Phytoestrogens: Something to be Aware of, But Don’t Overreact!
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On occasion we receive inquires about the effect of phytoestrogens on reproductive performance of cattle. There have been a few reports from nutrition consultants and veterinarians working with well managed herds which experienced a sudden decline in reproductive performance for no obvious reason but when forages suspected to have high concentrations of phytoestrogens were removed from the ration performance improved. It is difficult to find well controlled studies which document how widespread this condition might be. However there are some good review articles describing the effect of phytoestrogens on sheep and cattle.
On occasion we receive inquires about the effect of phytoestrogens on reproductive performance of cattle. There have been a few reports from nutrition consultants and veterinarians working with well managed herds which experienced a sudden decline in reproductive performance for no obvious reason but when forages suspected to have high concentrations of phytoestrogens were removed from the ration performance improved. It is difficult to find well controlled studies which document how widespread this condition might be. However there are some good review articles describing the effect of phytoestrogens on sheep and cattle.
Three such articles are as follows:
- Forage Plant Estrogens. A. L. Livingston, Journal of Toxicology and Environmental Health. 4: 301. 1978.
- Toxicological Problems in Food Animals
Affecting Reproduction. M. R. Putnam,
Clinical Toxicology, In: Veterinary Clinics of
North America: Food Animal Practice.
5: 325. 1989.
- Detection of the Effects of Phytoestrogens on
Sheep and Cattle. N. R. Adams, J. Animal
Science. 73: 1509. 1995.
Here are some major points abstracted from these articles:
- Phytoestrogens are a diverse group of naturally
occurring non steroidal plant compounds that,
because of their structural similarity with
estradiol have the ability to cause estrogenic
or/and antiestrogenic effects.
- The major plants producing phytoestrogens
that are of importance to animal agriculture are
legumes, clovers (subterranean and red) and
alfalfa. Selection and breeding of clovers has
provided varieties low in phytoestrogens. Sheep
are most sensitive to these substances. Alfalfa
generally contains very minimal amounts of
phytoestrogens. Aphids and fungi may induce
production of these compounds. Several other
factors affect the production of phytoestrogens.
One study showed that field-curing hay reduced
estrogenic activity somewhat while ensiling
preserved the concentrations of these
compounds.
- The phytoestrogens of most concern are
isoflavones and coumestans. Red clover silage
with isoflavones and alfalfa containing
coumestans has been reported to affect fertility
in cattle. The research team of Alder and
Trainin (1960) reported that feeding alfalfa
with high levels of coumestans (> 25 μg
equivalents of estradiol / lb. of feed) adversely
affected performance. The symptoms of
estrogenism included precocious mammary
development and genital development in
heifers, irregular estrus cycles, cystic ovaries,
low conception rate in cows and even anestrus.
They further reported reproductive perform-
ance improved several months after removal of
this specific feed source.
- N. R. Adams (1989) reported the estrogenicity
of coumestans and isoflavones are approxi-
mately 1/1,000 and 1/ 10,000 compared to the
activity of estradiol, respectively. However,
there are no reports that phytoestrogens induce
estrous behavior.
- Laboratory analysis of the forages should be
performed to document the levels of these
compounds. My colleague, Dr.Van Saun,
directed me to the Diagnostic Laboratory at
North Dakota State for testing for phytoestro-
gens. This laboratory also has an excellent
mycotoxin screening test. Here is a link to the
list of tests, scroll down to toxicology:
www.vdl.ndsu.edu/vdl/FeeSchedule.aspx?
f=services&sf=giv. Your nutritionist and
veterinarian may know of other reputable
testing laboratories.
There is a need for a comprehensive well-controlled study to document the prevalence of the problem. Frequently toxins and phytoestrogens are blamed for poor reproductive performance when management problems and herd health issues are the likely factors involved.
Before focusing attention on phytoestrogens or other toxins as the potential cause for lowered reproductive performance, it is important that a thorough review of herd reproductive management practices and herd health be performed.
Based upon that analysis, a list of bottlenecks likely restricting performance and an action plan to address those issues should be developed. If the management team and associated consultants feel that phytoestrogens or other toxins may be involved then appropriate testing should be performed.
.....................
Michael O’Connor,
Dairy and Animal Science Extension
