Agriculture Reference
In-Depth Information
attracted. Food containers must never be stored outside
even when the intention is to wash them before reuse.
They provide attraction and harbourage for vermin and
pests and could inadvertently be brought into use before
effective sanitation had occurred.
ing the animals may result in release of dust which
adheres to the hot carcase while the fleece is being
removed.
In all cases, the welfare aspects of the husbandry
practices which have resulted in the dirty animals should
be borne in mind, and farm inspections by the appropriate
agency instituted where necessary
.
In New Zealand, it has been common practice for
many years to wash lambs through plunge dips prior to
slaughter. A study of this practice by Biss and Hathaway
(1996) indicated that, although the carcases of washed
lambs showed evidence of less visible contamination
than those of unwashed lambs, washing had a detrimen-
tal effect on the microbiological load as measured by
E.
coli
and aerobic plate counts. The same study showed
that the levels of visible and microbiological contamina-
tion were lower on carcases derived from clipped when
compared with 'woolly' lambs. In the United Kingdom,
many slaughter establishments routinely clip the incision
lines and 'crutch' of dirty lambs in the lairage and charge
the producer for the service.
Washing heavily cladded cattle in the lairage is futile
from a hygiene perspective, and may be highly detri-
mental to animal welfare. It is impossible to wash the
legs, hooves and ventral aspect of cattle effectively.
Commercial application of an apparatus to wash bovine
carcases post-bleeding and pre-evisceration has been tri-
alled. The treatment involved spraying the carcase for 10
seconds with a 1.5% solution of sodium hydroxide at a
temperature of 65°C followed by a rinse with a solution
of sodium hypochlorite containing 1 ppm free chlorine.
The treatment had little effect on the total number of
aerobic bacteria or enterobacteria on the surface of the
dressed carcase but resulted in a significant reduction in
the prevalence of
E. coli
O157:H7.
A process for
chemically de-hairing
cattle between
stunning and sticking has been patented in the United
States. It involves repeated applications of 10% sodium
sulphide solution and rinses with 3% hydrogen peroxide
within a closed cabinet and results in the complete
removal of dirt, faeces and hair. However, a study of the
process by Schnell
et al.
(1995) demonstrated that,
although there was less visible contamination on the
treated carcases than on conventionally slaughtered con-
trols, total bacterial counts, measured as aerobic plate
counts and total coliform counts, showed no decrease in
the overall bacterial load. A further study of this process,
Nou
et al.
(2003), however concluded that there may be
value in the process.
Bosilevac
et al.
(2004) applied a detergent surfactant,
cetylpyridinium chloride (CPC 1% w/v), to the hides of
cattle in the lairage immediately before stunning in order
to determine its effectiveness as an intervention for car-
case contamination from the hide. The treatment was
Chemical contamination
Cleaning chemicals may contaminate the meat if they
have not been used in accordance with the manufac-
tures' instructions. Only chemicals suitable for use in the
food industry should be used for sanitising the slaugh-
terhouse. Most cleaning agents need to be rinsed off the
structures correctly. It is not uncommon to find a residue
of chemical on sanitised stands and equipment after they
have dried. Some sanitising agents are designed to be left
on surfaces and do evaporate to leave a residue-free sur-
face. All rail grease and lubricating oils should be food
grade. Chemicals used in the food factory cannot be
stored in rooms where food is handled. Ideally they
should be stored in a specifically designated store away
not only from food but any materials that might come
into contact with food, for example, wrapping or packag-
ing materials. The operator must be able to provide evi-
dence of the suitability of the chemicals used and
information on their correct use.
The hazard of intrinsic chemical residues in the meat
is dealt with in Chapter 13.
Methods of reducing contamination
Dealing with the dirty animal
It is almost inevitable that, despite all efforts to prevent it,
dirty animals will be presented for slaughter, especially
in the winter months in the British Isles. The operator
must have a procedure for screening and subsequently
handing and hygienically dressing the varying degrees
and nature of dirty animal presented taking account of
animal disease control restrictions and animal welfare
considerations.
The first option to be considered should always be to
reject without slaughtering, but disease restrictions or
animal welfare considerations may make this impossible.
It is widely agreed that in most cases it is easier to hygien-
ically dress dirty, dry cattle and sheep than dirty, wet
ones. Slaughter should then be delayed until the animals
are dry by resting them in straw yards or, in the case of
sheep or lambs, on expanded metal floors. A technique
recommended by one experienced veterinarian to assess
when dirty wet lambs are sufficiently dry to allow
hygienic dressing is that lambs should be detained until
their underside can be rubbed without dirtying the hand.
It should be recognised, however, that in warm climates,
and where lambs have been fattened on root crops, dry-
