It's a pretty safe bet you won't hear this request from your kids: "More
liver, please." If you do, however, there will be no shortage of the
iron-rich delicacy most kids love to hate thanks to a vaccine developed
by Kansas State University professors.
T.G. Nagaraja, a professor of diagnostic medicine and pathobiology in
K-State's College of Veterinary Medicine, and M.M Chengappa, university
distinguished professor of microbiology and department head of
diagnostic medicine and pathobiology, have developed a vaccine that
prevents liver abscesses in cattle. The vaccine was recently given
approval by the United States Department of Agriculture.
The KSU Research Foundation and Schering-Plough, a global science-based
health care company, have a licensing agreement to market the vaccine.
Schering Plough Animal Health corporation further developed the product
and worked with USDA to get license approval for the vaccine.
According to Nagaraja, abscesses are a common malady found mostly in
grain-fed cattle, the result of an aggressive feeding program. He said
about 20 to 40 percent of the grain-fed cattle in feedlots are afflicted
with abscesses, which cannot be detected until the animals are
slaughtered. While the organ is condemned and not used, in most
instances the remainder of the carcass is approved for sale.
"If you look at the animal you can't tell if they're abscessed or not,"
Nagaraja said. "They look normal, so they don't show any clinical signs.
The only time we see the problem is when animals are slaughtered."
The abscesses are caused by bacteria present in the rumen, the first of
four compartments that comprise a cow's stomach. That compartment
contains numerous microorganisms beneficial in assisting the animal
digest food. According to Nagaraja, who began researching the vaccine 14
years ago, the liver is a very well defended organ. So much so that he
calls it the "Pentagon" because it has "so many systems" of defense.
However, under certain conditions, when this bacteria crosses the
stomach wall and gets into the blood stream, it is trapped inside the
liver, producing a toxin that kills white blood cells or leukocytes,
which generally defend the body from germs or infections.
The vaccine prevents abscesses from occurring by neutralizing the toxin,
a protein. Once injected into the animal, antibodies are produced that
act on the protein. When the bacteria goes into the liver and produces
the toxin, antibodies neutralize it and allow the leukocytes to survive.
These white blood cells can, in-turn, kill the bacteria.
"That's not a new concept; it's been done with other bacteria," Nagaraja
said. "But it was new for this organism that we were able to identify
strains that are able to optimize conditions for production of large
amounts of leukotoxins."
According to Nagaraja, abscesses are a significant economic liability to
producers, packers and consumers. He said the liver condemnation, which
he estimates to cost about $5 per head, is just one of the economic
losses of this disease. Occasionally, the entire carcass must be
condemned because the abscess in rare instances causes adhesions to
other organs or ruptures, spilling pus into other organs.
Economic impacts may also include reduced feed intake, reduced weight
gain, decreased feed efficiency and decreased carcass yield. According
to Nagaraja, reduced animal performance is the major economic impact of
the problem. — WLJ