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New Clues on Cow Fertility
Fertility Study Looks at Ovulation's Intricate
Workings
ARS News Service
Agricultural Research Service, USDA
Erin Peabody, (301) 504-1624
May 31, 2005
Agricultural Research Service (ARS) scientists are getting ever closer to
finding out what makes animals tick reproductively. In efforts to boost
fertility in beef cattle, researchers have discovered that the follicle--a tiny
structure within a cow's ovary that releases the egg--must reach full maturity
for pregnancy to have the best chance of success.
Pinpointing which hormonal cues enable the follicle to attain maturity is still
keeping the scientists busy--but their findings are already important for
livestock producers who would like to artificially inseminate all of their beef
cows at the same time. The study could also shed light on issues concerning
human fertility. ~
Tom Geary, a reproductive physiologist at ARS' Fort Keogh Livestock and Range
Research Laboratory in Miles City, Mont., helped conduct the studies, along with
reproductive physiologist Michael Smith at the University of Missouri-Columbia.
George Perry, a graduate student who worked with Geary and Smith before joining
the Animal and Range Science Department at South Dakota State University in
Brookings, once theorized that follicle size might be the best indicator of a
cow's readiness to ovulate and establish a pregnancy.
But in a recent study, the researchers found that when cows were allowed to
naturally ovulate, it didn't matter what size their follicles were--their bodies
intuitively knew when the tiny, blister like structures were ready to release
the eggs.
To induce ovulation in cows, beef producers administer the hormone known as GnRH.
As the study points out, if the hormone is injected before a follicle is mature
enough, pregnancy has a lower chance of success.
Follicular cells may not be fully developed at the time of induced ovulation
because they're not producing enough estrogen, according to Geary. So he and
other Ft. Keogh researchers are currently looking to see if extra estrogen helps
coax follicle maturity along. This work could lead to higher fertility rates in
industry artificial insemination programs.
The researchers' studies relating to follicle maturity were published recently
in the Proceedings of the National Academy of Sciences.
ARS is the chief scientific research agency of the U.S. Department of
Agriculture.
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