ANIMAL| STUNNING TYPES, PROCESSES AND PROCEDURES.

 

INTRODUCTION.

The aim of stunning is to render the animal unconscious as soon as possible so as to prevent pain and suffering during the killing process. The stunning process ensures the animal is unconscious and insensible to pain before being bled out at slaughter. Common stunning methods include electrical stunning. The animal must remain unconscious until death. The need for stunning is acknowledged all over the world, and no slaughtering may be done at an abattoir unless the animal has been stunned in the approved manner.

Whether stunning is to be achieved by means of electric or captive bolt apparatus, the apparatus concerned shall be examined and tested before use each and every day it is to be used, and at

TYPES OF STUNNING.

1.      CAPTIVE BOLT STUNNING

The contact-firing types of captive bolt pistol are much more satisfactory than the trigger-operated ones, only a light tap on the animal’s head being necessary to fire them. They are quicker and easier to operate and can be loaded and fired 10-12 times a minute. However, if they are dropped on the floor or struck against the stunning box wall, the whole gun can become a dangerous missile. A defect of percussive stunning and the use of the free bullet is noise. Most of the really serious defects, however, arise from misuse or from instruments in poor state of repair, as is the case with all forms of stunning. The European Directive on the Protection of Animals at the time of slaughtering makes it a responsibility of the Official Veterinarian to ensure that the instruments used for stunning, and for restraint, are in a good state of operation. The importance of regular maintenance if the pistols are to function correctly cannot be overemphasized. The velocity of the bolt may be significantly reduced by a build-up of carbon or corrosion on the pistol, which drives the bolt forward, or by excessive wear in any of the moving parts. While some manufacturers recommend cleaning every 70 shots, daily dismantling and thorough cleaning must be carried out. A common indication that a pistol requires cleaning is the tip of the bolt protruding from cleaning from the muzzle more than the usual distance between shots.  The tendency on the part of many operatives to stun a group of animals, especially sheep, before bleeding, this obnoxious practice should be avoided which leads on occasions, to recovery of consciousness and a high incidence of blood splashing. All forms of mechanical stunning devices should be fitted with safety levers to minimize the chances of accidents and should be easily cleaned and maintained. It is vital that the impact end of the penetrating type be kept sharp. A back-up pistol should always be on hand in cases of emergency. 

2.      ELECTRIC STUNNING.

A low voltage alternating current is passed through the brain of animal, rendering it instantaneously unconscious in which state, it remains for about 5 minutes during which time it can be hoisted, removed to the bleeding section and bled. Different types of electrical stunning systems in use;

1. manually operated and
2. automatically operated, especially in pigs and poultry.

The instrument that is most commonly employed resembles a pair of tongs. This is to make the animals unconscious before they are bled. Now mostly used for pigs, poultry, sheep and pigs. The great advantage of this method is that there is no squealing, struggling or kicking and no sound of a shot. The current causes massive depolarization of neurons in the brain, resulting in an epileptiform seizure. Electrical stunning was first introduced in the 1930s. But there is still a lack of knowledge on its efficiency in producing insensibility. It must be agreed that if certain requisites are not complied with the method may be inhumane, for the electrical current may produce a condition known as ‘missed shock’ in which the animal, though paralysed, is fully conscious. The electrical stunning may be regarded as efficacious and humane method in as much as it causes incoordination of the cerebral nerve cells and what may be aptly defined as a confusional state of the brain.

ADVANTAGES OF  ELECTRICAL STUNNING.

• The continued function of the heart and maintenance of the arterial blood pressure (at a higher level than when animals are stunned by captive-bolt type instrument)
• The nature of the muscular contraction, which expels the maximum amount of blood from the skeletal, muscles in a manner similar to the squeezing of a sponge. 
•  The violent and incoordinated muscular contractions are noticeably absent after electrical stunning and during the act of sticking.
• The efficacy of electrical anaesthesia is dependent on the total quantity of electrical energy supplied, expressed in watt-seconds rather than the individual factors of voltage, amperage or time.

 

3.      STUNNING BY USING MECHANICAL DEVICE.

 In course of newer inventions and sophistications in stunning devices, the following methods which were in practice in early days were obsolete now-a-days. Moreover, to the provisions of animal welfare some of the methods were considered to be more inhumane and cannot be permitted as a part of humane slaughter in the form of animal stunning.

3.1 HAMMER MALLET OR CLUB.

In some cases a hammer does stunning. In the case of small animals, a mallet or club is also used. These are not advocated for the following reasons. A hard blow on the head with a hammer may kill the animal outright but a clumsy workman may require repeated blows to attain his purpose.

3.2. POLE AXE

This is extensively used in Scotland in the hands of really expert operator. It is astonishing to see how quickly the animal is killed and how seldom the aims missed. That part of the weapon, which is the actual killing structure, is an elongated iron bar at the back of the axe, which is fixed in a strong wooden handle. When properly used the instrument never fails to produce immediate unconsciousness in the animal (Frazier, 2008). The bore made by the penetrating portion is sufficiently large to admit the pithing rod and which is applied directly after the axe is withdrawn. The head is secured and immovably fixed by after the rope to an iron ring in the wall. After the pitching the animal is perfectly still and is immediately ready for bleeding. Killing depends upon the accuracy of the arm.

3.3 THE GOTHENBURG'S SWINE KILLER

It is the most satisfactory method of rapidly dealing with the animal. This is only a method of securing in a position where struggling is eliminated and the actual method of killing is not part of this invention. It contains of an oblong iron chamber into which the pig enter directly from the yard through the wall, which is then closed from behind. At the other end in the front wall, the pig puts its head and is then enable to withdraw when the chamber is closed.(WHO,2010).

3.4. THE DUTCH PIG TRAP.

It is equally satisfactory for the same purpose, used in the principal abattoirs in Holland. The principal is the same.

3.5. NECK STABBING

This is one method of slaughter largely used in Africa, India and Australia. It consists essentially in dividing the spinal cord with a long sharp point knife, which is thrust into the neck of the animal between the first cervical vertebrae and the occipital. This immediately renders the animal paralyzed, but does not immediately destroy consciousness. Bleeding is done as soon as the animal falls down. (WHO, 2005).

PROCEDURES AND METHODS 0F STUNNING.

1.      CATTLE.

There are two main types. The most widely used has a bolt, which penetrates the skull. The other has a mushroom-shaped head, which stuns the animal by concussion. The pistol can be fired by cartridges or air pressure. Correct stunning points for various species Cattle Aim for the point of intersection of two imaginary lines running from the highest point of each eye to the lowest point at the base of the opposite horn. The barrel of the pistol should be placed firmly against the skull and at right angles to the head. In old or heavy cattle the ridge of bone down the centre of the face must be avoided. (FAO, 2005).

Place the barrel 1 cm to one side of the ridge. People who use a captive bolt pistol for stunning cattle must know where to stand. The operator must never stand in front of the animal, as it will jerk its head away when the pistol is aimed. The best position for the operator is just behind the animal's head. When it looks up, the pistol can be quickly brought into position and fired. A light above the stunning box encourages the animals to look up. Tapping an animal on the back or making a sound to attract its attention will usually make it look up. A mistake frequently made is to try and follow the moving head with the pistol. The best method is to wait until the head is fairly still, and then to use the captive bolt pistol in one movement like a striking snake.

 Calves Same as for cattle. Aim for a slightly lower point, however, as the upper part of the brain is not as well developed as in adult animals.

SHEEPS AND GOAT.

 Hornless: Place the pistol against the highest point of the head above the base of the ears and aim towards the throat.

Horned: Aim behind the centre of the ridge between the horns, with the barrel pointing towards the mouth. Goats As for horned sheep.

PORCINE.

 Aim about 2 cm above eye level, on the middle line, and aim upwards and into the head. A properly stunned animal should have no eye reflexes. The head must be completely relaxed and incapable of movement. The ears must flop and the tongue loll. Electric tongs Correct stunning points for various species As we have mentioned, this is the method of choice for pigs, sheep and goats. It would appear to be used for cattle as well in some overseas abattoirs. (Wilson).

The correct positioning of the electrodes is very important. Proper electrical stunning depends on the maximum flow of electricity through the brain. For pigs the best position is on either side of the head, under the ears and level with the horizontal line through the highest point of the snout. A similar position also applies for sheep and goats (Frazier,2008). Apart from the correct positioning, the following factors also play an important role in determining the level of effectiveness of electrical stunning:

1. The voltage. This must be high enough to overcome the resistance of body tissue.

 2. The amperage. This is the most important factor; it causes depolarisation of nerve tissue with consequent loss of consciousness.  This is usually 2-4 seconds for calves, goats and sheep and 2-10 seconds for pigs.

 4. The frequency of the electric current.

5. The condition of the electrodes, for example sharp or blunt.

The pressure with which they are applied. A dry or wet skin.

Proper electrical stunning will cause the animal's legs to collapse, so it will fall. Next there will be stretching of the legs and upward bending of the neck. Paddling movements of the feet may occur. If the neck arteries are not severed, the animal will later regain consciousness. The amperage and voltage will vary according to the type of equipment and the size of the animal. In general a current of 0,8-2 A is used for all animals, while the voltage will vary from ±110 volts for a small pig to 250 volts for a large one.

RIGOR MORTIS AND IT’S IMPORTANCE.

Rigor mortis is also called "death stiffening". It is stiffening of muscle and is also an important post mortem change. It is known that a particular level of ATP complexed with Mg+ is required for breaking the actomyosin bond and bringing the muscle to relaxed state and it drops permanent actomyosin cross bridges begin to form and muscle gradually become less and less extensible under an extremely applied force. Rigor mortis is important in meat products since muscle cooked while still in rigor are are much tougher then if it is allowed to pass before cooking (WHO,2000). Rigor mortis occurs in 3 phases, the extent and contraction of muscle contraction is as shown in figure1. The 3 phases of rigor mortis development are :

 1. Delay phase

 2. Onset phase:

3. Completion.

After the passing of rigor mortis, meat become more tender and jucier and flavorful. Rigor mortis in muscle tissue is usually resolved 2–3 days post mortem. By this time, the meat again becomes soft and tender (in case of beef especially). Further aging of the meat to improve tenderness and to form aroma requires various amounts of time, depending on the temperature.  At temperatures around 3 ◦C (−1 ◦C to +7 ◦C), aging of poultry requires at least 36 h, pork 60 h, veal 7 days and beef 14 days.(FAO, 2008).