Agriculture Reference
In-Depth Information
Figure 7.4
Captive bolt pistol, taken to pieces for daily cleaning.
All forms of mechanical stunning devices should be
fitted with safety levers to minimise the chances of
accidents.
A backup stunner should always be on hand in case
of emergency.
Bolt velocity check
A device is now available for checking the bolt velocity of
all Cash penetrative stunners. The stunner is placed
upright in the device and fired, stunning performance of
the various cartridges being recorded as FAST, OK or
SLOW by means of indicator lights on a separate
recorder. Accurate monitoring of stunner performance
means more effective stunning, fewer second shots,
greater operator efficiency and safety, and a high stand-
ard of animal welfare.
Figure 7.3
Contact firing penetrative concussive stunner for cattle.
A defect of percussive stunning and the use of the free
bullet is noise. Most of the really serious defects, how-
ever, arise from misuse or from instruments in poor state
of repair, as is the case with all forms of stunning. The
Official Veterinarian must be satisfied that the instru-
ments used for stunning, and for restraint, are in a good
state of repair.
If equipment is to function correctly, the importance
of
regular maintenance
cannot be overemphasised. The
velocity of the bolt may be significantly reduced by a
build-up of carbon or corrosion on the piston, which
drives the bolt forward, or by excessive wear in any of the
moving parts. While some manufacturers recommend
cleaning every 70 shots,
daily dismantling and thorough
cleaning must be carried out
. A record of cleaning and
maintenance should be kept by the operator and audited
by the Official Veterinarian as part of a regular check of
the equipment (Fig. 7.4).
A common indication that a stunner requires cleaning
is the tip of the bolt protruding from the muzzle more than
the usual distance when the bolt returns to the barrel.
Neural tissue embolism in cattle
With the realisation that Transmissible Spongiform
Encephalopathies (TSEs) were zoonotic, considerable
interest focused on the possibility that percussive stun-
ning could result in emboli of brain tissue entering edi-
ble tissues. Garland, Bauer and Bailey (1996) in the
United States reported the condition in 2.5-5% of cattle
stunned by a pneumatic-actuated penetrative captive
bolt pistol, the diaphragmatic lobe of the lung being the
area most commonly affected. Pneumatic stunners,
which inject compressed air through the captive bolt
into the cranium, disintegrate the brain and are most
likely to result in emboli. Pneumatic powered stunners
that do not inject air present a reduced risk but greater
than that of cartridge-driven stunners. However, pene-
trating captive bolt stunning has been demonstrated to
result in central nervous system (CNS) embolism in jug-
ular blood in a large percentage of both cattle and sheep.
In non-penetrative captive bolt stunning, CNS material
