Script: Statutory and Regulatory Requirements for Humane Handling, Part 3 (Stunning Methods)
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Hello and welcome. I'm Paul Koscak from FSIS and with me
today is Joan Collins to continue our discussion on the humane handling and slaughter
of livestock animals.
A program manager in our Office of Field Operations, Joan has been with FSIS for more than
20 years and has a great deal of experience training front line supervisors on the statutes,
Rules of Practice and the administrative enforcement process.
In our first two chapters, we covered the regulations and requirements of humane handling at the plant.
Today, we're going to talk about the four stunning methods acceptable under the Humane Methods of
Slaughter Act, which I'll just refer to from now on as the Act.
Joan, in an effort to provide some background information on the Act, could you tell us what
the statutory requirements are?
Well, basically, to meet the requirements of the Act,
before an animal can be shackled, hoisted, thrown, cast or cut, it must be rendered insensible to
pain. This can be done by a single blow or gunshot, or by an electrical or chemical method that
is rapid and effective. This applies to cattle, calves, horses, mules, sheep, swine and other livestock.
Stunning equipment must be maintained and in good repair. Equipment in poor repair can interfere
with the rapid and effective application of the stunning blow. If poorly functioning stunning
equipment results in inhumane treatment of animals, FSIS will generate a Noncompliance Record.
And, what are some examples of poorly maintained stunning equipment?
- leaking seals around carbon dioxide chambers;
- damp powder in captive bolt cartridges; and
- build-up of residue or debris in captive bolt barrels.
Other examples are:
- clogged gas ports in pneumatic captive bolt devices;
- leaking hoses or cylinders supplying pressurized air to pneumatic captive bolt devices; and
- corroded electrodes or switches.
So, proper maintenance of stunning equipment is very important. What
else makes stunning more effective or less stressful to the animal?
Proper restraint is also important. If an animal is not properly
restrained, it will be much more difficult to administer the stunning blow with a high degree
of accuracy. The stunning area should also be designed and constructed to limit the animal's
With any stunning method, it's important to observe the amount of time it takes for the animal to
begin bleeding out after being stunned. This bleeding out is commonly referred to as sticking.
Although there's no regulatory requirement for this time period, if the stun-to-stick interval is
prolonged, it could result in animals regaining sensibility on the bleed rail.
Joan, would you please elaborate now on the four stunning methods
acceptable under the Act?
Absolutely. The Act allows four stunning methods to be used in
slaughter operations. Each produces a state of surgical anesthesia in the animals, ensuring
that they feel no pain. The methods are:
- chemical - usually in the form of carbon dioxide;
- mechanical by use of a captive bolt;
- mechanical by gunshot; and
Okay, you mentioned chemical stunning. Whats that entail?
Chemical stunning involves carbon dioxide gas, which is approved
for rendering swine, sheep and calves unconscious, but is most commonly used with swine.
It must be administered to produce surgical anesthesia quickly and calmly, with a minimum of
excitement and discomfort to the animals.
Each plant must maintain a uniform carbon dioxide concentration in the gas chamber so that the
degree of anesthesia is constant to exposed animals. The gas concentration and exposure time,
also known as the dwell time, must be recorded graphically throughout each day's operation.
All gas-producing and control equipment must be maintained and in good repair, and all indicators,
instruments and measuring devices must be available for inspection by FSIS.
And, is there a special area in which this carbon dioxide is administered?
Yes. There are two types of gas chambers — the tunnel and the gondola.
The tunnel is open on both ends for entry and exit of animals. The gondola is designed for animals
to be lowered into a carbon dioxide pit and then raised after being anesthetized.
Once anesthetized, the animals are moved from the gas chambers and are ready to be shackled,
hoisted or placed on a table for bleeding.
As a note, carbon dioxide may also be administered to swine to induce death.
Is there a possibility that animals can recover from carbon dioxide?
Yes, there is. Animals can recover consciousness very quickly
after leaving the gas chamber. Therefore, plant officials need to bleed out the animals that
are not dead upon leaving the chamber very quickly to ensure that they don't regain sensibility to pain.
For plant employees, this means that they may need to spend more time observing animals throughout the slaughter process.
Now, the captive bolt stunning. Would you please explain this process
in more detail?
Essentially, there are two types of mechanical captive bolt stunners —
penetrating and non-penetrating. Both can be used to produce the immediate unconsciousness in
cattle, sheep, goats, swine, horses, mules and other equines.
Both types have gun-type mechanisms that fire a bolt or shaft out of a muzzle. The bolt is
discharged or propelled by a measured charge of gunpowder, usually a blank cartridge, or by
accurately controlled compressed air.
And both types must be operated by a well-trained and experienced plant employee. The employee
must be able to accurately and consistently position the stunning device so that the bolt hits the
skull at the right location to produce immediate unconsciousness.
The employee must also be able to adjust the air pressure or detonation charge when the sex,
breed or size of the animal changes. Charges suitable for smaller kinds of livestock such as
swine or young animals are not acceptable for use on larger kinds of older livestock.
What can a plant do to ensure that their stunning method is effective?
Well, some plants have adopted a practice of double knocking, where
the animals are stunned with two blows delivered in very rapid succession. The rationale behind
this procedure is that the consequences of an animal regaining consciousness are so severe that
plants want to ensure that it will not happen. The second blow is for security only.
What's important for the plant to keep in mind is that to meet the Act's regulatory requirements,
the first stun must be effective at rendering the animal insensible to pain.
You mentioned penetrating vs. non-penetrating captive bolt stunner earlier.
Would you elaborate on this, please?
Sure. The penetrating captive bolt stunner is typically powered by
compressed air and must have accurate, constantly operating air pressure gauges with consistent
air pressure. The gauges must be easy to read and conveniently located for inspection by FSIS.
When fired, the bolt in the penetrating captive bolt stunner penetrates the skull and enters the brain.
Therefore, it's important that the plant use either an adjustable device or different devices for
larger and smaller animals.
Plant personnel also need to remember they cannot use captive bolt stunners that deliberately inject
compressed air into the cranium at the end of the penetration cycle to stun cattle.
What's the difference between penetrating and non-penetrating captive bolt stunners?
The non-penetrating captive bolt stunner is similar to the penetrating bolt,
except that it has a bolt with a flattened circular head and is sometimes referred to as a mushroom
Some plants prefer to use this method to avoid the time-consuming task of physically removing large
blood clots, hair, bone, splinters and other debris from the brain.
Essentially, the animal becomes insensible from the acceleration concussion and sudden changes
in the intercranial pressure. Therefore, accurate placement of the stunning blow is very important
when using a non-penetrating captive bolt stunner.
Joan, you said there is another mechanical method to stun animals.
What is it?
Firearms can be used to stun cattle, calves, sheep, goats and swine.
The caliber of the firearm must be such that a single shot of a bullet or projectile into the
animal must produce immediate unconsciousness.
The correct caliber firearm, powder charge and type of ammunition used must produce the desired effect,
which is to assure uniform unconsciousness with every discharge.
If a small bore firearm is used, the only types of projectiles that can be used are hollow-pointed
bullets, frangible iron and plastic composition bullets, and powdered iron missiles.
The most important thing to remember is that the federal regulations mandate that every animal is
rendered insensible to pain by a single gunshot, regardless of the type of projectile used.
And, I believe you stated the fourth stunning method was electrical?
Yes, it is. Electric current is used for swine, calves, sheep and goats.
While approved for use in cattle, this is not a common practice. It's mostly used for swine.
Electric current must be applied with a minimum of excitement and discomfort to the animal, yet
strong enough to ensure surgical anesthesia throughout the bleeding operation. In addition,
the operator must control the timing, voltage and current so that each animal is properly stunned.
How does a plant administer electrical stunning?
There are two types of electrical stunning — one is head only
and the other induces cardiac arrest.
Head only stunning induces a gran mal epileptic seizure in the animal, yielding insensibility to pain.
When using this method, the stun-to-stick interval should not exceed 30 seconds.
Although this is not a regulatory requirement, this recommended timeframe will help assure the animal
does not regain consciousness.
And what is cardiac arrest stunning?
Cardiac arrest stunning induces both a gran mal epileptic seizure and
cardiac fibrillation in the animal — essentially, a heart attack.
This requires that the head must be stunned first or simultaneously with the heart, because stunning
the chest first would cause pain to the animal, not insensibility. And, this would be a violation of
I remember something about a variation on cardiac arrest stunning.
Would you tell us more about that?
Sure. You can also use a two-phase stun process. This is when the
electrical current is first passed through the head only, inducing insensibility, and then the
electrical current is passed through the heart, inducing cardiac fibrillation.
When using this method, it is important to accurately place the stunning wand on the body so
that the electrical current passes through the brain and/or heart.
If too much current is applied, hemorrhages or other tissue changes can occur that could interfere
with the inspection process. In addition, there might be damage to the capillaries, resulting in
multiple pinpoint hemorrhages in the muscle tissue.
Joan, thanks for giving us detailed information on the stunning methods
allowed under the Humane Methods of Slaughter Act.
You're quite welcome. And if you need more information on the Act and
these stunning methods, please go to: www.fsis.usda.gov.
Thanks, Joan, and thanks to all of you out there listening. Join
us next time when we'll discuss humane handling under ritual slaughter.
Well, that's all for this episode. We'd like your feedback on our podcast. Or if you
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firstname.lastname@example.org. To learn more about food safety, try our web site at
www.fsis.usda.gov. Thanks for tuning
Last Modified: April 15, 2009