Agriculture Reference
In-Depth Information
rotatory and other movements of the cerebral hemi-
spheres, increasing the chance of a tissue-deforming
collision or impact between the cortex and the skull.
This in turn causes diffuse depolarisation and synchro-
nised discharge of cortical neurons (Shaw, 2002). In
addition to these changes, penetrative percussive stun-
ners cause direct damage and trauma to the cerebral
hemispheres and brainstem.
The captive bolt pistol is a very useful instrument,
but it cannot be used for slaughter at rates of over
240-250/hour owing to difficulties in reloading. In these
cases, an automatically resetting stunner can be used.
Pneumatic stunners
, where the bolt is activated under
a pressure of 80-120 psi, require somewhat complicated
actions to fire them, and there may be occasions when
air pressure is inadequate. With proper pressure, how-
ever, a high bolt velocity can be achieved.
Non-penetrative concussion stunners
using a mush-
room-shaped head were sometimes used in calves and
lambs. However, EU Council Regulation 1099/2009 has
banned the use of non-penetrative captive bolt devices in
ruminants above 10 kg bodyweight. Properly used, this
method is capable of producing immediate insensibility.
Much depends on the operative as to whether or not
blood splashing results, especially in the case of lambs. If
the animals are handled properly and the interval
between stunning and bleeding is short, blood splashing
in muscle will be minimal.
If the first blow using a non-penetrative concussive
stunner fails to produce an effective stun, subsequent
shots are unlikely to be effective due to the swelling of
the skin and subcutaneous tissue caused by the first shot.
An alternative backup system, such as penetrative per-
cussion or electrical stunning, should therefore always
be immediately available for use.
(a)
(b)
(c)
(d)
(e)
Figure 7.2
Points of application for concussive stunning:
(a) adult cattle; (b) calves; (c) horned sheep; (d) pigs; (e) horned
goats (by courtesy of the Universities Federation for Animal
Welfare).
for
horned sheep and goats
, the muzzle is placed behind
the ridge which runs between the horns, the direction of
aim being the same.
For
bacon weight pigs
, the stunner is placed about
2.5 cm above the level of the eyes and fired upwards into
the cranial cavity. In older animals, captive bolt stun-
ning is less reliable owing to the massive nature of the
skulls and the large frontal sinuses of older pigs. The
muzzle should be placed about 5 cm above the level of
the eyes to the side of the ridge which is in the mid-line
of the skull, and at right angles to the frontal surface
(Fig. 7.2).
The
contact-firing types
of
captive bolt stunner
are
much more satisfactory than the trigger-operated ones,
only a light tap on the animal's head being necessary to
fire them. With cattle restrained in a stunning box, they
are easier to operate than trigger-operated pistols.
However, if they are dropped on the floor or struck
against the stunning box wall, the whole gun can become
a dangerous missile (Fig. 7.3).
Head sites for percussive stunning
With both types of percussive stunners, care must be
taken to hold the instrument reasonably firmly against
the animal's head at the proper point and direction. In
adult cattle
, the correct point is in the middle of the
forehead where two lines taken from the medial can-
thus of each eye to the base of the opposite horn or
horn prominence cross. The stunner is placed at right
angles to the forehead and after discharge is lifted away
from the falling animal. In
calves
, the pistol should be
placed slightly lower on the head than for adult cattle,
while for
bulls
and
old cows
, the muzzle is placed 1.5 cm
to the side of the ridge running down the centre of the
forehead. Cattle should never be stunned in the poll
position.
In
hornless sheep and goats
, the stunner is placed on
the top of the head and aimed towards the gullet, while
