MFA Technical brief
by Dr. Jim White
Get along with fescue
By a good margin, tall fescue is the most common cool-season pasture grass in Missouri. Most of it is endophyte infected—hosting the fungus Neotyphodium coenophialum. The concern with the fungus growing inside the plant is that, although the fungus improves the survivability of the fescue, it also produces ergot alkaloids, which are toxic to animals. From a plant’s perspective, this is great— the fungus improves the plant’s ability to compete and hammers plant predators. That hammering includes your beef herd. Cattle consuming ergot alkaloids suffer from heat stress, weight loss, decreased fertility and other ills. To counter the herd health issues with endophyte-infected fescue, producers have planted endophyte-free varieties. These varieties do improve animal performance, but, so far, stand persistence has been low— especially if the area is prone to drought. Novel endophytes have been more promising.
Ergot alkaloids produced by the endophyte include: lysergic acid, clavine alkaloids and ergopeptines. The alkaloids are found in stem, leaf and seed tissue, but they are highly concentrated in the seed. Most research has been done on the compound ergovaline, but there is ongoing discussion as to which compounds actually cause the problems. In the spring, the plant’s concentration of alkaloid levels jump as soon as heads appear; they decline during fescue’s dormant summer stage, then spike up again in the fall when growth picks back up.
The biggest reduction in animal performance seems to occur when the levels of toxic compounds in the plants are falling or flat. This indicates that there is a lingering effect of consuming infected fescue. In the spring, animals eat high levels. As summer moves on, heat stress makes the situation worse. The thought in the field is that it takes 6 to 8 weeks to clear an animal of toxins once you have stopped feeding infected fescue.
A common recommendation for pregnant mares is to pull the mares off of fescue their last trimester. Heat abatement helps (shade, fans, misters) in compensating for heat stress.
“Fescue foot” or tails falling off are pretty dramatic signs of problems with infected fescue. Most of the time, far milder things are seen. Symptoms can include calves not shedding their winter coats, increased body temperature, increased breathing rate, standing in ponds, low feed intake, low daily gain, etc.
You will also see reproductive problems such as little or no milk, calving problems, thick placentas, cows that didn’t clean, etc. The ergot alkaloids can be stored in body in the fat, which explains some of the things we see with fat necrosis and weird fat metabolism. Likewise, body fat can be a reservoir of the alkaloids, becoming a bigger problem when the animal loses weight.
At this time, we think that dealing with fescue and animals comes down to dealing with the amount of ergot alkaloids. For rough work, estimate that for every 10 percent infection you have on a fescue pasture, you lose 0.1 pound of average daily gain. Yes, animals can lose weight on fescue pastures.
Some things that really are good for grass such as high amounts of nitrogen make it more challenging to handle the alkaloids because alkaloid concentration increases with increasing nitrogen applications.
From an animal perspective, you need to do something about the load the animals are eating prior to seeing the symptoms, for example, pulling mares off of fescue the last trimester.
Getting rid of the fescue
If you have over 50 percent infection in a pasture, there are agronomic options to improve the forage base. But it must be said: Killing an established stand of fescue can be tough. The reason we have so many infected fescue fields is that fescue, especially endophyte-infected fescue, is a survivor. You should check with an agronomist, but I would suggest that to establish a different species, start 6 to 8 months before you want to establish the new pasture. For example, if you plan to introduce orchardgrass, in the spring graze that pasture hard or mow the offending fescue pasture—then pop it with Roundup. After that, thickly seed a summer annual—say a Sudan or millet—and graze or hay the summer annual. Then put on more glyphosate prior to putting in the new coolseason grass. This approach is called the spray-smother-spray approach for pasture renovation. Again, ask your local agronomists for details on such a program.
Deal with the fescue you have
Limiting nitrogen applications will tend to reduce ergot alkaloids, but it will also reduce the amount of forage available to your herd, and I am not a fan for managing for low yields. If you do reduce nitrogen to growing pasture, you can plan on ammonization of hay. Ammonization works best with straws; it is not well used in vegetative cool-season grasses. The ammonization of fescue straw does seem to destroy some of the alkaloids, and with removal of the seed, a major source of alkaloids is gone. Ammonization of straw increases the crude protein equivalent and increases fiber digestibility. But, even greatly improving extremely low quality forage may still leave you with low quality forage.
Dilution
Aggressive legumes, such as a red clover, will dilute the fescue. Often a couple pounds of clover seed are put in whenever fertilizer is spread. Animal performance on highly infected fescue with clover is expected to be lower than animal performance on non-infected fescue.
Use concentrates
In supplemental feeding of concentrates, the gold standard is hand feeding at 0.25 percent to 0.5 percent of body weight a day. Feeding concentrates to growing calves substantially improves their performance. If you need to offer feed ad lib, MFA Cadence or Cadence/commodity mixes are the products of choice for cattle. Again, the idea is to dilute the intake of toxins from infected fescue. When dealing with horses, dilution does not work with pregnant mares. Pull them off infected pasture.
Plan pastures
You can work around endophyte-infected fescue pastures with a grazing plan and timing. Use non-fescue summer pastures, usually warm-season grasses and stockpile fescue for later grazing. Work at MU has shown alkaloid concentrations fall during the winter.
Management in a feed bag
Over the years I have seen a number of feed additives studied: glucans, seaweed, yeast cell walls, clays, thiamine, niacin, essential oils, diatomaceous earth, CTC, Bovatec, etc.
If I had to use infected fescue, my first preference would be to feed about 0.50 percent to 2 percent bodyweight of a complete feed. In the spring and fall, during rapid growth, I would pick up the effects of dilution, better protein efficiency, additive effects and trace mineral-vitamin supplementation. During winter feeding of stockpiled fescue, the alkaloids are lower, so for cows I’d feed 2 to 4 pounds of supplemental feed—something like Super Cubes. If hand feeding, I’d use Trendsetter on the calves. If I were in a situation where I was only using a mineral addition, I would use a mineral balanced for cool-season grasses. The product of choice would be Fescue Equalizer MAX, which has aggressive levels of vitamin A, zinc and copper.
Dr. Jim White is a nutritionist for MFA Incorporated.
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