrition for Alltech®. And, on the line, from Madison, Virginia, Sam Strahan, a nutritionist with CRYSTALYX® Brand Supplements. Anne and Sam are with us to talk about the fight against fescue toxicity. And, we thank you both joining us.

Anne:                           It’s a pleasure to be here.

Sam:                            Glad to be here.

Tom:                            And, can each of you — one at a time — give us some background on Kentucky 31 tall fescue as a major grass species for cattle?

Sam:                            Be glad to do that.

                                    Tall fescue was first discovered in the US in 1931 by Dr. E.N. Fergus and he was an Agronomy professor at the University of Kentucky, so the name was given based on the location and the year discovered. 

CLICK HERE to download e-guide on how to address fescue toxicity

Dr. Fergus noted it’s many attractive agronomic characteristics, including hardiness under many climatic conditions. It’s also very persistent under heavy animal pressure, and is tolerant to close-grazing, which can also help to prevent erosion on steep hillsides.  It’s also resistant to insect pressure.

                                    Because of these positive attributes, the seed was widely planted and now represents over 35 million acres of grazing land in the Midwest, Mid-Atlantic, and Southeast US.

Anne:                           That’s exactly right. And to me, the history of tall fescue is particularly interesting. Tall fescue as a species itself came over from Europe on various ships as they were importing various crops for agriculture, and somewhere along the way, picked up this endophyte that gave it these characteristics of hardiness, disease-resistance and pest-resistance. And then, when those characteristics in particular were discovered in this particular varietal, Kentucky 31 as we know it came to be.

Tom:                            So, what are the issues surrounding Kentucky 31 fescue for the cattle who consume this forage?

Sam:                            Well, contributing to the hardiness of the plant, Kentucky 31 fescue usually contains an endophyte — as alluded to by Dr. Koontz — which is a type of fungus that lives symbiotically inside the plant. This endophyte produces chemical toxins called ergot alkaloids, which makes the grass less palatable than many cool-season grasses for both insects and grazing livestock.

                                    These endophyte toxins cause problems in cattle such as higher body temperatures due to restrictions of blood flow to the extremities, which limits heat escaping from the body, increases respiration rates or panting and reduces intake, reproduction rates, weight gain and milk production.

                                    The lowered milk production is due at least in part to a decreased level of the hormone prolactin, which is involved in stimulating milk production. So, obviously these are major impacts on the main parameters that we measure in cattle production.

                                    One study from a few years ago [showed that] losses from reduced growth of reproduction from fescue toxicity were estimated to be over $3.2 billion. Recommendations from a recent University of Kentucky Extension Bulletin gave the following recommendations: “Avoid grazing endophyte-infected pastures during critical times. Don’t graze high-endophyte pastures just before calving and just before breeding. If possible, graze other species for around 60 days after calving.”

Related: Fighting the fescue toxicity battle

                                    As you’re probably aware, [the times] just before calving and just before breeding are very critical periods in a cow-calf life cycle, so this is a good recommendation, but not always so easy to accomplish on a beef farm, especially in a spring-calving herd when the highest-quality pasture of the year is available at this time.

Tom:                            So, are there some management strategies that can be employed to reduce the toxic effects of the endophyte?

Sam:                            For many years, standard management recommendations to reduce negative effects included diluting fescue pastures with forages such as clover, or renovating fescue pastures with other cool-season forages, including what’s referred to as novel endophyte fescue, meaning these grass varieties contain an endophyte, but they did not elicit toxic compounds. Also, if we provide other feeds in the diet, this will further dilute the toxic compounds consumed.

                                    More recently, some commercial products, including Alltech’s FEB-200® have been researched and found to have an impact on the [nutritional deficiencies that result from the] toxins. And, Dr. Koontz can allude more to the effect of FEB-200.

Anne:                           Right, so, FEB-200 is a particularly interesting technology that Alltech has developed, and it’s designed to support animal health and production, particularly when those cattle are grazing fescue.

                                    So, as we’ve mentioned in some previous questions, the changes in blood flow within cattle are caused by this endophyte consumption, and that ultimately increases the animal’s body temperature. And, it’s part of the reason that these animals spend more time in shade or standing in ponds trying to cool off and ultimately not spending as much time grazing and growing and getting those nutrients they need for health.

                                    So, we’ve done several trials with this particular product and it showed that we can ultimately, again, support the health of those animals by reducing the body temperature, which allows those animals to spend more time grazing and increase their intake. We’ve also done some performance trials beyond that over a two-year period with some stocker calves on grazing fescue, and those animals have better average daily gains and the cows in that herd have better body condition scores.

Tom:                            I believe each of you has touched on symptoms of fescue toxicity in cattle, but could we drill down into that for a moment? What are some of the signs of fescue toxicity?

Sam:                            Sure — there [are] several classic signs we see such as rough hair coat in the spring with cattle slow to shed their winter hair. The hair coat often has a reddish tint, which is indicative of or similar to copper deficiency. Additionally, cattle will often stand in ponds (as already mentioned) to relieve heat stress and lie in the shade during hotter parts of the day instead of grazing.

                                    Because cattle are not spending more time grazing this is why we tend to see lower weight gains for instance in backgrounding or stocker cattle, plus it can contribute to lower milk production. While these are mostly signs that we see during the warmer part of the year, there [are] also some classic signs that we occasionally see during cold weather. One of these is called fescue foot, which is the loss of a hoof or one of the feet due to lack of blood flow to the extremities, which is caused by the toxins. Loss of tail switches can also be a similar sign of toxicity.

Tom:                            Anne, can you elaborate on what’s going on here physiologically in cattle that causes these symptoms that we see?

Anne:                           Sure, absolutely. So, there [are] two main things that I want to touch on. The fescue toxicosis affects a wide range of systems within the animal’s body, but the two that sort of have the most broad-reaching effects are changes in vascular tissues.

                                    So, the ergot alkaloids that are consumed actually bind to receptors on blood vessels and cause them to constrict. So, that constriction reduces blood flow to the skin and other extremities which is what ultimately causes that loss of tail switch or fescue foot that we can see in these animals.

                                    Now, the second big effect that’s particularly interesting is a change in passage rate through the gut. So, you actually see that food that’s consumed by these cattle takes longer to move through the digestive tract. And because there’s only so much space in the digestive tract itself; because it’s taking longer to move through, these animals get full faster and that contributes to not wanting to consume grass and continue grazing, ultimately leading to that reduction in growth rate on these animals.

Tom:                            Sam, can you tell us how CRYSTALYX® products help reduce some of the production issues observed with fescue [challenges]?

Sam:                            Absolutely. We’ve included FEB-200 in a number of our CRYSTALYX products and some of these include Fescue-lyx®, Hi-Mag Fescue-lyx®, Fescue-Phos®, and, most recently, we’ve added it to our Blueprint® Fescue Mag with FEB-200™.

                                    While we know the positive effects of FEB-200, research has also shown that copper availability is lowered in toxic fescue, so each of these products has elevated levels of copper and zinc. Fescue-Phos® and Blueprint® Fescue-Mag with FEB-200™ also include Bioplex® Hi-Four, the organic forms of copper, zinc, manganese and cobalt.

                                    So, by providing a very palatable nutritional package with FEB-200 through a CRYSTALYX block, we’re confident the proper level of intake will be on target and cattle will receive a complete nutritional supplement to help offset some of the deleterious effects of [fescue] that we see.

Tom:                            Dr. Anne Koontz, a research scientist in ruminant nutrition for Alltech and Sam Strahan, a nutritionist with CRYSTALYX Brand Supplements. Thanks, Anne and Sam.

Anne:                           Thank you, Tom.

Sam:                            Thank you, Tom. Appreciate it.


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