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CHAPTER 7: Slaughter of livestock


Preparing livestock for slaughter
Restraint devices
Stunning methods
Malpractice in immobilization of livestock
Religious or ritual slaughter (Halal and Kosher)
Bleeding
Determining insensibility at slaughter

The obligation in the conversion of food animals into edible products and useful by-products is to slaughter the animal in a humane manner and to process the carcass in a hygienic and efficient way.

Preparing livestock for slaughter

At the time of slaughter, animals should be healthy and physiologically normal. Slaughter animals should be adequately rested. They should be rested, preferably overnight, particularly if they have travelled for some times over long distances. However, pigs and poultry are usually slaughtered on arrival as time and distances travelled are relatively short and holding in pens is stressful for them. Animals should be watered during holding and can be fed, if required. The holding period allows for injured and victimised animals to be identified and for sick animals to be quarantined.

When ready for slaughter, animals should be driven to the stunning area in a quiet and orderly manner without undue fuss and noise (Fig. 8, 9, 26). Droving can be facilitated using flat canvass straps (Fig. 8), rolled plastic or paper, and in the case of stubborn animals, prodders (Fig. 6) can be used occasionally. Animals should never be beaten nor have their tails twisted. Animals should be led in single file (Fig. 24, 25, 27) into the stunning area where they can be held in appropriate restraining device(s) before stunning.

Restraint devices

It is very important that slaughter animals should be properly restrained before stunning or bleeding. This is to ensure stability of the animal so that the stunning operation can be carried out accurately and properly. Different types of restraints are appropriate for different species:

Cattle

A stunning box is the most common method of restraining cattle (Fig. 25, 44). The size of the box should be just wide enough to prevent the animal from turning around, and so be difficult to stun. The floor of the box should be non-slip. A simple neck crush used by farmers to restrain cattle for weighing is suitable for small-scale operations (Fig. 45). Restraining tame cattle outside the stunning box by securing the head in a halter and then pulling the rope through a metal ring in a concrete floor is effective. It is recommended that the operator should be positioned behind protective steel bars (Fig. 46).

Fig. 44: Stunning box for cattle

Fig. 45: Simple, effective race and neck crush for cattle restraint

Fig. 46: Small-scale operation position of the pre-stunning operator behind protective steel bars

Sheep/goats

A properly constructed metal stunning box is appropriate (Fig. 47). However, they can be restrained manually quite satisfactorily.

Fig. 47: Sheep/goat stunning box

Pigs

A stunning box is suitable for pigs (Fig. 48). Putting a few pigs in a small room is suitable but only for electrical stunning (Fig. 57, 58). On no account should pigs be restrained manually.

Poultry

Chickens are shackled by their legs onto a conveyor line (Fig. 49). This must be done gently to avoid injury and stress. In a small slaughterhouse, birds can be placed headfirst in cones (Fig. 50).

Ostriches

These are temperamental animals, and because they will kick, they must be securely restrained. This can be done by leading them into a padded V-shaped pen, with the head facing the apex of the pen. Also the feet can be clamped immediately after electrical stunning has begun (Fig. 59).

Animals should never be left standing for a prolonged period in a restraint device and must be stunned immediately after being secured. The operator must be adequately trained and supervised. In some countries, people who handle and stun animals have to be trained and licensed.

Fig. 48: Stunning box/restrainer for pigs

Fig. 49: Poultry shackled on conveyor by legs prior to electric stun

Fig. 50: Stun/bleed cones for small-scale poultry slaughter

Stunning methods


Percussion stunning
Electrical stunning
Carbon dioxide gas stunning (Fig. 64, 65)

It is desirable to render an animal unconscious before it is slaughtered in order to eliminate pain, discomfort and stress from the procedure. Most developed and many developing countries have legislation that requires pre-slaughter stunning, with the exception of authorised ritual slaughter like Kosher or Halal. In some circumstances, traditional slaughter may be exempt from pre-slaughter stunning. Whatever the stunning method, the animal should be rendered unconscious for long enough so that bleeding results in enough loss of blood to cause death from lack of oxygen to the brain (cerebral anoxia). In other words, death should occur before the animal would have regained consciousness after stunning, had bleeding not taken place. There are three main technologies used to effect stunning-Percussion, Electrical and Gas. Only the first two are commonly used in developing countries.

Percussion stunning

This method produces a physical shock to the brain (Fig. 51).

Captive bolt

This method works on the principle of a gun and fires a blank cartridge and it propels a short bolt (metal rod) from the barrel. The bolt penetrates the skull bone and produces concussion by damaging the brain or increasing intracranial pressure, causing bruising of the brain (Fig. 52). The captive bolt is perhaps the most versatile stunning instrument as it is suitable for use on cattle, pigs, sheep and goats as well as horses and camels, and can be used anywhere in the world. (Although electrical stunning is preferable to captive bolt pistols for stunning pigs and sheep.) There are several different manufacturers of captive bolt pistols, and after the initial expense, running costs are minimal. Users must ensure sufficient supply of cartridges, which may be different in caliber for stunning guns from the different manufacturers. These features make the captive bolt the stunning instrument of choice, particularly in developing countries.

There are two variations of the gun. One has a handle and trigger. The other comprises hand-held barrel, which is tapped against the skull, which sets of the cartridge explosion (Fig. 52, 53).

Another type of bolt has a flat, mushroom end (Fig. 55). Unconsciousness is achieved through percussion by strong blow to the skull. The brain is not penetrated, and as the animal is not killed, it is a method that is acceptable in many countries for Halal slaughter. When in use, the captive bolt is positioned on the correct spot on the animal’s head (Fig. 51, 53, 54). Poor maintenance is a major cause of poor stunning and the guns must be cleaned and serviced regularly, according to the manufacturer’s instructions.

Fig. 51: Correct positioning of stunning gun for different species (horse, cattle, goat, sheep and pig)

Fig. 52: Use of Captive Bolt Pistol (CBP)

A. Bottom part removed from main part of CBP for loading the cartridge
B. CBP in firing position (firing pin to be released through trigger)
C. BP with expelled bolt after firing (rubber rings stop expulsion and partially withdraw bolt)
Fig. 53: Hand-held barrel captive bolt gun

Fig. 54: Wrong position of the captive bolt pistol (see also Fig. 51)

Fig. 55: Mushroom bolt stun gun

For effective stunning, it is important that the operator is well trained in its use of the stunning gun. If the operator becomes fatigued, accuracy of stunning is reduced, so in large plants, rotation of two stunners is recommended. Stunning of bigger pigs may require a stronger cartridge, as the sinus cavities of the skull are larger. Large bulls have a bony ridge in the forehead and penetration may be more difficult, requiring off-centre aim. A captive bolt gun is not suitable for stunning ostriches. Their brain is small and lobulated, and the bolt does not produce proper concussion.

Gunshot

In circumstances where animals are too fractious to be handled in the normal way, such as when they cannot be loaded on the farm or led into the stunning restraint, gunshot with a free, soft-nosed bullet is effective. A 22-calibre bullet is sufficient for most animals. Shooting with a free bullet can be dangerous to operators. If the animal is to be slaughtered on a farm, it should be accurately shot while standing or lying on soft ground to prevent the bullet from ricocheting.

Electrical stunning

This method of stunning is well suited for pigs, sheep or goats, poultry and ostriches. (Use in cattle or other large species is in development, but if not properly applied it may result in excessive haemorrhage in the muscles or spinal fractures.) Electrical stunning induces electroplectic shock or epileptic state in the brain. This state should last for long enough for bleeding to be carried out so that the animal dies from cerebral anoxia. A low voltage alternating electric current is applied by means of two electrodes, which are placed on either side of the brain using tongs. Since the brain of animals is small, the electrodes should be accurately and firmly placed high up on the sides of the head in sheep, goats, pigs and ostriches (Figs. 56, 57, 58, 59).

Fig. 56: Tongs for electrical stunning of sheep or goats

Another way is to place one electrode under the jaw and the other on the side of the neck behind the ears. This type of head-only stunning is reversible and the animal will regain consciousness. For this reason, stunned animals should be bled immediately after stunning (Fig. 77).

Irreversible stunning causes cardiac arrest. Here a third electrode is placed elsewhere on the body. Electrodes are applied in the form of tongs. They should never be placed on sensitive areas such as the eye, inside the ear nor rectum.

Fig. 57: Tongs for electrical stunning of pigs

Fig. 58: Tongs for electrical stunning of pigs

Fig. 59: Tongs for electrical stunning of ostriches

Ostriches should be stunned only electrically. The tongs are placed either at the sides of the head below and behind the eye or above and below the head (Fig. 59). Poultry can be stunned electrically using a manually operated device (Fig. 60) or using an automatic water bath (Fig. 61). Here birds are dragged through a trough of water that is charged with a low voltage current.

Fig. 60: Manually operated electrical stunning box for small-scale poultry slaughter

Fig. 61: Water bath for automatic electrical stunning of poultry

The strength of the current is a combination of amperage and voltage appropriate for the species. The equipment should be fitted with a meter to measure the correct current. Approximate current/time guides for different species are as follows:

TABLE 5. Recommended current and time characteristics for electrical stunning

Species

M/Amps

Amps

Volts

Time (sec.)

Pig (bacon/porker)

min. 125

min. 1.25

max. 125

max. 10 (until EPS*)

Sheep/goat

100-125

1.0-1.25

75-125

max. 10 (until EPS*)

Poultry3

1.5-2 kg broiler

200

2.0

50-70

5

turkey

200

2.0

90

10

Ostrich

150-200

1.5-2.0

90

10-15

* EPS is electroplectic shock.

3 An alternative way of electrical stunning of poultry is the utilization of high voltage (300-500 Volts), which causes immediate cardiac arrest. It is claimed that through this method possible insufficient stunning, which may occur in some cases when using the low-voltage stunning, is avoided.

For sheep, goats, pigs and ostriches, during this period the limbs extend the back and head arch and the eyes close. After some 10 or more seconds, muscles gradually relax followed by paddling movements. The electrodes should be removed at this stage as stunning is complete (Fig. 58).

The electrodes should be in good repair and not corroded. They should be cleaned daily. The operator should be competent to ensure correct positioning and good contact of the electrodes. Passage of electric current through the brain is facilitated by cutting the hair over the site or wetting the electrodes. If the whole face or body is wet, the current may short-circuit the brain.

Failure of the operator to apply the apparatus to the correct spot on the head may not produce unconsciousness, resulting in a condition known as missed shock or “the Nightmare State of Leduc”. The animal becomes paralysed and unable to vocalise but remains fully conscious. The simplest commercially available electrical stunning units must have a transformer or other electric circuits that will deliver the recommended minimum amperage and voltage required inducing insensibility.

Unfortunately in many developing countries, homemade devices for electrical immobilisation are still being used. These may be simple wires attached to the animal or homemade tongs but without transformers to achieve the correct current parameters (Fig. 70). Home made stunners plugged directly into the mains are painful to the animals and very dangerous to the operator, as there may be exposed wires.

Fig. 62: Electric stunning of cattle for large-scale slaughtering. Device is started through remote control once animal has entered stunning box.

Fig. 63: Electric stunning of cattle for large-scale slaughtering. Device is started through remote control once animal has entered stunning box.

Generally, electrical stunning of cattle or other large species may result in excessive haemorrhages or spinal fractures due to large muscle spasms. This will be particularly so if unsophisticated technology is used. New Zealand and some other countries have developed modern methods for electrical stunning of cattle to overcome these problems, in particular for beef exports to some Muslim countries or for installation in slaughterhouses in Muslim countries where this method is acceptable (Fig. 62, 63). The New Zealand technique is ‘the Ranguiru System4 or Wairoa Process5, and is a head-only stun.

4 The Ranguiru system is a modified electrical stun, which is applied to Western-type cattle slaughter, where the animal is stunned through the brain and the heart stop beating. It is not accepted as Halal by Muslims.

5 The Wairoa process is a slaughter technique developed in New Zealand, which involves an electrical head-only stunning. This renders the animal insensitive to pain but able to recover if the slaughter cut is not made. The heart remains beating. The system is humane, safe for workers and generally accepted as Halal by Muslims.

Carbon dioxide gas stunning (Fig. 64, 65)

The use of carbon dioxide (CO2) gas is a relatively new method of stunning suitable for pigs and poultry. However, it is applicable only at large industrial plants, as the sophisticated technical equipment is relatively costly to install. Basically, animals are stunned using various concentrations of CO2 in air. Concentrations of CO2 for the stunning of pigs are at least 80% in air for 45 seconds and poultry of 65% for 15 seconds. The acceptability of this method on welfare grounds has been questioned however. For some genetic types of pigs, it may be satisfactory, and for others may be stressful.

Currently Argon gas is being tested for stunning purposes. It is assumed that Argon gas may have some advantages over CO2, but the costs may be higher.

Malpractice in immobilization of livestock

The aim of rendering slaughter animals unconscious prior to bleeding is in good slaughterhouse practice achieved by using captive bolt pistols, electrical tongs or CO2-gas. For the immobilization of bovines and pigs a blow to the skull with a large-sized hammer used to be a wide-spread method and is still being practised, in particular in developing countries. The method requires only manual force, no maintenance of equipment or spares as cartridges, and is therefore cheap (Fig. 66).

A blow with the hammer is certainly preferable to no pre-stunning, but it requires a skilled operator. Very often additional blows are needed, if the animal was not hit properly. The hammer method is prone to a high failure rate and should be replaced wherever possible by one of the above-mentioned stunning methods. Particular malpractice can be observed in pig slaughter, when a number of pigs are driven into a stunning pen and indiscriminately treated with hammer blows. Because they move around, many animals are not hit efficiently; they need additional blows or arrive fully conscious at bleeding (Fig. 66, 67).

Fig. 64: Schematic view of CO2 stunning of pigs. In a discontinuous process the animals enter the CO2 tunnel (a), are lowered into the pit with high CO2 concentration where they fall unconscious (b), are lifted up again (c) and expelled from the tunnel (d).

Fig. 65: Runway and entrance to a CO2-tunnel

Fig. 66: Pre-stunning of buffalo through blow with a hammer

In many places in the developing world, immobilization of large ruminants (cattle, buffalo) is still carried out through the use of a sharp, pointed knife sometimes called a puntilla or Spanish pike (Fig. 68, 69). The knife is used to sever the spinal cord through the space (Foramen magnum) between the skull and neck position of the backbone. Upon inserting the knife and severing the spinal cord, the animal will collapse. It remains immobilized and the operators have easy access; however, the animals remain conscious until bleeding is complete. This practice should be discontinued, as it is not humane.

An equally inhumane method of immobilization of large animals involves severing the Achilles’ tendons, which lead to the collapse of the animal. This practice can in particular be observed in camel slaughterhouses. In camel slaughtering it can also be observed that the animals are immobilized by bending the joints of the fore- and hind legs through tying thin wires around. This forces the animals into a painful sitting position. They may be kept like this for many hours before they are slaughtered.

Malpractice can also be observed in the use of electricity for stunning purposes. Electrical tongs can certainly be fabricated through local engineering work in developing countries, but it is essential that the electrical parameters required for efficient and humane stunning be achieved. Stunning tongs without transformers, using the voltage of the mains not only cause a great deal of suffering but also produce inferior meat quality (Fig. 70).

Absolutely unacceptable are practices using electrical wires attached to the limbs and necks of the animals and inflicting an electrical shock on the animal through connecting to the mains current. Similarly, devices resembling mains-current operated prodders (Fig. 7) but using high voltage, which are utilised for “stunning” of cattle, are inhumane. Moreover, they spoil the meat and damage the skins.

One tormenting method of immobilizing pigs is practised in some Asian countries. Pigs, when moving them from the farms to the slaughterhouses, are forced into crates made of steel bars. These crates can accommodate one pig but do practically not allow any movements upon arrival at the abattoir; the crates are piled one on top of each other. Pigs are kept waiting inside the crate for hours without water and ventilation. Finally the bleeding without stunning is carried out with the pig still in this position (Fig. 71).

Fig. 67: Group of pigs knocked down by hammer blow and being hoisted for bleeding. Some of the animals not fully unconscious

Fig. 68: Puntilla for immobilization of large livestock

Fig. 69: Puntilla for immobilization of large livestock

Fig. 70: Makeshift electric stunning tongs

Fig. 71: Bleeding of pigs in crates by using a knife with long handle

Religious or ritual slaughter (Halal and Kosher)

Most developed and many developing countries of the world require by law an animal to be rendered unconscious before it is slaughtered. This is in order to ensure that the animal does not suffer pain during slaughter. However, exceptions are made for the Jewish (Kosher) and Muslim (Halal) slaughter of livestock. Here stunning generally is not allowed and the animal is bled directly using a sharp knife to cut the throat and sever the main blood vessels. This results in sudden and massive loss of blood with loss of consciousness and death. However, many authorities consider that religious slaughter can be very unsatisfactory and that the animal may not be rendered unconscious and suffer considerable discomfort and pain in the slaughter process.

A number of factors must be given serious consideration before this type of slaughter is acceptable: -

1. Animals that are slaughtered according to Kosher or Halal requirements should be securely restrained, particularly the head and neck, before cutting the throat. Movement results in a poor cut, bad bleeding, slow loss of consciousness (if at all) and pain. This has serious implications for animal welfare. The knife that is used to cut the throat and the carotid and jugular blood vessels must be razor sharp and without blemishes and damage. This is to ensure a swift, smooth cut across the throat behind the jaw and to ensure immediate and maximum gush of blood. Poor bleeding causes slow loss of consciousness and reduces meat quality.

2. Animals should not be shackled and hoisted before bleeding. This causes them severe discomfort and stress. Hoisting should be done only after the animal has lost consciousness Restraining equipment should be comfortable for the animal.

3. Operator competence is of great importance in order to carry out satisfactory religious slaughter, and the authorities should license all slaughter personnel. A poor technique will result in great suffering and cruelty to the animal. Religious slaughter should be carried out paying attention to detail and ensuring the method, equipment and operators are correct. The slaughter process is slow.

The captive bolt gun is suitable for this stunning when using the mushroom shaped head of the bolt (Fig. 55). The mushroom gun is an improvement on the plain bolt, as this bolt does not penetrate the brain and cause death. This should be more acceptable to the religious authorities, and its use would encourage more humane slaughter amongst Muslims in developing countries, thereby improving animal welfare.

Fortunately, many Muslim authorities accept some forms of pre-slaughter stunning. Many Muslim authorities permit electric stunning of cattle, sheep and poultry, whose meat is destined for Muslim communities, because the animals subjected to this stunning method would recover if no bleeding was carried out. Electric stunning is also the method of choice in meat exporting countries where stunning of slaughter animals is required by law, for export to Muslim countries. Similarly, Muslim minorities in countries with stringent animal welfare regulations are allowed to use Halal slaughter methods, but in combination with electrical stunning.

Any kind of prestunning for livestock to be slaughtered according to the Jewish Kosher method has not yet been accepted.

Bleeding

Bleeding is the part of the slaughter process where the main blood vessels of the neck are severed in order to allow blood to drain from the carcass, resulting in the death of the animal from cerebral anoxia. The bleeding knife should continuously be sharpened. A blunt knife will prolong the incision and the cut ends of the blood vessels will be damaged. This may cause premature clotting and blockage of the vessels, delaying bleeding out and prolonging the onset of unconsciousness and insensitivity. Incisions should be swift and precise. In poultry, sheep, goats and ostriches, the throat is cut behind the jaw (Figs. 72, 73, 74).

Fig. 72: Incision for bleeding of poultry (ducks). Animals are immobilized and unconscious as they passed through the water bath for automatic electrical stunning.

Fig. 73: Incision for bleeding sheep

Fig. 74: Incision for bleeding ostriches

The standard method for the bleeding of cattle is to open the skin at the neck between brisket and jaw through a 30-cm longitudinal cut. Then, for hygienic reasons, a clean knife should be used and inserted at a 45° angle (Fig. 75) in order to sever the jugular and carotid vessels.

In pigs, a longitudinal bleeding stick is made into the chest to sever the deep vessels (Fig. 76).

For all cuts, the jugular and carotid vessels should be completely severed. If all vessels are not cut, bleeding may be incomplete, causing excessive retention of blood in the tissue, which can result in early spoilage of meat.

A minimum of delay is required between stunning and bleeding for two reasons:

a. A prolonged delay in bleeding may result in a level of consciousness being regained particularly where animals have been stunned electrically. For example, poultry stunned electrically may regain consciousness within 1-3 minutes. Generally, bleeding of poultry should commence within 15 seconds of stunning. For other livestock, the interval between stunning and sticking/bleeding should also be kept very short. Periods of less than one minute are desirable (Fig. 77).

b. Delayed bleeding will result in an increase of blood pressure, and blood vessels will rupture, causing muscle haemorrhage. This extra blood in the tissue will cause the meat to decompose more quickly, resulting in waste of meat.

Fig. 75: Incision for bleeding cattle

Fig. 76: Incision for bleeding pigs

Fig. 77: Good arrangement for stunning and immediate bleeding of pigs at medium-sized abattoir

Determining insensibility at slaughter

It is important to be able to determine if an animal has become insensible after stunning, as the bleeding and dressing operations must not begin until complete stunning has been achieved.

When cattle, sheep, goats and pigs are stunned using a captive bolt, the animal should collapse immediately. Regular breathing should cease. There should be no corneal or blink reflex, if the eye is touched. These signs of insensibility should be looked for before bleeding commences, usually when the carcass is hanging on the bleeding rail.

In electrically stunned sheep, goats, pigs and ostriches, a “grand mal”6 seizure is induced which causes instant unconsciousness. This results in rigid spasms, which can last for up to 30 seconds. The animal should not be evaluated for insensibility until at least 30 seconds after electrical stunning. At no time after stunning should the animal vocalise (squeal, moo or bellow). Vocalising is a sign that the animal can still feel pain. It is normal to have leg-kicking reflexes in an animal that has been properly stunned with electricity, captive bolt or gunshot. If the animal has kicking reflexes, the head should flop like a rag doll. If it makes an attempt to raise its head, it may still be sensible. An animal showing a righting reflex must immediately be re-stunned.

6 A “grand mal” seizure is a severe form of epilepsy characterized by paroxysmal transient disturbances of the electrical activity of the brain. This results in periodic recurrent convulsions of the body or “epileptic fit”.
The person assessing insensibility should concentrate on looking at the head and ignore kicking limbs. Gasping is permissible: it is a sign of a dying brain. If the tongue is hanging straight down, limp and floppy, the animal is definitely stunned: if it is curled this is a sign of possible sensibility.

The heads of poultry that have been stunned with electricity should hang straight down after stunning. Birds that have not been properly stunned will show a strong righting reflex and raise their heads.


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