Meat hygiene practice - Gracey's Meat Hygiene - page 157

Transport of cattle or sheep to the slaughterhouse may
increase the number of salmonella organisms shed into
livestock waste and the percentage of animals shedding,
but this is not the case for all food poisoning bacteria,
for example, E. coli O157. The longer the animals
remain in the lairage, the greater the potential for cross-
contamination. This is particularly the case for pigs if
pens are not properly cleaned between batches and if
they are held overnight.

Table 8.1 Prevalence of zoonotic agents on cattle hides
(various studies)

Zoonotic agent Prevalence on cattle hides (%)

E. coli O157 1.0-27.8

Salmonella 5.5-10

Campylobacter 0-33

In Finland, the problem of excessively dirty cattle
being presented for slaughter was greatly reduced by the
application of a series of rules agreed by meat inspection
veterinarians, farmers, the meat industry, the leather
industry and the state veterinary department. Under this
agreement, excessively dirty animals are detained to be
slaughtered separately after the clean animals, the extra
cost incurred being billed to the owners involved. This
has resulted in a decrease in the numbers of excessively
dirty cattle by 85% (Ridell and Korkeala, 1993).
In the United Kingdom, a clean livestock policy was
introduced during 1997. It was very successful in ensur-
ing that cleaner cattle and sheep were slaughtered for
human consumption. Until the advent of the revised
European food hygiene legislation in 2006, those
considered by the official veterinarian to be in an unac-
ceptable state at ante-mortem inspection had to be
cleaned up in the lairage before being re-presented
for ante-mortem inspection. Animals unable to be
adequately or effectively cleaned for welfare or health
and safety reasons were consigned to by-product or, in
rare cases, allowed to return home. Since 2006 in
Europe, the slaughterhouse operator has assumed the
responsibility for determining the condition of cleanli-
ness that their production process can effectively deal
with. These procedures must be built into the food
safety management controls to be monitored and
verified by their own system and meeting the process
hygiene criteria set in European microbiological crite-
ria regulation. The slaughterhouse operator's system is
subject to the independent verification of the official
veterinarian and inspection team.

Stunning and sticking
Work carried out by Daly et al. (2002) and Buncic et al.
(2002) suggests that bacterial contamination introduced
into the carcase during penetrative captive bolt stunning
may become widely dispersed across the slaughter line
environment and within carcases, their surfaces and edi-
ble offals. During the act of sticking, bacteria can enter
the jugular vein or anterior vena cava and travel in the
bloodstream to the muscles, lungs and bone marrow.
Many have questioned whether bacterial contamination
by this route is of great importance (Troeger, 1994).
However, since it has been demonstrated that marker
bacteria can enter the circulation by this route (Daly et
al. , 2002), it is imperative that hygienic two-knife tech-
nique, initial spear cut through the skin followed by
severing of the blood vessels using a second, is a routine
part of GHP.

Physical contact with structures
The design of the line must allow for a full range of sizes
of stock so that legs do not touch stands or supports and
necks or heads do not drag along the floor, walkways or
tables. A common weak point occurs at the point on the
line where the bovine gastrointestinal tract is dropped
on to the gut table, chute or conveyor. Gross cleaning,
with squeegee and shovel, etc., must be ongoing through-
out the working day to prevent the build-up of blood and
debris. As part of GMP/GHP, every opportunity must be
taken during breaks in production when the slaughter
floor is free of carcases and offal to rinse down the line.
Care must also be taken to ensure that the position
and height of offal rails is such as to prevent contact with
the floor or structures. Swinging viscera, particularly at
corners, may come into contact with supporting struc-
tures, while poor positioning of the line frequently leads
to operatives dragging viscera across the floor, platforms
or the line structure for hanging.

Gastrointestinal tract
Accidental puncture of the stomach and intestines is a
source of contamination on occasions, as is spillage from
the rectum and oesophagus. It has been estimated that
the mixed bacterial flora of the gastrointestinal tract may
reach 10 10 colony-forming units (cfu) per gram of
contents.
Rupture of the stomach or intestines is more likely
where there is an underlying pathology, for example,
navel abscess in lambs, traumatic reticulitis in cattle and
peritonitis in pigs.

Operatives
All persons working in the slaughter hall are an impor-
tant, and extremely mobile, source of contamination and
means of cross-contamination for the meat. Movement of
all personnel about the plant must be strictly controlled,