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In rural areas of developing countries the slaughter of animals for meat consumption is often carried out under less than ideal conditions. Where there are no facilities, slaughtering is likely to take place under a convenient tree where an animal can be hoisted for skinning and evisceration. Meat produced under such conditions lacks veterinary inspection, is often contaminated and must be considered a hazard to human health.
Most countries will have a meat control act providing meat inspection aimed at the control of meatborne diseases and the protection of the consumer from meat of inferior quality or that has not been hygienically slaughtered and handled. The act may state minimum requirements for the design and operation of slaughtering facilities and must Therefore be carefully studied before any construction commences. While only basic design requirements are discussed here, the throughput and sanitary conditions of a slaughterhouse also depend greatly on equipment, manpower and work organization. It is advisable therefore to seek the advice of specialists whenever a slaughtering facility is to be planned, especially if the required killing capacity is more than a few animals per day or other facilities such as meat processing are to be included at the same location.
Gantry Hoist
In areas where population density is low and relatively few animals are slaughtered, a simple and inexpensive slaughtering facility is desirable. As animals must be hoisted immediately after stunning to assure proper bleeding and then remain in a hanging position during the dressing operation to ensure sanitary conditions, a first step in improving facilities is to build a wooden or steel gantry hoist. While a single gallow should be at least 3.7m above floor level, two levels of suspension are desirable; 4.5m for bleeding of cattle and 3.5m for the dressing operations. Sheep and goats can be suspended from a rail at a 2m height at the side of the gantry hoist.
Although a mobile gantry hoist that can be easily transported and reassembled is feasible in the first stage towards improved slaughtering, a permanently installed facility will normally be the minimum requirement as that allows for the construction of a concrete floor and a metal roof. The roof gives protection from sun and rain and allows slaughter to take place in all weather.
Figure 10.62 Homemade feeder, waterer and kindlingbox.
Whether temporary or permanent, the site should be fenced to prevent access to stray animals and unauthorized persons. In particular dogs and jackals must be prevented access to offal and condemned meat. These products may contain the parasite causing hydatid disease and infected dogs are a very common means for disseminating the disease to man.
Slaughterslabs
After an initial installation of a gantry hoist, concrete slab and metal roof, the facility can be gradually converted to an economical, low through-put slaughterslab. There should be floor rings to hold animals, skinning cradles for cattle and small stock, rails for hanging the carcasses and an adequate and convenient water supply.
Satisfactory waste disposal is a requirement from the start. The slab can be surrounded by wall 1.5m high and partitions can be installed between clean and dirty operations areas. A lairage should be constructed for both cattle and small animals. Drinking water should be available for the animals at all times.
Paving the area immediately surrounding the slaughterslab with either concrete or bitumen will improve both sanitary and working conditions. An extended overhead rail will allow the carcass to be moved from one operation to the next until it reaches the despatch area. Improved sanitation and management are possible by using separate bays for cattle and small stock. However, this is a design feature that must be considered at the very onset when the floor slab is poured.
Slaughterhouses
In areas where a large number of animals are slaughtered a fully equipped slaughterhouse should be provided, i.e. a large slaughter hall where animals are stunned, bled, slaughtered, flayed and dressed in successive operations. In such a system live animals enter one end of the building and emerge as dressed carcasses at the other. Capacity can be increased by using more than one bay for each kind of animal. A freezing room is normally included in a slautherhouse, but only the largest factory abattoirs will have facilities for the processing and large-scale storage of meat, and the utilization of inedible byproducts.
Figure 10.63 Gantry' Hoist and layout of fenced area. (By courtesy of Dr. 1. Mann).
Pig Slaughter
Out of consideration for the Muslim population, pigs should be handled separately in a slaughterhouse designed and used only for that purpose. Reasons other than religious also make it desirable to separate pig slaughtering. The steam from the scalding vats creates adverse conditions for setting of meat and the scurf accummulated from scraping pig carcasses is heavily contaminated with meat spoilage organisms. Pig slaughterhouse designs follow the same basic pattern as those for cattle, with provision for the separation of clean and dirty activities. The gallows and rails need to be 3.9m above floor level in the bleeding area and 2.5m in the slaughterhall. A water boiler to supply the scaldingvat with water of about 80°C will be required.
Poultry Slaughter
Most poultry for local meat supply in rural areas is slaughtered singly or in small batches as the need arises and it is often carried out in the kitchen.
Only in areas where poultry is produced on a medium to large scale for supply of meat to an urban area, will the construction of a slaughterhouse for poultry be feasible.
General Recommendations for Design and Construction
The site for a slaughter facility should be on ground that is higher than its surroundings to facilitate drainage. An adequate water supply must be available nearby to allow the slaughtering operations to be carried out under sanitary conditions. An all weather road will ensure timely dispatch of the meat throughout the year. All trees and bushes within 20m of the fenced area should be cleared to detract birds, insects, etc.
In tropical countries slaughterhouses should be as open to the air as possible and the building designed so that even a light breeze will produce a ventilating draught. The openings should not be glazed, but should, along with grills in the roof ridging, be screened to prevent the entry of insects. The grills will allow the warm air to escape and cooler air to be drawn in through the windows.
For sanitary reasons, floors and walls should be easily cleaned, impervious to water and rodent-proof. Concrete floors should be finished smoothly, but not to the extent of being slippery, and sloped towards the open drains along the walls. Concrete blocks or stone building blocks are preferred for wall construction. All joints should be smoothly finished and wall and floor junctions will be much easier to keep clean if they are finished with a cove.
Figure 10.66 Pig slaughterhouse for 20 to 30 animals per day.
The meat must not come into contact with any wooden surfaces or equipment. Steel is prone to rust and stainless steel is generally very expensive. Hence concrete could be used wherever practicable and in particular for such items as troughs for intestines, offal, and for work benches. If wood is used for doors, a galvanized steel sheet should be fixed to the bottom of the door on the outside for protection against rodents. The layout should be designed to permit expansion without basic alterations to the original structure or suspension of operations. See figure 10.68.
Lairage
A lairage with a capacity of 11/2 days kill should adjoin the slaughterhouse. Here the animals are allowed to rest and recover from stress before slaughter, thereby improving the setting quality of the meat. Each pen in the lairage should hold about 15 cattle allowing at least 2.3m² for each animal. At least 0.6m² should be allowed for small animals. While the lairage should be an integral part of the slaughterhouse complex, it should be separated by at least 10m and connected by a long, straight cattle race 75cm wide at the top, narrowing to 45cm at the bottom, to prevent the cattle from turning around. The lairage should provide shade and clean drinking water and a hard, impervious, well-drained floor sloping toward open drains. A separate area where animals showing signs of sickness or fatigue can be detained for control, is desirable. A holding pasture where the animals are allowed to graze until 24 hours before slaughter should be available. A clean lairage ensures that the animals will enter the slaughtering area as free as possible from contamination.
Water Supply
Obtaining an adequate supply of potable water will often be the greatest problem to overcome when constructing a slaughterhouse in a rural area. The following minimum quantities should be available for each animal slaughtered:
1000 litres - cattle
100 litres - small animals
450 litres - pigs
Water from wells is best, but in many cases it will be necessary to use water from lakes and rivers. Should the quantity of potable water be insufficient, it may be necessary to install a dual water system, the potable water being used for carcass and edible offal, and non-potable water for watering stock, washing skins, cleaning, etc.
If a water tower is required, the simplest procedure is to purchase a prefabricated steel tank of the correct size. If, on the other hand, an underground tank is installed, it can be made of reinforced concrete. In the event that it is impossible to provide a supply of potable water, it is preferable to use a 'dry' slaughtering method, ensuring that no water comes in contact with the meat. However, the dry kill method should be used only when a maximum of two animals per day are killed. Water will still be needed for washing floors, walls, etc.
Figure 10.67 Slaughterhouse for Poultry.
Figure 10.68 Slaughterhouse with essential facilities.
Disposal of Blood
The large quantities of blood collected from the bleeding area should not be allowed to enter the main drainage system and cause pollution, and must not be mixed with water. Therefore, all the effluent from the stunning and bleeding area should be collected separately and led to an underground tank situated outside the building. The tank should be built with a tight-fitting, removable cover and be so constructed that the liquid can seep through the sides into the surrounding soil. the blood will eventually decompose and it should be necessary to clean the tank only occasionally.
To avoid objectional odours, the tank should be equipped with a screened ventilation pipe. In tropical areas the air in the pipe and the upper part of the tank will be warmed sufficiently during the day to cause circulation and air renewal in the tank.
The blood tank will operate satisfactorily only if the ground water level is below the level of the tank and the surrounding soil is pervious to water.
Removal of Manure and Condemned Meat
The carcass should be dressed out rapidly and the offal inspected and taken to a separate room where it can be cut up and the stomach and guts opened, cleared of manure and flushed with water. The manure is taken to a manure pit outside the building, while the rinsing water is directed into the main drainage system.
Suspected or condemned material is taken to the room set aside for this purpose. At the end of the day it is disposed of, together with inedible offal, in two concrete pits outside the building. The pits should be equipped with airtight locable covers.
Most of the material will slowly decompose and it will not be necessary to empty the pits. Incineration is not recommended as efficient incinerators are expensive both to buy and to operate and simple incinerators do not work satisfactorily and burn out quickly.
Drains
As running water is used during slaughtering and floors are flushed clean, the floors should be sloped so that water and effluent run into open drains placed along the walls. All these drains should be connected by a central drain to a grease and solids trap. From this trap the remaining effluent is led either into an evaporation pan where bacterial action will break down most of the effluent in 20 to 30 days, or alternatively, into a sub-surface seepage field, designed with a series of herringbone patterned trenches filled with stones.
Soakage pits not less than 6m deep and 1.8m in diameter and covered with a concrete top are satisfactory for only the smallest units.
Open drains are recommended for the effluent from the slaughterhouse for the following reasons:
To prevent rodents from entering, a screen should be fitted to the open drain where it passes through the slaughterhouse wall in such a way that it can be easily removed for cleaning.
Cooling, Chilling and Freezing Rooms
As soon as the carcasses have been dressed they should be removed from the slaughterhall to avoid prolonged exposure to its atmosphere and thereby reduce the development of microflora in and on the meat. Most meat in the tropics is distributed, still warm, for consumption the same day it is slaughtered. Hence a cooling room will normally not be required. The meat is instead transferred directly to a dispatch area. This practice implies that the work must start sufficiently early, and the slaughterslab, or slaughterhouse must have capacity such that the slaughtering operations can be finished by about 10 o'clock in the morning.
It is desirable to have a freezing room in all but the smallest slaughterhouses. The freezer can be used to sterilize measled meat, since some types of meat parasites are destroyed by the low temperature. It also makes it possible to help to balance the supply of meat to the demand. Refrigeration units are expensive and a chill room where meat can be ripened and tenderized can be justified only where there is a demand for meat treated in such a way.
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