(Friday, Nov. 15, 2002 -- CropChoice news) --Iowa State University
researchers have addressed concerns about genetically modified corn
causing higher-than-normal pseudopregnancy rates in sows. After
conducting research they have determined that Bacillus thuringlensis corn
is not to blame.
A gene from soil bacterium is added to corn to produce Bt corn. This gene
helps to combat the yield-reducing European corn borer.
After conducting the research, John Carr, assistant professor of
diagnostic and production animal medicine; Thomas Carson, professor of
veterinary medicine; and Gary Munkvold, associate professor of plant
pathology, concluded that the Bt corn did not cause the pseudopregnancy
problems.
Included in the research were five farms experiencing reproductive
problems and two farms where no fertility problems existed. All seven of
the farms used Bt corn and non-Bt corn as livestock feed. Several
varieties of Bt corn hybrids were used in the feed. The farms were
located throughout the state.
"I'm happy to say that Bt corn itself doesn't cause pseudopregnancy
problems," Carr said. "Pseudopregnancy has been recognized for many
years and is present on pig farms throughout the world, irrespective of
the type or consistency of the feed being used."
Pseudopregnancy is a condition in which a sow has a delay in the normal
estrus cycle. During this time the sows present signs of pregnancy
without ever delivering.
Numerous things can cause the pseudopregnancy problems.
"It is fundamentally people," Carr said. "They believe a sow to be
pregnant when she's really not."
He also attributed the problems to "boars being overused, sows being
moved too often or sows being too lean due to outdoor units."
Another possible cause of pseudopregnancy is the presence of
estrogen-like compounds called mycotoxins that are produced by the
fungus Fusarium.
According to researchers, zearalenone is the mycotoxin that is most
commonly associated with pseudopregnancy.
Samples of feed corn were taken and tested from all of the farms.
Fusarium molds were found, but none of the corn samples contained any
detectable zearalenone.
"It's been known for many decades that Fusarium infection is very
common in corn kernels," Munkvold said. "However, the presence of
Fusarium does not necessarily mean that mycotoxins are present at
harmful concentrations."
Carr said Fusarium is "a little like moldy bread. It is normally a storage
issue."
To resolve issues on the farms in question the researchers looked at
reproductive problems that "are typical on a day to day basis," Carr said.
"Detailed examinations of breeding management programs" helped
explain the problems on three of the five farms. One of the farms fixed
the problems prior to the investigation. The fifth farm closed due to
economic reasons.
"It was disappointing to me personally to not have been able to solve his
problems," Carr said of the fifth farm. "There are still unanswered
questions."
A formal report about the investigation is expected to be published later.
Source: Iowa State Daily