Humane-Slaughter-Guidelines

D1.7 Conditions That Cause Welfare Problems
1. Failure to provide nonslip flooring—One of the
most common problems in stun boxes is slippery
floors. 49 When animals are continuously slipping,
they cannot stand still for stunning. Designs for
nonslip floors can be found in the section of the
document that describes unloading. Metal grating
or rubber mats work well to prevent slipping in
stun boxes.
2. Overloading equipment beyond its design capacity—Two
of the most common mistakes are overloading
a single conveyor restrainer and overloading
of undersized CO 2
stunners:
a. Overloading a single conveyor restrainer. If the
goal is to have 1,000 pig carcasses/h enter the
coolerr, the restrainer will need to accommodate
1,200 live pigs/h. When pigs are forced to move
faster than 850 pigs/h in a single line, they are
moving faster than their normal walking speed.
Most large plants in which 1,000 pig carcasses/h
enter the cooler have two conveyor restrainers
with two single-file chutes and two crowd pens.
A single center-track restrainer will work well
to process 390 cattle/h if it is free of the distractions
discussed previously. At 390 cattle/h,
the cattle are still moving at a normal walking
speed. For both electric prod use and vocalization,
there are few differences among different
line speeds when equipment is designed and operated
correctly. 56
b. Overloading of undersized CO 2
stunners. Carbon
dioxide stunning equipment is available in
many sizes. One of the most common problems
is when a plant’s expansion causes it to outgrow
its CO 2
stunner. Unless the CO 2
stunner is replaced
with another machine having a higher
capacity, the the following welfare problems are
likely to emerge:
i. Overloading gondolas by using electric prods
to force excess pigs to load. Pigs should have
sufficient room to stand in the gondola without
being on top of each other.
ii. Reducing gas exposure time in an attempt to
increase the number of pigs the machine can
handle per hour. This will result in conscious
pigs emerging from the stunner.
c. Overloading single-animal stun boxes and restrainers.
Single-animal stun boxes or restraint
boxes have a maximum speed of approximately
100 animals/h. Boxes designed to hold single
animals result in slower line speeds than than
conveyer systems, because they use a start-stop
process to put each animal in the box and then
remove it. The signs of an overloadedbox are:
i. Slamming the rear gate on animals,
ii. Increased electric prod use,
iii. More than one animal in the box for stunning,
and
iv. An increase in rough handling.
For all species, when the line speed exceeds 100
animals/h, the use of a conveyor system that handles
a continuous stream of animals or two or more singleanimal
boxes is recommended.
3. Funnel-shaped crowd pens. Movement of pigs will
be impeded in a funnel-shaped crowd pen; therefore,
a crowd pen that leads to a single-file chute
should have an abrupt entrance. 32 The entrance to
the single-file chute should be just wide enough to
allow one pig to enter. If it is too wide, two pigs
may become stuck beside each other entering the
chute. Designs for appropriate crowd pens for
cattle, sheep, and pigs may be found in publications
by Grandin, 5,28,69 the Horse Welfare Association
of Canada, 9 and the American Sheep Industry
Association. 79
4. Stun boxes and single-file chutes that are too wide.
The appropriate width for stun boxes and chutes
tends to be overestimated. Stun boxes and chutes
that are too wide result in animals turning around
and becoming caught beside each other. The appropriate
width is 30 inches (76 cm) for cattle, 18
inches (46 cm) for market-weight pigs, 32 inches
(81 cm) for horses, 16 inches (40 cm) for sheep,
and 27 inches (70 cm) for deer. Chute width may
need to be adjusted for exceptionally large or small
animals.
5. Vertical overhead gate clearance is too low. Animals
will often refuse to walk under a vertical slide gate
or other apparatus that allows for scant clearance
or touches their back. Raising the opening height
6 inches (16 cm) will usually fix this problem. On
center-track restrainers, the solid hold-down cover
may need to be raised to prevent bumping of the
animal’s shoulder when it is entering.
6. Single-file chute is too short. The single-file chute
has to be long enough that a sufficient number of
animals can be held within it to allow time to refill
the crowd pen (Table 1). The recommended
lengths should be used for systems in which animals
are handled in a continuous flow to the processing
line. In systems where animals are handled
rapidly in separate batches, shorter chutes (races)
can be used.
7. Animals allowed to stand in a stun box too long.
Animals should be stunned immediately after they
enter the stun box or restrainer. Holding an animal
alone in a stun box can cause isolation stress.
D.2 Handling Procedures at Slaughter Plants for Poultry
D2.1 Step 1—Electric Stunning, CAS, and LAPS:
Arrival and Lairage
Poultry arrive at the plant and are weighed on a
truck scale while they are still on the vehicle. After
weighing, the poultry truck is parked in the lairage
shed with the birds still in the travel containers. The
sheds are equipped with fans and misters to keep the
Table 1—Recommended single-file chute lengths for cattle.
Species Line speed Minimum length Maximum length
Cattle Under 25/h 20 ft (6 m) 75 ft (23 m)
Cattle 25–100/h 40 ft (12 m) 75 ft (23 m)
Cattle 200–390/h 80 ft (25 m) 200 ft (23 m)
Pigs and sheep Under 100/h 10 ft (3 m) 25 ft (7.6 m)
Pigs Over 100/h 25 ft (7.6 m) 50 ft (15 m)
Some systems with lengths longer than those recommended
here may work well.
AVMA Guidelines for the Humane Slaughter of Animals: 2016 Edition 19