Hygiene of Slaughter – Sheep - Hygiene of Abattoir Operations

Hygiene of Abattoir Operations

5.3 Hygiene of Slaughter – Sheep

The general ﬂow of operations during sheep slaughter and dressing is illustrated in Fig. 5.2.

General Hygiene Requirements

The same principles and practices of hygiene during slaughter and dressing described for cattle are also applicable to sheep, so these will not be repeated in this chapter. However, there are also some speciﬁcs related to sheep/goat slaughter and dressing, and these are mentioned below.

Unloading and lairage Ante-mortem inspection Purchase and transport

Stunning Shackling Opening of fleece at neck

Sticking and bleeding

Brisket sawing

Head removal

Eviscerating Carcass splitting

Trimming

Carcass weighing, grading and health marking Washing

Chilling

Inverted dressing

Suspension of carcass from forequarters Opening of fleece on body

Fleece removal, anus to shoulder

Opening of fleece on body Fleece removal, shoulder to anus Head removal

Conventional dressing

Inversion of carcass

Fig. 5.2. Flow of sheep slaughter and dressing operations.

Hygiene of abattoir operations

Stunning

The electrical stunning method is most commonly used for stunning sheep.

Head-only stunning results in the animal losing consciousness, but the heart remains beating. Head-to-chest stunning stops the animal’s heart, resulting in death. Either of these stunning methods are acceptable. Penetrative captive-bolt stunning may also be used, but this carries the same risks as it does for cattle: dissemination of CNS embolism via the blood system to edible tissues, as well as cross-contamination from leakages from the stun hole. These are unacceptable from the public health perspective, although BSE has not yet been found in sheep – but has been in goats.

Sticking/bleeding

The two-knife system must be used for the sticking procedure, with sterile knives being used. Sheep with longer wool may present a greater risk of meat contamination, so shearing of sheep before slaughter – preferably on- farm – is beneﬁcial.

Skinning

There are two basic methods for skinning (de-pelting) sheep and other small ruminants: inverted and traditional.

Inverted de-pelting commences at the cleaner parts of the animal, i.e.

head and forequarters. Initial cuts are made on the front legs, along the neck and towards the brisket, and the ﬁrst cut is then expanded. Punching of the ﬂeece to initially separate it from the underlying muscle tissue occurs, which can potentially produce contamination of the meat if the operator has dirty hands. Operators should avoid swapping ‘dirty’

(holding ﬂeece) and ‘clean’ (holding knife or punching) hands during the dressing procedures for small ruminants, in the same manner as for large ruminants. Use of crocodile clips can help stop in-rolling of the ﬂeece.

After these initial stages, skinning is completed by using various types of mechanical pelt-pullers. The inverted de-pelting system is considered to be more hygienic and to result in lower microbial loads on carcasses.

In contrast, the traditional de-pelting procedure commences the skinning procedure from the more contaminated rear end of the animal.

Animals are usually shackled to the rail by their rear legs, initial cuts made at the rear legs, as well as between the legs, and the pelt is pulled downwards. This traditional de-pelting method is perceived to produce a higher risk of cross-contamination of the carcass, as the action involves pulling the dirty ﬂeece downwards from the dirtiest part of the animal towards the cleanest parts. Modern sheep abattoirs most frequently use the inverted dressing system. However, the traditional system is still predominant in smaller abattoirs with low throughput, on farms and when sheep are slaughtered by hunters.

During sheep de-pelting, it is difficult to achieve the low contamination rates capable of being achieved during cattle de-hiding, as the animal is smaller, the fleece is longer and there is a much greater chance of fleece in- rolling and contacting the carcass. Therefore, overall, de-skinning is a

‘dirtier’ procedure in small ruminants than in larger ones.

De-pelting can be aided by injestion of compressed gas (air) under the skin using an inserted needle, which separates the skin from the carcass before skinning begins. This can make de-pelting easier, with less handling, and therefore more hygienic. However, there is a potential for gas de- pelting mediating cross-contamination, unless the air is ﬁltered and the needle sterilized/changed between animals.

Heads of sheep may or may not be destined for human consumption.

If the head is destined for human consumption, it is skinned; if not, it is left skin-on and removed later, subject to proper post-mortem inspection.

Evisceration

The oesophagus is released from the trachea and tied, in a manner similar to that used for cattle.

The anus is released, and the rectum is tied or bagged. Evisceration commences by cutting the abdominal walls, taking care not to puncture the guts. The whole abdominal cavity is emptied; the organs are removed in one piece.

The sternum and the thoracic cavity are opened so that the lungs, heart and, usually, liver linked with diaphragm, can be removed.

The red offal is separated from the green offal; the latter is removed and handled in a separate room outside the slaughterhall. With sheep, only the ileum need be removed as SRM. The different parts of the pluck must be separated, washed and trimmed.

Carcass washing

Lambs are normally washed between the completion of de-pelting and the beginning of evisceration. Any visible contamination on the carcass after dressing must be trimmed and not washed. However, a ﬁnal wash is necessary to ensure that any remains of wool or ﬁne hair is removed from the carcass.

Chilling

Carcasses must be chilled to ⱕ7°C, and edible offal to ⱕ3°C, adhering to the same hygienic principles as described for cattle.

BSE control measures

Speciﬁed risk material (SRM) must be removed during the dressing of an animal and disposed off appropriately; for details see Chapter 6.3.

Hygiene of Slaughter – Sheep

Hygiene of Abattoir Operations

5.3 Hygiene of Slaughter – Sheep

General Hygiene Requirements

Further Reading