LAB 1.1 Stages of slaughter operation
1. Ante-mortem inspection.
Antemortem means before death - so this is the inspection of the live
animal. The inspector will be looking for animals which are crippled
and cannot walk properly. These will be slaughtered separately
because they will not be able to negotiate the raceways in the
abattoir. The inspector will look for animals with signs of a fever or
abnormal behaviour (particularly animals which might have a central
nervous system disease). These will be separated and treated specially.
For example, this is where outbreaks of very serious diseases like hoof
and mouth would first be detected and the panic button activated.
2. Stunning. The
animal must be rendered unconscious before it can be killed by
exsanguination (except where there are religoius exemptions). The
method of stunning varies considerably, although concusssion is the
most widely used method. Hand-operated captive-bolt pistols with
a .22 blank cartridge are common, but pneumatic concusssion systems or
electrical stunning may be used in very large abattoirs.
3. Exsanguination (sticking
or bleeding). While unconscious, a sticking knife is used
to open the thick hide at the base of the animal's neck. A second knife
is used (the first is now dirty) to penetrate the clean tissues under
the hide and to sever the major blood vessels from the heart to the
head. Care is needed because bacteria may be carried into the
animal (veins may have negative pressure) from where the bacteria may
rapidly contaminate the meat deep in the carcass.
4. Skinning (removal of
hide). Most beef hides are used for leather production.
Thus, they are valuable and must not be damaged by cuts as the hide is
removed from the carcass. Cuts are made along the medial
(inside) faces of the limbs and along the animal's belly to facilitate
the removal of whole hides with as little loss as possible. The
apparatus used varies with the size of the abattoir. Large abattoirs
will have a hide puller which pulls off the whole hide (like skinning a
rabbit). Small abattoirs may use an air knife (two
counter-oscillating circular blades) which reduce the risk of cutting
through the hide. At a local level, a skinning knife may be used -
but this will be a lengthy operation.
5. Evisceration (removal of
guts). The viscera are removed from posterior to anterior (from
the rear of the animal to the front), starting in the abdominal cavity
and finsihing in the thoracic cavity. The udder or penis are
first to be removed, togther with any cod fat in the region between the
animal's hindlimbs. This opening then allows removal of the bladder and
uterus (if a female), followed by large and small intestines.
Great care is taken in the removal of the anus and rectum, which are
first closed off with a plastic bag to prevent faecal contamination of
the carcass. Similarly, the oesophagus is tied off at the other end of
the gut to prevent contamination of the throat of the carcass. After
the intestines, the rumen is removed, followed by the liver and
diaphragm. The diaphragm separates abdominal and thoracic cavities and
must be cut away from the rib cage. The muscular part of the diaphragm
remains on the carcass (it is composed of edible red meat). The lungs,
heart and trachea are removed togther - these items are called the
6. Post-mortem inspection.
This is a search for parasites, infected lymph
nodes and signs of disease in the viscera removed from the carcass. Key
components to be inspected are usually spread out on a large tray.
7. Final carcass preparation.
This includes trimming (bruises and tags of inappropriate
tissues remaining on the carcass), washing and weighing. Washing
frequenctly includes a rinse with fluids such as lactic acid which have
Meat is NEVER frozen
straight off the kill floor, but must be cooled as rapidly as possible
to reduce surface bacterial spoilage. The first meat cooler is
around zero degrees centigrade with a high air speed and a high
humidity. It takes all day to cool down a large mass of meat. The
day after slaughter, carcasses are moved to a less severe environment
(high air speed would dry the carcass too much, while a high humidity
would encourage spoilage by surface moulds). Dspite the importance of
reducing meat spoilage, the carcass must not be cooled too rapidly or
else the muscles will shorten (COLD SHORTENING) and the meat will
become very tough. The rule of thumb for beef is not to get below
10 C within 10 hours of slaughter.
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Preparation for slaughter
The optimum amount of rest required by meat animals before they are
depends on the climate, the distance they have travelled, their method
of transport and their general health. In some countries, where animals
are auctioned at stock yards before they are taken to an abattoir, the
rest periods are sometimes inadequate. This creates a commercial
that is difficult to evaluate. On one hand, animals lose weight during
transport and in holding pens, and it is undesirable to use pens and
to prolong a rest period that confers no immediately obvious commercial
advantage. On the other hand, stressed or weary animals sometimes
meat with an unacceptable appearance or water holding capacity, and
may create economic losses later on. Animals lose about 0.2% per hour
their live weight once feeding has ceased, but this is very variable.
beef cattle, losses in 48 hours of fasting may range from less than 1%
to 8%. About half the live weight loss shows up as a loss in carcass
However, improvements may be gained by electrolyte therapy, allowing
free access to drink electrolytes during lairage.
In some situations, a rest period of one day for cattle and two or
days for pigs is considered to be optimum. However, such rest periods
be counter productive if the animals fight among themselves. Animals
not fed in the 24 hour period prior to slaughter.