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Science Update
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| Starter Diets Hike
Weanlings' Health
When piglets can no longer get their mothers' milk, most swine producers feed
them an expensive protein that helps relieve their stress and prevent illness.
Diets of most early weaned pigs now include this protein. Researchers hope that
by learning how the plasma protein works, it will be possible to make improved
feed additives that are even more effective and yet less expensive.
Scientists are studying the immune systems of pigs that have been fed
spray-dried plasma. They want to find cost-effective ways for swine producers
to raise healthier pigs that eat heartily and quickly produce plenty of pork
from each pound of feed. They have already observed that immune-challenged pigs
fed the spray-dried plasmas were better able to resist infections during the
week after weaning. The work has been awarded the National Pork Producers 2000
Award for Innovative Basic Research.
Jeffrey A. Carroll,USDA-ARS
Animal
Physiology Research Unit, Columbia, Missouri; phone (573) 882-6261.
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| Teaming With Brazil To
Quell Dengue Virus
Dengue, transmitted primarily by the yellow-fever mosquito, Aedes
aegypti, causes a severe, flulike illness. It has re-emerged around the
world in recent years, reaching epidemic proportions in Brazil and other parts
of the world, according to the World Health Organization. WHO estimates that
there may be 50 million cases of dengue worldwide each year. |
| The A. aegypti
mosquito has been largely eliminated from the United States and is now confined
to the southernmost areas of Florida and Texas. But dengue is endemic in more
than 100 other countries.
U.S. and Brazilian government officials have pledged to conduct a joint
research project to develop means to control the A. aegypti mosquito.
Under the agreement, scientists will use a biological control agent called
Edhazarda aedis, a microsporidium. This single-celled parasitic
microorganism attacks and kills only the mosquito. In the mid-1990s,
small-scale U.S. field trials using E. aedis were successful. Now
researchers are planning small-scale trials in three areas of Brazil later this
year, followed by large-scale releases of the organism to control A.
aegypti.
Donald Barnard,
USDA-ARS Center for Medical, Agricultural,
and Veterinary Entomology, Gainesville, Florida; phone (352) 374-5930.
Shellac Shines on Citrus
The shine that helps fruits glisten on the local produce stand may soon be only
the most visible manifestation of a more natural way to preserve
fruit—some 34 million tons of it—while on its way to market. New
fruit coatings are being made from reformulated shellac and sucrose ester, a
compound derived from combining sugar with a fatty acid. These biocoatings help
maintain quality by promoting the growth of beneficial bacterial and yeast
populations naturally present on the fruit.
Chemicals commonly used to preserve harvested fruit are relatively costly and
have been found to kill beneficial microorganisms. Tests with reformulated
shellac and sucrose ester show that not only do these coatings support growth
of some helpful bacteria and yeasts, they also appear to prevent development of
off-flavors in fruit by allowing for a better gaseous exchange of oxygen and
carbon dioxide than commercial chemicals permit.
Raymond G. McGuire, USDA-ARS
Subtropical
Horticulture Research Station, Miami, Florida; phone (305) 254-3641.
Forensic Pathologists Probe the Past for Potato Blight
To learn more about the sources of Phytophthora infestans—the
fungus that started late blight epidemics in potato crops in Ireland in
1845—scientists have studied genetic material from more than 60 herbarium
samples. They are looking at samples from Europe and North America and from
sources such as the National Fungus Collections in Beltsville, Maryland.
To see what fungi might be present, the researchers developed primers using
polymerase chain reaction (PCR) technology to specifically amplify DNA from
plant samples. PCR can reproduce millions of copies of the unique segments of
fungal DNA that occur in a plant tissue sample. It lets researchers quickly
distinguish among pathogens according to the specificity of the PCR
amplification. No longer do they have to isolate fungi from diseased roots or
leaves and spend days culturing them for identification. Rapid DNA
identification of offending microbes would quickly tip growers off to the need
for control measures before fungal diseases could seriously curtail yields.
So far, 20 specimens have tested positive for P. infestans, including
one from Ireland collected in 1846 and others from Britain collected in 1845,
1846, and 1847. Molecular studies of herbarium specimens from the past could
open a new window to understanding and preventing future epidemics.
Carol L. Groves, USDA-ARS
New England Plant, Soil,
and Water Laboratory, Orono, Maine; phone (207) 581-3267.
"Science Update" was published in the
August 2000
issue of Agricultural Research magazine.
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