Nutrition and Immunity: Looking for
A strong immune system can make the
difference between fighting off a passing virus or succumbing to illness. It
can mean higher milk production, healthier offspring and better growth. But how
can producers help strengthen their animals immunity?
Researchers at several ARS laboratories are
working to find out. The scientists focus on the links between nutrition and
immune function, because feed-based strategies are some of the most practical
for producers to implement. In addition, these strategies offer a rapid means
of getting newer scientific principles of animal health from the laboratory
into the hands of producers and extension agents.
Some links between nutrition and disease
are direct. For example, ARS researchers at the National Animal Disease Center (NADC) in Ames,
IA, showed that high potassium
levels cause milk fever in cows--not calcium as previously thought.
More often, though, immunity and nutrition
have less tangible connections. While immune function appears depressed in
dairy cattle just before and after giving birth, the reasons are not well
In beef cattle, researchers at the
Growth Biology Laboratory in Beltsville,
MD, discovered several years ago that
diets curbed an overproduction of cytokines observed with poor or
unbalanced nutrition. While cytokines are necessary hormones, overproduction
can cause shock and cardiopulmonary failure.
More recently, Beltsville researchers found
that changes in metabolic hormones and cell processing of specific nutrients
interplay to regulate the amount of chemically active free radicals
produced in cells. These free radicals can change the activity of otherwise
normal proteins and, in turn, alter metabolism and increase the rate at which
healthy cells deteriorate. Antioxidant vitamins can reduce free radical impact.
Ongoing studies will help define the best mix of antioxidants in cattle feed
during anticipated periods of stress, such as birth, weaning, or turning out to
pasture in the spring.
ARS ability to hold animals long term
helps researchers study these complex interactions. For instance, NADC
scientists can infuse dairy cattle with nutrients and perform sophisticated
blood assays while maintaining them in the milking barn. Thats crucial
for understanding the immune system changes that take place immediately before
and after cows give birth. The Ames location also has quarantine facilities and
a veterinary staff available to handle disease research.
At Beltsville, researchers can team with the
Nutrient Conservation Laboratory and
perform indirect whole body calorimetry on cattle. This allows them to monitor
whole-body oxygen consumption and oxidation as a function of changing nutrient
composition and response to simulated disease stresses.
At the Aquatic
Animal Health Research Laboratory in Auburn, AL, ARS scientists are
expanding their disease and parasite studies to define the effects of
nutrition, feed and feeding on immunity and disease resistance in fish. They
hope to develop feeds that optimize not only growth and feed efficiency but
also for improving the health of catfish and other warmwater aquaculture
ARS has recently restructured its national
programs. The animal nutrition component now resides under
For more information, contact:
Beltsville, MD (beef cattle)
Ames, IA (dairy cattle, periparturient
Auburn, AL (fish)
A new, ARS-developed laboratory method for growing macrophages in
tissue culture may help researchers studying the virus that causes porcine
reproductive and respiratory syndrome. The virus replicates inside
Special ARS chicken breeding lines--developed
with varying degrees of genetic resistance to viral-induced lyphoid tumors--are
now stored in Fort Collins, CO, and East Lansing, MI, as the first accession in
ARS National Animal Germplasm Program.
Substantially more nutrients from silage should
be available to dairy cattle in the Southeast, thanks to a
new corn germplasm
line with improved digestibility released by ARS.
ARS and University of Arkansas scientists have
selectively bred four generations of
chickens with low or
high resistance to ascites, a fatal heart condition. By defining the
differences between the two groups, they hope to find a treatment or cure.
ARS researchers discovered leptin in
chickens using a new technique. The protein regulates appetite and energy
The International Chicken Genome Mapping
--in which ARS partici- pates--released its
latest draft of the
chicken genome map. This map could help breeders increase disease
resistance and lessen dependence on antibiotics.
Hay made from
selenium-enriched canola may provide a new source of the essential nutrient
selenium for livestock raised in deficient regions while cleaning up soil and
water overloaded with this mineral.
These ARS researchers have been honored recently
for their achievements:
USDA Honor Awards:
Laboratory Consortium Awards for Excellence in Technology Transfer:
David Swayne , Michael
Perdue, David Suarez, Stacey Schultz- Cherry, Joan Beck, Patsy Decker, and
Roger Brock, Southeast Poultry Research
Laboratory, for research leading to advanced understanding of the
pathobiology and epidemiology of Hong Kong H5N1 avian influenza and development
of strategies to protect U.S. poultry from this disease.
H. Ray Gamble ,
Parasite Biology and Epidemiology
Laboratory, for testing and promoting a new system for certifying pigs at
the farm as free of Trichinella and other parasites.
Katherine I. ORourke and
Donald P. Knowles, Jr.,
Animal Disease Research Unit, for diagnostic
tests to detect scrapie in live animals, piroplasmosis in horses, and
anaplasmosis in cattle.
Grains & Potato Germplasm Research Unit, for developing low-
phytic-acid corn, which provides phosphorus in an easily absorbed form for
Ralphs, Poisonous Plant Research Laboratory,
was presented with an Outstanding Achievement Award by the Society for Range
Management for developing strategies to control poisonous rangeland plants,
including aversion conditioning for training large animals.
Great Plains Research Laboratory, received an Outstanding Achievement Award
by the Society for Range Management for developing improved forage