##################### Bovine Spongiform Encephalopathy #####################
What happens when Bossy dies?
January 23, 2005
By Andrew Barker
It may sound morbid, but with rendering plants disappearing, more
farmers are looking to composting
What do you do with a dead cow?
It's not a theoretical question in many parts of Vermont. "Deaths come,"
says Teddy Yandow, a dairy farmer in St. Albans. He says he loses a
couple of cows every year out of his herd of 85 milkers. "You've just
got to expect it."
Indeed, nearly 300,000 cattle currently live in Vermont, and according
to Marie Caduto, an agricultural resource specialist with the state
Natural Resource Conservation District, about 4.3 percent of those
animals die every year. That translates to about 16,000 cows.
So, what do you do with 16,000 dead cows?
Well, if you're looking for a low-cost, environmentally sound method of
disposal, composting might just be the answer. It's catching on with
farmers across the state who recognize the elegance and simplicity of
putting bacteria to work on their dead animal carcasses.
Yandow is one of them. "I started composting manure," he says, "and then
I had a cow die, and I thought, 'Well, I'll bury her in the compost and
see what happens.'" He opened up a hole in the compost with a front
loader, laid the cow inside, and waited. A year later, the cow was gone,
except for a few of the largest bones. Ever since, Yandow's been
composting all his mortalities while perfecting his technique to make
the decomposition process work more efficiently.
"It's pretty amazing," says Brian Jerose, co-owner of Waste Not Resource
Solutions, a consulting business in Enosburg Falls, who trains farmers
and other professionals in composting techniques. "You can make a large
animal disappear in a pile of wood chips, waste feed and manure. Just
about any animal can be composted rabbits, turkeys, chickens, cows,
horses, pigs, sheep, goats, anything." In Vermont, operations as diverse
as Misty Knoll poultry farm in New Haven, the Champlain Rabbitry in West
Haven, and the 1,200-cow Blue Spruce Farm in Bridport are giving it a try.
Although composting has been around for a long time, it is only in the
last five years or so that it has been seen as a safe and viable way to
handle animal carcasses on the farm. John Brabant, an environmental
analyst in the Vermont Department of Environmental Conservation says:
"We've come to find that you can compost whole animals and offal from
the slaughtering process as readily as vegetable matter. You build the
piles a little differently, but the principle is the same."
In a brochure Caduto prepared for the NRCD, farmers are instructed to
compost animal carcasses by burying them with a front loader in the
center of a large pile of wood chips, waste feed, or other high-carbon
organic matter. It's remarkably simply in concept. And as long as the
pile has the right amount of moisture and enough space for oxygen to
flow through, decomposing bacteria get right to work and consume the
entire animal in a matter of months. The pile never needs to be turned.
"There's quite a chimney effect because a lot of heat gets generated by
the bacteria," Brabant explains. "The pile constantly draws fresh air in
from the bottom, and the organic material on top acts as a biofilter.
It's amazing. There's very little odor."Richmond farmer David Conant has
been composting his mortalities at Riverside Farms, where he milks 300
cows, for the last couple of years. "We use a combination of straw and
sawdust that is fairly moist, along with waste feed," he says. "It was
trial and error to get the combination right." But now that he has
refined his technique, he has composted about 15 cows and an equal
number of calves. "They need to be disposed of properly and this is a
proper way to do it. It works very well. After three to four months,
when we pick the pile up, there's just a few bones left, maybe the size
of your forearm."
No one is sure how many Vermont farmers are using the disappearing
carcass trick, but according Jerose, the number is in the hundreds.
"There has been an increase in adoption over the last two years," he
says. "I wouldn't be surprised if it's half of the farmers out there."
Decades ago, most dead animal carcasses in Vermont were destined for
rendering plants. As recently as the 1980s, renderers paid farmers for
the privilege of hauling away deadstock to be cooked down into meat and
bone meals, nutritional fats, and tallow. These were valuable
ingredients for a wide variety of pet food products, livestock feeds and
other marketable items. In fact, in a tidy cycle, feeding high-protein
rendered deadstock remains back to livestock became a common practice in
the dairy and beef industries. But price pressures in the rendering
industry forced companies to begin charging farmers for hauling
deadstock away in the early 1980s.
Then, the discovery of bovine spongiform encephalopathy, also known as
mad cow disease, in European cattle in the mid 1980s kicked the bottom
out of the market for many rendered products. Since the continuous
rendering process used in most of the United States does not reach high
enough temperatures to deactivate the contagious agents in BSE, known as
prions, the safety of rendered feed products was called into question.
Other forms of transmissible spongiform encephalopathy, such as scrapie
in sheep and goats, were also a concern. "Buyers of these rendered
products were very concerned that they were buying a problem," says Carl
Cushing, director of food safety and consumer protection in the Vermont
Agency of Agriculture. Many farmers stopped feeding rendered products to
their animals, and in 1997, federal regulations banned the practice of
feeding rendered products made from mammals back to ruminants.
The result was a "constant and steady decline in the availability of
rendering," says Cushing. "And unless something changes, unless we find
a new value for this product, we won't see any improvement," Cushing
adds. Today, there are only 150 independent rendering plants left in the
United States, and only two of these companies pick up dead stock in
Vermont. Baker Commodities, with a processing facility in Ellenburg,
N.Y., serves the northern half of the state, and Bishop's Rendering in
Argyle, N.Y., picks up in some areas in southwestern Vermont.
In short, rendering dead animals has become an expensive proposition for
many Vermont farmers, and flat out impossible for others. Cushing
estimates that no more than 2,500 Vermont cows were sent for rendering
in 2004. "It's a tremendous service," he says. "They have terrible
overhead, they have to drive a long way, it's a perishable product. But
it's difficult for farmers to pay $75 per cow."
Pat Hayes, who milks 70 cows at Hayes Farm Inc. in Enosburg, agrees.
"Sometime last winter, I decided that the cost of getting rid of
carcasses was getting too expensive. It's gone from nothing to $20 to
$50 and then $75 a head. That's a little too pricey." Hayes turned to
composting his dead animals with chipped Christmas trees, which has
proven to be an economical solution. "All of the materials are pretty
much free," he says, and his time investment is small. He says he
doesn't even think a recent decline in hauling fees will tempt him to
call the rendering company to take away his mortalities. A Cornell
University study pegged the cost of composting a dairy cow carcass at
$37, including equipment costs, labor, and materials. Compared to
rendering fees, it's a bargain.
At The Royal Butcher in Braintree, Royal Larocque is eager to begin
composting the byproducts of his slaughtering business, which he says
will significantly lower his operating costs. While he waits for a state
permit, which is required for off-site composting, he is still spending
$20 to $22 per barrel to have offal picked up and hauled away by Baker
Commodities. When he opened the butcher shop less than two years ago,
hauling fees were only $12 a barrel. "Now, if we have a busy week, we
can end up with 12 barrels," he says. "I've spent $3,000 to $4,000 on
rendering and hauling fees since late last fall. When we get the
composting started, it's going to be quite a savings."
In a curious sort of way, a little help for farmers in the face of
higher rendering fees has come from the federal government, which now
analyzes brain stem tissue from dead cows to test for signs of BSE. Dr.
Kerry Rood, the Vermont state veterinarian, said his office collected
approximately 215 brain stem samples "on-farm" in 2004 and sent them off
to be analyzed for the U.S. Dept. of Agriculture. Farmers who
participate in the program are reimbursed $75 for the disposal costs of
the rest of the animal. The same program has also benefited rendering
companies, who contributed nearly 800 brain stems to Vermont authorities
last year. But a few thousand federal dollars for a testing program
cannot make up for lost markets in the rendering industry.
Another boost to the popularity of composting animal remains came,
strangely enough, from the devastating epidemic of foot-and-mouth
disease that swept across the United Kingdom in 2001. Over a period of
32 weeks, the highly contagious illness affected sheep, swine, and
cattle on over 2,000 farms. The epidemic was only halted after 6 million
animals were slaughtered.
"People started to wonder, 'What if it happened here?'" says Caduto at
the NRCD. "What would be the best way to dispose of all these animals?"
Experts in Britain had struggled with the same question. There,
rendering facilities were unable to handle the tremendous volume of
animal carcasses, and officials were loathe to transport possibly
infectious animals to off-site rendering plants. Burning animals in open
pyres raised concerns about air pollution and created an environment of
despair among farmers and the public.
Composting emerged as a viable solution. Studies at Cornell, Iowa State
University and Kansas State University, among others, showed that
composting animals with corn silage, cornstalks, manure and straw could
be an "effective biosecurity technique" in response to a large-scale
livestock disease outbreak. The heat generated by the process of
decomposition can kill most disease-causing bacteria and viruses in a
matter of days, including salmonella, E. coli., and the virus that
causes foot and mouth disease.
Also critical in response to an emergency, composting allows large
numbers of animals to be processed at once, as long as high-carbon
bulking materials are available in sufficient quantity. The state of
Maine has drafted a statewide emergency plan that instructs farmers to
compost animals in stored feed and municipal biosolids in the event of
an emergency, according to Jerose.
On-farm animal composting may also be a valuable tool to prevent a
widespread outbreak of livestock disease in the first place. "By
composting animal mortalities, farmers can avoid the biosecurity risk of
having the dead animal hauler come onto the farm," says Julie Smith,
dairy specialist at the University of Vermont Extension Service. "These
folks may not be following the best biosecurity principles, such as
wearing clean boots at every farm." By the same token, animals that die
from contagious diseases have little chance of affecting other farms if
they are composted on site. "The farmer has very low risk in terms of
handling the animal himself," she says.
Of course, composting is not the only alternative disposal method for
animal mortalities that has been tried over the years. Many farmers
still bury dead animals on their property. When carefully done on an
appropriate site, it is a safe and practical option. But it can also
present problems in poorly drained areas or during wet years. "When you
dig a hole today to bury an animal, it could be half full of water in
April," says Caduto. "That cow could be sitting in your groundwater."
Brabant likens the situation to a failed septic system in its potential
health and environmental impacts.
The "Back 40" method of carcass disposal is still being practiced in
Vermont as well. Brabant says on some farms, dead animals are "displayed
on the back stone wall. Usually the neighbors are not too happy with that."
"Farmers say, 'Coyotes clean it up in a week,'" Caduto offers. "But what
we're really doing is breeding better coyotes. And if they get used to
the idea of getting food at farms, then we'll have a problem with them
taking lambs." Beyond that, she says, allowing scavengers to dispose of
animal carcasses can present biosecurity problems. "If that cow was sick
in any way, you could be spreading diseases."
In other parts of the country, a surprising range of other alternatives
are also under consideration for disposing of animal carcasses. A 2004
National Agricultural Biosecurity Center study publication discussed no
less than 16 methods of disposal including alkaline hydrolysis, in which
carcasses are chemically transformed into a "sterile, coffee-colored
alkaline solution"; ocean disposal; and refeeding to alligators or other
predators. But in a head-to-head analysis, composting comes out on top
as one of the least expensive, most reliable and safest ways to handle
animal carcasses. "We're trying to encourage as many farmers as we can
to manage carcasses better with composting," says Brabant.
Pitfalls and promises
In some circles, among sustainable agriculture advocates and experts,
composting is on a level with duct tape and blow torches for its
usefulness around the farm. "I hear some farmers, when they're going to
a meeting these days, make a bet as to how soon the word composting will
come up," says Vicky Viens, waste reduction specialist in the state
Department of Environmental Conservation.
In the case of animal composting, the applications are even reaching
beyond the farm. New York State has a program for road-kill deer carcass
composting, which keeps animals out of the landfill. Several years ago,
the Cornell University Paleontology Department even managed to compost a
northern right whale that had died on the New Jersey coast, leaving only
clean bones at the end of several months.
That doesn't mean that it's magic, though. All kinds of disasters await
the sloppy or uneducated farmer. Odor can be a huge problem. "If you
turn the pile," Brabant warns, "and the putrefied flesh hits the air, if
there are any neighbors around, you just blow 'em away." Similarly,
Smith at the UVM Extension cautions that if a pile fails to get enough
oxygen or becomes too compacted, "You're going to end up with a big,
At Brault's slaughterhouse in Troy, neighbors complained about odors
when the plant began composting its offal on-site three years ago. "I
was stirring it every week. I'd pick it apart and add stuff to it," says
owner Tony Brault, who gave composting a try when rendering costs became
prohibitive. The decomposition process was working fine, but the odors
were overpowering when the piles were disturbed. "It was a clear case of
this system going awry," says Brabant. Working with Jerose of Waste Not
Solutions, though, Brault learned to manage the process without turning,
and the compost piles and neighbors have apparently been coexisting
peacefully ever since.
Hayes, who farms less than a mile from Enosburg village, says he has
worked hard to avoid composting odors from the start. "Being that close
to town, there are other people in the equation," he says, "and I don't
enjoy that smell either."
Caduto sums up another possible problem with composting in one word:
January. "Trying to compost in 10 below can be pretty difficult," she
says. But not impossible. Jerose counsels his clients to make sure they
have a large, biologically active compost pile already working before
winter arrives. "The piles are self-insulating, so even if it's got a
crust of 6 to 12 inches of ice on the outside, there's heat on the
inside," he says. If the carcass itself is not frozen solid when it is
added to the pile, it will usually decompose without any problems.
Sometimes, though, the cold is too deep and truly prevents wintertime
composting. "Many people have seen the dead cow that can stand up on its
own because it's frozen stiff," says Jerose. When that happens, he
instructs farmers to bury the carcass in a large pile of wood chips and
wait until the end of the summer before moving the pile. "It won't be
actively composting until May at the earliest," he notes. "You're just
kind of storing it until it has a chance to thaw out."
Occasionally, a poorly built pile can attract scavengers, too. "That
usually only happens when people scrimp on the cover," says Caduto.
But when it's properly done, proponents say, composting animal
mortalities can be a beautiful thing. Abe Collins, who works with Yandow
on his dairy farm in St. Albans, says it keeps valuable nutrients on the
farm. "With composting, the residue of a cow's life cycle is stable
bionutrients in the form of a rich, black compost," he says. "It's a
sweet-smelling product that we can spread on the fields. Every now and
then you see a scapula fling out the back, but I don't know that the
cows know what it is necessarily when they come across it in the
fields." Collins says spreading the compost helps keep pasture quality
at a high level.
Viens stresses the economic benefits of composting. "Any time you're
capturing nutrients on the farm, you're improving the bottom line," she
suggests. "Compost can reduce fertilizer use by 50 percent, it provides
slow-release nutrients to the soil, and it holds onto water really well."
Caduto points out that composting also keeps dollars on the farm in a
more direct way. The money that farmers don't have to spend on rendering
fees stays in their pocket for another day. "If every cow carcass in the
state was sent to the rendering services, it would approach $1 million,"
she says. "That's a lot of money out of our farm economy."
Andrew Barker is a freelance writer who lives in Burlington.
> Livestock Mortalities:
> Methods of Disposal and Their
> Potential Costs
> The estimates of livestock mortalities used throughout this report are
> believed to not include most downer livestock, many of which are
> currently processed into human food at specialized slaughter facilities.
> The number of downer livestock in the US is unknown, but estimates put
> number as high as 1.5% of all cattle, or nearly 1.8 million cows per
> year (National Market Cow and Bull Audit).
> . Composting is an approved method of disposal in most states,
> although strict regulations are often in place regarding construction
> of the composting structure and the type, size, and amount of
> livestock that can be composted at a single location. These
> regulations can add to the management burden and expense of this
> method, often requiring the advice of extension agents or other
> professionals to ensure compliance. The concept can be described as
> burying the animal above ground in a mound of sawdust or other carbon
> source and allowed to decay. In the composting process, bacteria,
> fungi, actinomycetes, and protozoa break down the tissues of carcasses
> aerobically to produce water vapor, carbon dioxide, heat, and a
> stabilized organic residue. High temperatures indicate good microbial
> activity and will reach 120 to 160 degrees F, which is high enough to
> kill most pathogens, but far lower than the temperatures achieved
> through rendering. An internal pile temperature of at least 131
> degrees is needed for three days to destroy disease-causing organisms,
> though the resulting material is still not guaranteed to be pathogen
> free and the process would be incapable of destroying the BSE prion if
> it were present. Furthermore, maintaining the proper heat, moisture
> content, and C:N ratio is critical to minimize odors and diseases, but
> can be difficult under all but ideal conditions. Even under the best
> of circumstances, odors can be a problem. Thus, the process requires
> intensive management oversight. Facility site selection is also
> important to successful composting and to avoid environmental dangers.
> A site must be selected so that surface water and groundwater sources
> will not be polluted, and it is beneficial to locate the facility away
> from neighbors and human dwellings. The facility should be at least
> 100 feet away from production facilities to lessen the risk of disease
> transmission by rodents. The drainage of the site should be considered
> when deciding what type of compost facility to build. There should be
> no surface water contacting the compost area. Clean water diversions
> should be built to control runoff water. Given the potential for
> adverse environmental consequences, composting often requires
> additional time and equipment compared to the other disposal methods.
> To successfully operate a compost facility, a bucket loader or skid
> steer is needed to transport carcasses from buildings or lots to the
> compost facility, cover the carcasses, and move piles from the primary
> to the secondary stages. Equipment to haul and unload incoming carbon
> source is also needed. Finished compost can be spread on crop ground
> as a fertilizer source using a solid manure spreader, but if the BSE
> prion were present, this material would have to be disposed of by
> other means to ensure that the prion does not re-enter the food chain
> through plants grown where the compost was spread. Large animals such
> as mature cattle will often need to be cut into smaller pieces prior
> to being placed in the composting facility to ensure complete
> decomposition. And, the thick hides on mature cattle tend to be
> difficult to compost, requiring additional cycles to achieve complete
this process will NOT kill the TSE agent...
practice should he stopped...
Environmental Sources of Prion Transmission in Mule Deer
Michael W. Miller,*Comments
Williams, N. Thompson Hobbs,! and Lisa L. Wolfe*
*Colorado Division of Wildlife, Fort Collins, Colorado, USA; University
of Wyoming, Laramie, Wyoming, USA; and !Colorado State University, Fort
Collins, Colorado, USA
Suggested citation for this article: Miller MW, Williams ES, Hobbs
NT, Wolfe LL. Environmental sources of prion transmission in mule
deer. Emerg Infect Dis [serial on the Internet]. 2004 Jun [date
cited]. Available from:
Click to view enlarged image
Figure. Green forage growing at the site where a deer carcass infected
with chronic wasting disease had decomposed...
Prions cannot be directly demonstrated in excreta or soil. However,
CWD infectionspecific protease-resistant prion protein (PrPCWD)
accumulates in gut-associated lymphoid tissues (e.g., tonsils, Peyer
patches, and mesenteric lymph nodes) of infected mule deer (11,17
implicates alimentary shedding of the CWD agent in both feces and saliva
). Because PrPCWD
becomes progressively abundant in nervous system and lymphoid tissues
through the disease course (11
), carcasses of
deer succumbing to CWD also likely harbor considerable infectivity and
thus serve as foci of infection. We could not determine the precise
mechanism for CWD transmission in excreta-contaminated paddocks, but
foraging and soil consumption seemed most plausible. Deer did not
actively consume decomposed carcass remains, but they did forage in the
immediate vicinity of carcass sites where a likely nutrient flush (23
) produced lush
Our findings show that environmental sources of infectivity may
contribute to CWD epidemics and illustrate the potential complexity of
such epidemics in natural populations. The relative importance of
different routes of infection from the environment cannot be discerned
from our experiment, but each could play a role in sustaining natural
epidemics. Although confinement likely exaggerated transmission
probabilities, conditions simulated by this experiment do arise in the
wild. Mule deer live in established home ranges and show strong fidelity
to historic home ranges (24-26
). As a result of
such behavior, encounters with contaminated environments will occur more
frequently than if deer movements were random. Feces and carcass remains
are routinely encountered on native ranges, thus representing natural
opportunities for exposure. Social behavior of deer, particularly their
tendency to concentrate and become sedentary on their winter range, also
may increase the probability of coming into contact with sources of
infection in their environment.
The ability of the CWD agent to persist in contaminated environments for
>2 years may further increase the probability of transmission and
protract epidemic dynamics (8
infectivity in contaminated paddocks could not be measured, neither the
initial levels nor degradation rate of the CWD agent in the environment
was estimable. However, the observed persistence of the CWD agent was
comparable to that of the scrapie agent, which persisted in paddocks for
?1 to 3 years after removal of naturally infected sheep (7
between the CWD and scrapie agents suggest that environmental
persistence may be a common trait of prions. Whether persistence of the
BSE prion in contaminated feed production facilities or in environments
where cattle reside contributed to BSE cases in the United Kingdom after
feed bans were enacted (27
uncertain but merits further consideration.
Indirect transmission and environmental persistence of prions will
complicate efforts to control CWD and perhaps other animal prion
diseases. Historically, control strategies for animal prion diseases
have focused on infected live animals as the primary source of
infection. Although live deer and elk represent the most plausible
mechanism for geographic spread of CWD, our data show that environmental
sources could contribute to maintaining and prolonging local epidemics,
even when all infected animals are eliminated. Moreover, the efficacy of
various culling strategies as control measures depends in part on the
rates at which the CWD agent is added to and lost from the environment.
Consequently, these dynamics and their implications for disease
management need to be more completely understood.
Docket No, 04-047-l Regulatory Identification No. (RIN) 091O-AF46 NEW
BSE SAFEGUARDS (comment submission)
Docket No. 03-080-1 -- USDA ISSUES PROPOSED RULE TO ALLOW LIVE ANIMAL
IMPORTS FROM CANADA
Docket No. 2003N-0312 Animal Feed Safety System [TSS SUBMISSION]
[PDF] A Rapid Qualitative Assessment of possible risks to Public Health
Carcass Disposal: A Comprehensive Review
National Agricultural Biosecurity Center Consortium
USDA APHIS Cooperative Agreement Project
Carcass Disposal Working Group
> Mass burial
> and on-farm burial were last on the preferred
> method list due to the complicating matter of bovine
> spongiform encephalopathy (BSE) and the risk posed
> to groundwater (Hickman & Hughes, 2002).
> United States chronic wasting disease
> In February 2002, chronic wasting disease (CWD)
> was identified in whitetail deer in southwest
> Wisconsin. CWD is a transmissible spongiform
> encephalopathy (TSE). In order to control the
> disease, a 360-square-mile disease eradication zone
> and surrounding management zone were developed.
> All deer within the eradication zone were designated
> for elimination, and deer in the surrounding area
> were designated to be reduced. Many of the deer
> were destroyed by citizen-hunters, who were not
> destroyed by citizen-hunters, who were not
> permitted to use the deer for venison. Disposal
> methods were selected that do not endanger animal
> or human health or environmental quality. Selected
> methods had to be able to handle a large number of
> carcasses and comply with regulations. Cost was
> also a consideration, and it is anticipated that disposal
> costs will be one of the most significant expenses of
> the CWD control program. The four preferred
> methods used were landfilling, rendering,
> incineration, and chemical digestion (alkaline
> hydrolysis) (Wisconsin Department of Natural
> Resources, 2002).
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