Agriculture Reference
In-Depth Information
and the potential for infection of operatives. In addition,
the complete removal of a damaged spinal cord is ren-
dered impossible. Consequently, as a result of European
Commission Decision 2000/418, pithing is no longer
permitted for animals slaughtered for human consump-
tion within the EU.
There is some evidence that bacteria can be introduced
into the carcase on the pithing cane and subsequently dis-
persed throughout the carcase before the heart stops
beating. It is therefore imperative that if pithing is carried
out, the cane is sterilised between use on each animal.
Bleeding
Bleeding following stunning must always be carried out
without delay since even when stun-to-kill methods are
deployed, they may not always be effective.
The circulating blood volume in animals is estimated
to be 8% of body weight. Specific volumes for each spe-
cies are given in the following text. Approximately
40-60% of the total blood is lost at bleeding.
Figure 7.9
Cattle bleeding over a blood collection channel
(Reproduced with permission from Sarah Jackson).
their division into
internal and external maxillary veins
;
this permits easier skinning of heads and also reduces
the quantity of blood in the lingual artery. The vertical
head-down position of the suspended carcase otherwise
causes blood to be retained in the head.
The ordinary bleeding knife severs blood vessels more
rapidly if the blade is held at right angles to the direction
of the vessels and longitudinal axis of the body.
Whichever method is employed, bleeding should con-
tinue for 6 minutes. The average
yield of blood
obtained
in
cattle
slaughter is 13.6 kg.
Cows
yield more blood than
bulls or bullocks of the same weight, in some cases up to
22.6 kg in old cows. About 57.3% of the blood is yielded
in the first 30 seconds after sticking, 76.6% after 60 sec-
onds and 90% after 120 seconds.
In
calves
, the incision was at one time at the side of the
neck with the severing of the jugular vein. The purpose
of this was to produce slow bleeding after the carcase was
hung up prior to dressing, for slow bleeding ensure the
desirable white colour of veal. Calves are now bled rap-
idly at the level of the first rib, and yield 2.7 kg of blood.
Cattle
There are two main methods of bleeding
cattle
:
1
Bilateral severance of the carotid arteries and jugular
veins
by an incision across the throat region caudal to
the larynx as in ritual slaughter
2
Incision in the jugular furrow at the base of the neck,
the knife being directed towards the entrance of the
chest to sever the
brachiocephalic trunk
and
anterior
vena cava
Care must be taken not to pass the knife too far towards
the chest for, if the pleura is punctured, blood may be aspi-
rated into the thoracic cavity and adhere to the parietal
pleura, particularly along the posterior edges of the ribs.
This contamination is known as
back bleeding or over
sticking
and, may necessitate stripping of the pleura. In
cattle, the blood cannot infiltrate between the pleura and
contiguous chest wall; this may occasionally occur in pigs
but over a small area immediately posterior to the first rib.
Current abattoir practice is to stun cattle and then
hoist them, by the shackling of a hind leg, over a bleeding
gully. The advantage of a bleeding rail is that it permits
centralised collection of blood and also accelerates the
throughput of animals, allowing them to be stunned and
removed in quick succession through the same stunning
pen. Observations have shown that bleeding was 40%
more effective in cattle bled on the rail than in those bled
in a horizontal position (Fig. 7.9).
If unilateral sticking at the base of the neck is
performed, it is of value to make other small bilateral
incisions at the angle of the jaw, severing the jugulars at
Sheep
In the slaughter of sheep, bleeding is usually carried out
by an incision in the jugular furrows close to the head,
severing both
carotid arteries
and
jugular veins
. However,
thoracic inlet bleeding
is superior as it reduces the risk of
contamination of the cut surfaces with ruminal content
from the severed oesophagus which frequently occurs
with the former method. However, accidental cutting of
the oesophagus may still occur with this method. At one
time, when cradle dressing was carried out, it was cus-
tomary to jerk the head back sharply in order to rupture
the spinal cord where it enters the skull, the purpose
being, as in the pithing of cattle, to minimise reflex
