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March 17, 2023
By John LovettUniversity of Arkansas System Division of AgricultureArkansas Agricultural Experiment Station
Download a photo of sheep
FAYETTEVILLE, Ark. — Research conducted by the Arkansas Agricultural Experiment Station
using a red clover extract in feed shows promise in offsetting some of the adverse
effects of tall fescue toxicosis in livestock, a problem with an estimated $1 billion
impact in decreased production.
Many pastures in Arkansas and around the country are planted in Kentucky 31 tall fescue.
A toxic endophyte fungus that infects the grass causes constriction of blood vessels
in mammals. Decreased food intake is a side effect of what’s called “tall fescue toxicosis.”
Ken Coffey, animal science professor with the Arkansas Agricultural Experiment Station,
noted that reduction in feed intake is one of the symptoms of tall fescue toxicosis
and a major driver in reduced animal performance, which can mean fewer cow calves
born and lower weaning weights. Coffey said he has seen milk production in ewes drop
when exposed to the toxin to the point their lambs die from starvation.
Studies have shown that across the Tall Fescue Belt, where Kentucky-31 fescue predominantly
grows, tall fescue toxicosis has led to a 30 percent reduction in calf births and
a 70-pound reduction in weaning weights, Coffey said.
Effects of red clover
An Arkansas Agricultural Experiment Station study has shown a small amount of red
clover extract helped offset the effects of tall fescue toxicosis in sheep. But too
much red clover extract also decreased feed intake. Coffey expects the impact to be
similar in cattle.
"Clover has estrogenic compounds, and over the years, we've seen some positive things
with estrogenic compounds," Coffey said. "If you can get clover to grow in your pasture,
that's great, but many people can't keep the clovers, so we used an extract as a supplement
in the feed for the study."
How the research was conducted
Researchers offered Dorper lambs one of five diets of bermudagrass hay supplemented
with tall fescue seed for the study. In addition to a positive control of non-toxic
fescue seed, researchers offered lambs diets with toxic fescue seed with no red clover
extract or toxic fescue with 0.33, 0.67, or 1 percent of the diet as red clover extract.
In the 2022 experiment station study, lambs offered toxic fescue ate 36 percent less
than those offered the non-toxic diet. However, lambs on toxic fescue with 0.33 percent
red clover extract consumed 15 percent more overall and 6 percent more digestible
organic matter than those provided with toxic fescue without the red clover extract.
Coffey said digestible forage consumed directly relates to animal performance.
But there can be too much of a good thing. Greater concentrations of red clover extract
led to less food intake among lambs.
"The proper dose of red clover extract is still not a complete solution, like so many
other things that have been tried, but it does offer hope of offsetting a sizeable
portion of the toxicity," Coffey's said.
More research is needed
Coffey said that while the study's results are promising, more research is needed
to evaluate different red clover extract sources and better define estrogenic compound
concentrations. He would also like to see more evaluations of grazing and delivery
methods of the red clover extract to ruminants and study the impact of feeding red
clover leaves at low levels to sheep or cattle on toxic fescue.
"Research on this issue has been conducted over the past 70 years without the discovery
of a complete solution to the problem, indicating its complexity," Coffey wrote in
a study impact statement. "Dilution of tall fescue pastures with clovers has been
recommended for many years now, but clovers are difficult to maintain in many tall
fescue pastures because of the thin, drought-prone soils that much of the toxic fescue
The study was conducted on sheep instead of cattle at the experiment station to decrease
expense, improve accuracy and shorten the study timetable. As ruminants, sheep and
cattle have many physiological similarities that allow research material to translate
Coffey noted that fescue toxicosis mitigation tactics are something to do whenever
an animal is on tall fescue because the toxicity and impacts are variable throughout
"If they're on fescue and the forage is toxic, it costs performance. It's just a matter
of how much," Coffey said.
Coincidentally, Coffey's research has shown that tall fescue toxicity rises at a critical
season between mid-May and mid-June when ranchers reintroduce bulls to the herd for
breeding in a spring calving operation. Coffey said that seeds in affected plants
are five times more toxic than the leaves. He said that tall fescue's concentrations
of ergot alkaloids, the toxic compounds in endophyte fungus, also peak in the fall.
Coffey noted that some tall fescue varieties have a non-toxic endophyte and are safer
for ruminants to eat.Brittni Littlejohn, assistant professor of animal science for
the experiment station, has conducted studies testing melatonin to offset tall fescue toxicosis. Her research showed that pregnant cows consuming
toxic fescue seed have decreased uterine artery blood flow, potentially reducing nutrient
supply to bovine fetuses during gestation.
On average, calves in Littlejohn's study were about 90 pounds underweight at weaning.
The low weight level continued as the calves grew, and the differences were maintained
through the yearling stage. She was able to recover over 70 percent of the loss in
weaning weight by treating pregnant heifers with melatonin.
To learn more about Division of Agriculture research, visit the Arkansas Agricultural
Experiment Station website: https://aaes.uada.edu. Follow on Twitter at @ArkAgResearch. To learn more about the Division of Agriculture,
visit https://uada.edu/. Follow us on Twitter at @AgInArk. To learn about extension programs in Arkansas,
contact your local Cooperative Extension Service agent or visit www.uaex.uada.edu.
The University of Arkansas System Division of Agriculture’s mission is to strengthen
agriculture, communities, and families by connecting trusted research to the adoption
of best practices. Through the Agricultural Experiment Station and the Cooperative
Extension Service, the Division of Agriculture conducts research and extension work
within the nation’s historic land grant education system.
The Division of Agriculture is one of 20 entities within the University of Arkansas
System. It has offices in all 75 counties in Arkansas and faculty on five system campuses.
The University of Arkansas System Division of Agriculture offers all its Extension
and Research programs and services without regard to race, color, sex, gender identity,
sexual orientation, national origin, religion, age, disability, marital or veteran
status, genetic information, or any other legally protected status, and is an Affirmative
Action/Equal Opportunity Employer.
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Media Contact: John LovettU of A System Division of AgricultureArkansas Agricultural Experiment Station(479) firstname.lastname@example.org