Mad cow outbreak may have been caused by animal rendering plants
N.Y. Times News Service Mar 11, 1997
When cows in Britain began staggering around and dying, their brains
eaten away by a mysterious disease, officials in the United States were
reassuring. The disease would not be a problem here, they said. Later,
when it appeared that a few people in Britain had contracted a similar
lethal condition from eating affected meat, experts at the Department of
Agriculture said there was no reason for Americans to worry.
Now, though, the Food and Drug Administration is starting to talk about
new regulations in the aftermath of disturbing hints that something similar
conceivably could appear in American animals. So far, the only affected
animals are a few hundred mink in Wisconsin. Nevertheless, the agency wants
to restrict the little-known agricultural practice that lies behind the
problem in Britain: the use of rendered animal tissue in animal feed. In the
process, they are drawing new attention to rendering -- the ancient but
seldom-discussed practice of boiling down and making feed meal and other
products out of slaughterhouse and restaurant scraps, dead farm animals,
road kill and -- distasteful as it may seem -- cats and dogs
euthanized in some animal shelters.
This quasi-cannibalism lies behind the outbreak in Britain and regulators
want to be sure it will not cause problems in the United States. The disease
that struck the British cows, bovine spongiform encephalopathy, may have
originated as scrapie, a mysterious condition limited to sheep. Scientists
believe the so-called mad cow disease results when cattle eat feed made from
the brains or spinal cords of sheep suffering from scrapie. They believe the
people who died were infected when they ate beef or other products from
these cows, a theory that remains controversial, though evidence is
accumulating.
Public health officials and agricultural experts say there are good
reasons to believe that mad cow disease will not become a problem in the
United States. Scrapie is less common in this country than in Britain. More
importantly, the Food and Drug Administration is moving to ban the use of
certain animal tissues in cattle feed. The agency recently held hearings on
the effects that such a ban might have on the billion-dollar industry and
hopes to decide this year whether to impose a ban.
Rendering, which dates to the early Egyptians, operates in the shadows of
polite society, persisting because it provides an essential service:
disposing of millions of pounds of dead animals every day.
"If you burned all the carcasses, you'd get a terrible air pollution
problem," said Dr. William Heuston, associate dean of the Virginia-Maryland
College of Veterinary Medicine at College Park, Md. "If you put it all into
landfills, you'd have a colossal public health problem, not to mention
stench. Dead animals are an ideal medium for bacterial growth."
Renderers in the United States pick up 100 million pounds of waste
material every day -- a witch's brew of feet, heads, stomachs,
intestines, hooves, spinal cords, tails, grease, feathers and bones. Half
of every butchered cow and a third of every pig is not consumed by humans.
An estimated six million to seven million dogs and cats are killed in animal
shelters each year, said Jeff Frace, a spokesman for the American Society
for the Prevention of Cruelty to Animals in New York City.
For example, the city of Los Angeles sends 200 tons of euthanized cats
and dogs to West Coast Rendering, in Los Angeles, every month, according
to Chuck Ellis, a spokesman for the city's Sanitation Department. Pet food
companies try not to buy meat and bone meal from renderers who grind
up cats and dogs, said Doug Anderson, president of Darling International
Inc., a large rendering company in Dallas. "We do not accept companion
animals," he said. "But there are still a number of small plants that will
render anything."
At least 250 rendering plants operate in the United States, said Bruce
Blanton, executive director of the 130-member National Renderers Association
in Alexandria, Va. While there are still a few small operations on the
outskirts of some cities, he said, modern rendering plants are large and
centralized, and the industry's revenues amount to $2.4 billion a year.
After trucks deliver the wastes to the plants, the material is minced and
fed into a vessel where it is steam-cooked to 250 degrees or more, and then
the stew is cooked for 20 to 90 minutes, Blanton said. In the resulting
mash, heavier material drops to the bottom and the lighter stuff floats to
the top. Fat is siphoned off the top, filtered and sent through centrifuges
to further refine it, Blanton said. Chemical manufacturers turn much of it
into fatty acids for lubricants, lipstick, cement, polish, inks and waxes.
Other fractions, including gelatinous layers, tallow and grease, go into
thousands of products, including soaps, candles, pharmaceuticals,
homeopathic medicines and gummy candies.
The heavier protein material on the bottom goes through a separate
process, Blanton said. It is dried, squeezed to remove more fat and dried
again. The resulting powder is the major ingredient in pet and animal
feed. It is a cannibalistic practice that has proved highly profitable.
"We are the original recyclers," said Dr. Don A. Franco, a veterinarian
and director of scientific services for the Animal Protein Producers'
Industry, another trade group representing rendering firms. "We recycle
40 billion pounds of material a year."
Mad cow disease erupted in Britain because of a number of factors there,
said Dr. Linda Detweiler, a veterinarian with the United States Agriculture
Department's Animal and Plant Health Inspection Service in Trenton. Unlike
the United States, Britain has a large sheep population relative to cows and
a serious problem with scrapie, a transmissible, slowly progressive
degenerative brain disease of sheep.
Many scientists who have studied the problem now believe that scrapie
somehow crossed a species barrier to infect cows, possibly when the cows ate
feed composed in part of brain tissue from infected sheep. The disease
presumably jumped to people who ate infected cow brains. Current theory
holds that some people may have genes that make them particularly
susceptible.
Mad cow disease was first recognized as a cattle disorder in November
1986. Since then more than 165,000 cows have been affected. Heuston said
renderers were shocked to learn that an agent like scrapie might survive the
rendering process.
But British rendering practices may have helped spread the disease, said
David Evans, president of Carolina Byproducts, a rendering company in
Greensboro, N.C. There are people in Britain, called knackers, who make a
living going around the countryside picking up dead animals and rendering
them in their backyards. The fat they obtain brings good money from chemical
firms, he said.
These knackers simply grind up and partly cook their daily haul to break
fat cells and collect the gunk from the top of their vats. The remaining
material, called greaves or crackling, was sold to farmers who then mixed it
with grain and fed it to their animals. This material, some derived from
sheep with scrapie or cattle with mad cow disease, was fed in large amounts
to dairy herds in the late 1980s, Detweiler said.
Yet another factor lay in the way greaves were processed in conventional
rendering plants, Anderson said. Until the early 1980s, many renderers had
used flammable solvents to dissolve fats and the solvents may have
deactivated the agent that causes mad cow disease and scrapie. But after
several plant explosions, the companies switched to other methods that
appear not to deactivate the agent -- a mysterious particle called a prion.
Since 1989, British renderers have tried to keep infected meat out of
their products, many knackers have gone out of business and brains are no
longer put into hamburger. But the incubation for the human disease is 7 to
30 years, Evans said. While only 15 cases of human disease have been
confirmed, many experts fear a latent epidemic.
In 1989, the American rendering industry initiated a voluntary program
under which, for example, no sheep heads were to be accepted at rendering
plants. An Agriculture Department survey three years later found that 6
of 11 plants inspected still did accept sheep heads. Nevertheless, many
experts feel that American shores are safe from mad cow disease, especially
if scrapie is the underlying vector. In Britain, sheep account for 14
percent of raw rendering material. Here it is 0.6 percent and most of that
material is free from scrapie.
The reason is that scrapie is closely monitored by United States
Agriculture Department veterinarians under a federal program. There are no
knackers in this country and no greaves to infect cattle, Detweiler said.
Few ranchers here feed meat and bone meal to young cows and American
renderers usually treat the raw material at higher temperatures.
But the key element in efforts to prevent the cow disease is a newly
proposed Agriculture Department ban on feeding protein derived from ruminant
animals to other ruminants. Ruminants are animals that chew cuds, including
cows, sheep, goats, deer and elk. Mink are included in the ban because they
can be affected by a disorder similar to mad cow disease.
If the Agriculture Department rules are adopted, cow protein might still
be fed to fish, chicken or pigs in hope that if mad cow disease were
to appear, a species barrier would stop it from spreading. At the same time,
the Agriculture Department continues to monitor American cows for signs of
mad cow disease. Scientists have examined the brains of 5,342 cows that
displayed symptoms of central nervous system disease; no cases have been
discovered.
But a major reason to worry is that the cow epidemic may have nothing to
do with scrapie or the processing techniques used by renderers, said Dr.
Richard F. Marsh, a veterinarian at the University of Wisconsin in Madison.
There are reasons to believe that mad cow disease has already risen
spontaneously in American cattle, he said. But it apparently has not jumped
into the animal feed supply at this point.
The strongest evidence is an outbreak of mink encephalopathy (a disorder
similar to mad cow disease) that occurred in 1985 in Stetsonville, Wis. The
mink farmer did not feed commercial meal to his animals, Marsh said. Rather
he fed them the meat from a downer cow, a cow that is down and cannot get
up. It is possible that the cow had a spontaneous case of mad cow disease
and passed it into mink, Marsh said.
Spontaneous cases of mad cow disease may well occur in one cow out of
every million cows each year, said Dr. Joseph Gibbs, a leading expert on mad
cow disease at the National Institute of Neurological Disorders and Stroke
in Bethesda, Md. There are 150 million cows in this country, which means
that each year 150 of them might develop mad cow disease -- all on their
own, without any exposure to tainted feed.
Renderers pick up the carcasses of 100,000 downer cows every year
and mix them in with other animals, Marsh said. Although the Agriculture
Department tries to test downer cows for signs of mad cow disease, it can
only sample a small percentage. Moreover, animals can be quite sick and not
show signs of it before they are sent to slaughter, Marsh said. Thus, try as
they might to avoid the problem, renderers could unknowingly introduce
infected animals into animal feed and start an epidemic.
Deer and elk also have a spontaneous mad-cow-like disease, Gibbs said. If
they die in the woods, the disease would not be transmitted. But if they are
killed on the road, they are sent to zoos or greyhound tracks or, more
often, go straight to the rendering plant to end up as cattle feed or pet
food.
treif
meat | kosher meat | mikvah | kosher slaughter
![[Under Construction]](images/undercon.gif)
