Module 6. Meat and poultry processing

Lesson 21

SLAUGHTERING TECHNIQUES AND POST-MORTEM INSPECTIONS

21.1  Slaughtering Procedures

After the animals have been rested for sufficient time, they are quietly taken to the stunning area. Animals may be facilitated through mechanical means like canvass straps or rolled plastic or prodded to move forward. However tail twisting or beating is forbidden. Slaughter animals are properly restrained before stunning or bleeding. Different types of restraints are used for different species.  

21.1.1  Stunning

It is a process to inactivate animals so that it is not able to move. It is an obligatory process with large animals. Stunning ensures that the animal is unconscious before it is slaughtered in order to eliminate pain, discomfort and stress from the procedure. Many countries have legislation that requires pre-slaughter stunning. Care should be taken not to affect the heart and it should function normally to ensure complete bleeding which ensures better meat quality. Stunning is done in special stunning pan (box with movable side wall).

21.1.1.1  Stunning methods

1. Most common method employed is striking on the head with a wooden hammer or captive bolt. However blow should not damage the frontal bones as it may cause brain hemorrhage.

2. Electrical stunning: An electric current of 75-120 volt is passed for 15-70 seconds through the hind part of the animal head in the regions of parietal boxes by puncturing the skin. This causes unconsciousness of the animals which may last for 5 min and it is enough to transfer the animal from stunning pan to bleeding runway.

3. Anesthetization: Anaesthetization may be carried out on swine using a mixture of CO₂ and air in equal volume with 0.18% chloroform and the inhalation period may last for one min.

21.1.2  Slaughter

The most common methods of slaughter practiced worldwide are the Halal (Islamic), the Kosher (Jewish) and the Jhakta (Sikh) methods.

Halal: Halal is one of the most popular method of slaughter. This method prescribes slaughtering of animals with a sharp knife to make a swift, deep incision that cuts the front of the throat, the carotid artery, wind pipe and jugular veins but leaves the spinal cord intact. The animal is then hung upside-down and left to exsanguinate i.e drainage of blood. The Halal slaughter requires that the name of Allah (or God) should be mentioned at the initiation of the operation. This method of slaughter ensures that the blood flows out completely from the animal.

Jhatka: It is an instant decapitation process limited mostly to sheep and goats and practiced in countries like India by few religious sects. The animals are killed by a single strike of a sword or axe by severing the head Jewish Slaughter (Kosher): “Kosher” is the term applied to the procedures and techniques of slaughter practiced under the Jewish faith. In Hebrew language, Kosher means fit to be used as food. Under this method of slaughter, the animals in fully conscious state are killed and bled thoroughly by one clean stroke of the knife. Animals are however hoisted and shackled first. A 16-inch (40.6 cm) razor-sharp steel knife called the chalaf is stuck into the throat by a trained slaughterer, the shohet, in an operation in which the animal is killed and bled at the same time. Skinning is made from the chest down to the level of the belly, and the chest is cut open first for inspection and later evisceration.

21.1.3  Bleeding

Bleeding is a procedure in the slaughter process which is performed by cutting jugular vein in the neck and carotid artery in order to allow blood to drain from the carcass, resulting in the death of the animal from cerebral anoxia. The bleeding knife should be continuously sharpened as a blunt knife may prolong the incision and damage the cut ends of the blood vessels. This may result in premature clotting and blockage of the vessels thus delaying the bleeding process. A prolonged delay in bleeding could result in the animal regaining consciousness. The delayed bleeding may also result in an increase in blood pressure causing the blood vessels to rupture and haemorrhage of muscle. The extra blood in the tissues may lead to meat getting decomposed quickly. Incisions should be therefore swift and precise. In poultry, sheep, goats and ostriches, the throat is cut behind the jaw.  

21.1.4  Skinning

After successful bleeding, first the head is skinned, separated from the body, marked with the same number as the body and then hung on hook for post mortem examination. ‘Skinning’ is a term mostly used for small ruminants and the method of skinning is known as “case-on”. The skinned materials are called as “skins”. Skin is the most valuable byproduct economically. In sheep and goats, skin is first cut around the leg to expose and loosen the tendon of the hock and used for hanging the carcass. This process is called legging. The second step that follows is called skinning which involves removal of the entire skin and preparation of the animal body for evisceration. Skinning can be done either in the horizontal or hanging position depending on the convenience and available facilities. If animal body is in hanging position, legging is generally started at the back of the free leg by removing the skin around the hock and continued towards the toes. This exposes the tendon on the back leg and the foot is cut off at the joint above the toe. The body skin is removed by making an opening in the front legs, cutting towards the jaw and continuing over the brisket to the naval. Once the brisket has skinned, knife is seldom used to protect the “fell” (a fine membrane between the skin and the carcass). This helps in improving carcass appearance and reducing surface shrinkage. This is largely accomplished by using fist/hand. After the skin has been removed, the carcass is washed and placed on a hook. In horizontal skinning the animal is placed on its back on a flat raised surface and similar process repeated.

This operation is absent in pigs, because skin is a part of the carcass. In the case of large ruminants (cattle and buffaloes), cuts are made on the skin along the mid-ventral line and also on the medial side of the limbs connecting to the respective points (sternum and pelvis) in the mid-ventral line. Skinning of large ruminants is known as “flaying” and the incisions made on the skins are known as “ripping lines”. The deskinned materials are called as “hides.

21.1.5  Evisceration

It should be carried out without damaging the internal organs or disturbing the internal surface of the carcass. Damage to the gastro-instestinal tract (GIT) may contaminate the carcass with the microorganisms. The first step in evisceration is to cut around the tied bung or rectum and free it completely from all attachments. The breastbone is then cut along the midline up to its tip. Another cut is made from the cod or udder down the midline into the breast cut. Then the ureter connections to the kidneys are severed and the intestines loosened. The stomach and intestinal mass are removed. The lever could be detached from its connecting tissues and then pulled out along with the contents of the abdominal cavity. The gall-bladder is carefully removed from the liver so that its content does not spill out and contaminate the carcass. The pluck consisting of heart, lungs, trachea and esophagus can be pulled out as a unit. The carcass is then washed and carried manually or mechanically to the inspection area.

21.1.6  Carcass splitting and sizing

In the slaughterhouses, carcasses of small ruminants are not split into sides or quarters; carcasses of large ruminants are split into four quarters; and carcasses of pigs are split into two sides. Therefore, at the retail meat stalls selling buffalo meat, pork and mutton, we find quarters, sides and whole carcasses of respective animals. Carcasses are sawed by electric or pneumatic saws starting from the hind part to the central vertebrae. This facilitates transport, storage and efficient refrigeration. 

21.2  Post Mortem Examination

Postmortem examination/inspection refers to inspection of carcass and organs by qualified veterinarians to ensure that carcass and organs are fit for human consumption. During inspection, care should be taken not to contaminate the carcass and organs from diseased animals. The knives and other instruments used for cutting and examining organs, glands and tissues should be properly sterilized before and after use. The particular sequence should be followed during postmortem examination so that each carcass and thereof organs are checked thoroughly.

21.2.1  Objectives of postmortem examination

Carcasses should not be sent to the chilling section without inspection after dressing. Some of the diseases are not apparent during ante mortem examination can be detected easily in postmortem examination. Thus, post mortem inspection ensures safe meat to the  consumers and also controls diseases right at the farm level itself. It also directs to adopt a proper disposal procedure for condemned meat and offal. Since postmortem inspection is performed for carcasses as well as their viscera, it ensures a systematic way of evisceration and handling of offals.

21.2.2  Facilities required for postmortem examination

· The area where the examination is being conducted should have sufficient and well distributed light. The natural light is considered better than artificial light. The intensity of light must be 540 lux

· The person carrying inspection need clean, sharp, stainless knives

· There must be provision for hot and cold water

· There should be a sterilizer to sterilize the knives, saws and cleavers. The postmortem examination should be carried out under hygienic conditions. The knives should be sterilized by dipping them in boiling water for 30 minutes or by autoclaving them for 10-15 minutes. (The sterilization of anthrax contaminated knives requires special consideration).

· To put a mark on carcass and its viscera, marking dyes should also be provided, which should be cheap, non-toxic and non-corrosive in nature. Marking indicates that the carcass has been inspected and guarantees the consumer about is wholesomeness. Marking of meat is done by (i) using a stamp (ii) branding or (iii) labeling. Common method – Metal stamp dipped in a stamping ink.

· There should be provision of detained room side by the inspection site.

21.2.3  General consideration

Following points should be considered during postmortem examination/ inspection:

· The examination must be done as soon as possible. Carcasses of beef and pork set rapidly and if the inspection is delayed especially in cold weather the examination of lymph nodes becomes difficult.

· Carcass and organs are to be examined methodically following a definite sequence. Healthy carcass should be examined before inspecting the diseased or suspected ones.

· Great care must be taken at the time of inspection particularly in cases suspected for zoonotic diseases.

· The identity of carcass and its viscera should be maintained.

· Inspector should avoid unnecessary cuts considering the value of high quality food. One should incise the carcass in such a way that the surface of the carcass appears clean and undistorted.

21.2.4  Postmortem  principles

21.2.4.1  Visual perception

First the carcass and visceral organs should be examined visually for any visible abnormalities. Examination is done for any change of colour, atrophy, hypertrophy, neoplastic condition etc.

21.2.4.2  Palpation

The organs are palpated for any change in consistency, sliminess or gelation, cyst, etc.

21.2.4.3  Incisions

The organs are incised, if needed. This is done to examine any parasite inside organ, structural deformity etc.

21.2.4.4  Laboratory tests

These are done for confirmation and support the observation made by macroscopic examination. While examining the organs of carcass, lymph node of adjoining area must be examined.

21.2.5  Postmortem Examination of Carcasses

21.2.5.1  Large animals

In case of large animals like cattle, sequence of postmortem examination is as follows:

Head

· Verify the number, age and sex of the animal

· Inspect gums, lips and tongue for FMD, necrotic and other forms of stomatitis, actinomycosis and actinobacillosis (Palpate the tongue for the latter).

· Incise the internal and external masticatory muscles and tongue for Cysticercus bovis.

· Incise retropharyngeal, submaxillary and parotid lymph nodes for tuberculosis (TB) lesions.

• For sheep & goat, the lips, gums and nasal cavities should be examined for contagious ecthyma.

Lungs

· Examine visually and then palpate for the detection of pleurisy, pneumonia, tuberculosis, fascioliasis and hydatid cysts.

· Incise the bronchial and mediastinal lymph nodes and expose the lung by giving deep incision from the base to apex (for checking TB lesions).

· Check the tumors, abscesses etc. by palpation.

Heart

· Examine the pericardium for traumatic or tubercular pericarditis.

· Incise the ventricles of the heart and pay attention to look for petechial hemorrhages on the epicardium and endocardium and cuts in the myocardium. Flavy condition of the myocardium is indicative of septic conditions.

Liver

· A visual examination should be made for fatty changes, abscesses, hydatid cysts, actinobacillosis etc.

· For examination of fascioliasis, incise thin portion of left lobe of liver and examine the contents.

· For sheep and goat, lungs, heart and liver:

(i) Palpate lungs, heart and liver and accompanying lymph glands for abscesses.

(ii) Cut the bile duct for examining possible fluke infestation

Stomach and intestines

· Check the serous surface of the intestine for TB lesions and actinobacillosis.

· Palpate the mesenteric lymph node and if necessary incise and examine the same.

Spleen

· Examine the surface and substance for TB lesion, anthrax, hematoma and presence of infarcts.

Uterus

· Check for septic conditions by viewing, palpating and incising if necessary.

Udder

· Check the supramammary lymph nodes by incising for the evidence of TB lesions.

· Check for abscesses if any.

General inspection of carcass

· Look for the injuries and bruises. Bruises are dark colour after 24 hours and there is watery condition after 24 to 38 hours. After 3 days, the area becomes rusty orange colour and soapy to touch.

· Look for inflammation, abscesses and TB lesions in the thoracic and abdominal cavities.

· Examine the kidneys.

· Incise and examine renal lymph nodes.

21.2.6  Postmortem judgement

Similar to ante-mortem examination, a competent veterinarian has to submit its judgment report:

· Fit for human consumption

· Unfit for human consumption or total condemnation

· The affected organs must be condemned while rest can be passed for human consumption (partially condemned).

• The condemned carcass/ organs should be disposed off following scientific procedure.

21.2.7  Diseases and conditions for which carcass is totally or partially condemned

The carcass is totally condemned for rabies, anthrax, glanders, rinderpest, foot and mouth disease, acute enzootic meningoencephalitis, acute pleurisy, contagious bovine pleuropneumonia, ovine foot rot, sheep pox, swine fever, swine erysipelas, salmonellosis, fibrinous rhinitis, black leg, bovine viral diarrhea, haemorrhagic septicaemia, listeriosis, pasteurellosis, coccidiosis, calf diphtheria, calf diarrhoea, malignant oedema, tetanus etc.

The carcass in case of actinomycosis, actinobacillosis and Johne’s disease, is totally condemned if accompanied with emaciation and in generalized form, otherwise the carcass is passed for human consumption after local condemnation. In case of corynebacterium infection, carcass is passed after removal of affected organs.

In case of heavy infestation (more than 10 cysts) with Cysticercus bovis and Cysticercus cellulose, carcass is totally condemned, otherwise the carcass is passed after removal of head, heart, diaphragm and esophagus. Trichinella spiralis infected carcass is totally condemned. If carcass show the sign of fascioliasis with emaciation then it is totally condemned, otherwise it is passed after trimming of liver.

Carcass is passed for consumption after removal of lung in case of emphysema and broncheolitis. If there is no fever, then carcass with sign of gastroenteritis is unconditionally passed.

The judgement of carcass suffered from tuberculosis depends on method of spread, extent of disease, character and age of lesion and general condition of the animal. Carcass is totally condemned when tuberculosis spreads through portal or pulmonary or systemic circulation. In case of localized tuberculosis, the carcass is passed after removal of the affected organs and associated lymph nodes.

21.2.7.1  Metabolic and nutritional disorders and intoxication

The carcasses are totally condemned if they show any of the following sign:

Anaemia with emaciation, (ii) grass tetany, (iii) haemoglobinuria, (iv) jaundice, (v) ketosis with chronic indigestion, (v) poisoning, (vii) bloat or (viii) impaction etc.

Abnormal conditions: Abnormal conditions like, abnormal colour, taste and smell, buck smell, bore smell etc. results in total condemnation of the carcass.