As part of his research into how an ingredient in red clover, biochanin A, improves feed efficiency and weight gain in ruminants (see last week’s article), USDA Agricultural Research Service scientist Michael Flythe did his due diligence, looking for other possible effects of this isoflavone. This extra step led to his discovery that biochanin A can prevent fescue toxicosis.
“I wanted to know what happened to biochanin A and the other isoflavones after the rumen,” says Flythe, a research microbiologist for the USDA Agricultural Research Service. “It’s just good science to consider everything that your treatment might do to the animals.”
Flythe knew that biochanin A had to be absorbed because it had been reported as having estrogenic effects on sheep; their fertility was reduced. So he dug into the human nutritional and medical literature and found that isoflavones were explored as ways to relax constricted blood vessels to help with high blood pressure and other conditions.
“Then the lightbulb came on,” he says. “My colleagues, Dr. Glen Aiken and Dr. Jimmy Klotz, did research in fescue toxicosis. I knew from them that the ergot alkaloids made by the fungal endophyte in toxic tall fescue constricted blood vessels. Many of the problems associated with tall fescue, such as increased heat stress and gangrenous lameness (‘fescue foot’), are due to poor blood flow from vasoconstriction.”
Flythe knew that if isoflavones could work against the ergot alkaloids in tall fescue, it would explain the long standing observation that cattle perform better on tall fescue when there is clover in the pasture. So he tested his hypothesis in two experiments with goats.
In the first experiment six fistulated goats were given toxic tall fescue seed and red clover extract together for four days. Researchers used ultrasound to measure the size of the carotid artery and an artery in the front leg and found they were the same as in goats eating only orchard grass. Then they took the red clover extract away. The goats’ blood vessels constricted within 48 hours. In the second experiment, the goats received only fescue seed and the vessels became very constricted. When they began feeding red clover extract with the fescue seed, the vessels began to open up and in five days were normal.
So What’s Next? And How Much Red Clover Should You Plant?
Flythe has continued his research. He says, “Since then we have performed the measurements on steers grazing fescue with and without red clover. Those data aren’t published, but we are comfortable telling you that red clover mitigates vasoconstriction in fescue toxicosis.” But, he reminds us that, “Isoflavones are estrogenic, which means that they have to be carefully used. For example, different feeding levels might be recommended for backgrounding and finishing beef versus preweaning or in dairy production. There are also special considerations for sheep, which are believed to be particularly sensitive to reproductive effects of plant estrogens.”
(Check out this week’s article by Genevieve Slocum for ideas on establishing and managing red clover in your pastures.)
If Red Clover Doesn’t Work For You – Stay Tuned For Results of Additional Research
The team has also done experiments with white clover, soybean meal and soy hulls. All of them are promising. At this point they can’t say which is the best because those are new data, and need to go through peer review before being shared. Flythe says, “Clearly, more research is needed on the biologically active chemicals made by forage legumes, as well as how to best utilize them as “functional feed” in each industry supported by forage.”