|
|
|
Humane destruction and disposal of stock
Agnote DAI-136, first edition, December 1999
Ross Burton, Veterinary Officer (Animal Welfare), Orange
Tough times may force many stockowners to consider on-farm disposal of animals that have no commercial value, or on animal welfare grounds as a result of bushfires, storms, flooding or drought.
This disposal must be conducted humanely, efficiently and safely.
If euthanasia of animals is considered necessary, all bystanders should be asked to move on, and every effort should be made to keep the procedure out of view of members of the public to avoid causing distress.
Experienced operators using the techniques described in this Agnote can handle more than 1000 sheep or 300 cattle per day.
Methods for humanely destroying stock
Methods for humanely destroying stock include the following:
- Shooting: This is generally the best choice as it is quick and painless when carried out correctly. Legal considerations regarding the use of firearms must be observed.
- Lethal injection: Can be administered only by a veterinarian, and is impractical for large numbers.
- Cutting the throat: May be used as a last resort for sheep only, and should only be carried out by an experienced operator.
Wherever possible, first contact abattoirs and knackeries to establish the economics of slaughter through these outlets. However, in many cases, the costs of transport and slaughter may exceed the value of the stock. It may also be inhumane to transport severely affected stock.
Methods of on-farm disposal need to be costed in order to compare the alternatives. On-farm disposal usually costs $1–$2 per head if machinery is hired.
Safety must be considered at all times:
- There should always be at least two people at the pit disposal site—psychological support is essential.
- Rescue items, such as ropes, should be available in case the pit wall collapses or someone falls into the pit.
- Planned, methodical use of guns and knives should be determined, with non-operators strategically located to avoid accidents.
- Personal hygiene factors must be taken into account, especially if the animals are diseased. Scabby mouth, anthrax and Q fever can be contracted by humans from animals, from their carcasses or from their blood.
- Earmuffs and protective clothing should be used when necessary.
Burn or bury?
Burning is not usually practical due to the amount of fuel required, possible restrictions on the lighting of fires, the risk of fire getting out of control, and the labour involved. Burial is invariably quicker, easier and cheaper.
Advice should be sought from local earthmoving contractors regarding the type of machinery available for the digging and bulldozing, and the machinery operating costs. In some cases, farm machinery can do the job.
The position selected for the burial site should comply with the following:
- The burial site should be at least 100 m from any watercourse.
- Sites which slope towards a watercourse should be avoided.
- The base of the pit must be at least 1 m above the watertable.
- Access to the site for earthmoving machinery and either stock transports or walking stock must be considered.
- The soil should be heavy, and should have low permeability and good stability.
- Appropriate diversion banks should be constructed in order to prevent stormwater entering the pit and consequent diffusion of contamination from the site.
- One long side of the pit should be kept clear of overburden, and should be levelled. This side can be used for the killing area, with appropriate pens and races built of moveable panels or temporary fences (see Figure 1). Soil should be placed at the ends or along one side of the pit.
Figure 1. A suggested layout for the killing pens and holding yards, using moveable panels and temporary fencing
Pit construction
The dimensions of a suitable, vertical-sided pit will vary according to the number and size of the animals and the type of equipment available to construct the pit. Excavators, bulldozers and front-end loaders/backhoes are all suitable.
During construction, topsoil should be separated from subsoil for later return to the top during pit closure.
Surplus soil should be heaped as overfill, to form a mound over the pit.
Pit dimensions
Narrow, deep pits are preferred, as they reduce the need to move carcasses once they are in the pit. It is essential for carcasses to be covered by at least 2 m of soil to ground level.
- Depth: 4 m recommended (this allows 2 m for carcasses, plus a minimum 2 m of soil fill).
- Width: 3 m preferred maximum, or 'one blade width'.
- Length: Depends on number, size, condition and wool length of carcasses to be buried (see calculation of pit length below). As a guide, allow 1 m3 (one cubic metre) for each nine mature shorn Merino sheep in store condition, or 1 m3 per three head of mature cattle in store condition.
Calculating the pit length required
- To calculate the number of carcasses (in sheep equivalents) per metre length of the pit, multiply the width of the pit (in metres) by the depth of carcasses (in metres), and then multiply by 9. The carcass depth is pit depth less 2 m for cover fill.
- Divide the number of carcasses (sheep equivalents) by this number to get the required length of the pit in metres.
For burial of carcasses, one head of cattle is equivalent to 3–4 sheep.
Example
To bury 500 sheep in a pit 3 m wide and 4 m deep:
Carcass depth = 4 – 2 = 2 m
No. of carcasses per metre length of pit = 3 × 2 × 9 = 54
Therefore, length of pit required = 500 ÷ 54 = 9.3 m
Safety to humans and the humane disposal of stock are the overriding considerations.
Either a captive bolt pistol or a rifle can be used for destroying stock. Owners of captive bolt pistols and rifles must comply with the Firearms Act 1996 (NSW) and Firearms (General) Regulation 1997.
In order to kill stock, the respiratory and cardiac centres of the brain, near the junction with the spinal cord, must be destroyed (see Figure 2).
Figure 2. To kill stock efficiently and humanely, aim the shot so that the part of the brain near its junction with the spinal cord is destroyed.
Captive bolt pistols
Captive bolt pistols are safe for the operator but are heavy to handle and, being single shot, are slow to operate. The bolt may require regular cleaning to prevent jamming, especially with sheep if wool is long.
Two operators using two pistols is the best arrangement. One operator does the killing while the other reloads the second pistol.
The captive bolt pistol must be held firmly in contact with the head.
After the animal is dropped, it must be bled by cutting the throat, even if it appears to be already dead (the captive bolt pistol only stuns the animal).
Don't
- Don't try to use on animals which are not immobilised.
- Don't use a cartridge strength which is not powerful enough. Check the manufacturer's instructions.
Do
- Always cut the throat after shooting, because animals are only stunned, not killed.
- Only use in the forehead position, except in sheep where it is more effective at the back of the head.
Rifles
For sheep, 0.22 rifles are often used, but for cattle the minimum is a 0.22 magnum. Rifles above 0.44 magnum should not be used. Low-power hollow point bullets are recommended, but for bulls and older cattle, hard-point or jacketed ammunition may be necessary. Because of the large numbers of sheep which may be involved, self-loading 0.22 rifles may make the job faster, but safety must be a major consideration. Self-loading rifles may not be available, as they require a special licensing arrangement approved by the police.
Rifles will need regular cleaning, and breakages may occur. In addition to adequate supplies of ammunition, spare rifles should be available. One rifle and operator per 1000 sheep or 300 cattle is usually adequate.
Operator safety must be foremost in mind at all times, and everyone other than the person using the rifle should be well clear of the killing pens.
When working in a race, start from the rear and work towards the front. In pens, start close to the pit and work away from the pit.
A moveable panel can be used to keep stock tightly packed together.
The rifle is not held in contact with the animal's head.
Don't
- Don't shoot unless the background is clear.
- Don't shoot over long distances.
- Don't shoot into mobs of animals.
- Don't place the muzzle of the rifle directly against the animal's head.
- Don't shoot in a location where a missed shot might result in a bullet ricocheting off a hard surface near the animal.
- Don't use a weapon that is not powerful enough—check that the calibre and ammunition are suitable for shooting the class of livestock concerned.
Do
- Always shoot animals in the correct place in the head.
- When the animal is facing you, aim at a point where two imaginary lines drawn from each ear to the opposite eye meet on the forehead (Figure 3). Point the gun barrel parallel to the animal's neck.
Figure 3
- When the animal is side-on, aim halfway between the eye and the ear (Figure 4).
Figure 4
Figure 5
Humane destruction of sheep
There are two sites for aiming with pistol or rifle—the back of the head or the front of the head. The back of the head is the preferred site for sheep, as head movement is minimal.
With hornless sheep the captive bolt pistol can be placed on the top of the upper forehead, aimed for the gullet, or just behind the poll and aimed towards the animal's muzzle (see Figure 6(a)).
For horned sheep, the top of the head may not be a suitable position, so use the position just behind the poll and aim towards the animal's muzzle (see Figure 6(b)). Alternatively, when using a rifle, aim at a point in the middle of the face just above the level of the eyes, and shoot towards the spine (see Figure 6(c)).
Figure 6. Recommended position and direction of fire for destroying:
(a) hornless sheep with a captive bolt pistol or rifle
(b) horned sheep with a captive bolt pistol or rifle
(c) horned sheep with a rifle
Humane destruction of cattle
Captive bolt pistols are suitable only for small numbers of cattle that can be adequately restrained.
There are two methods of shooting cattle: the temporal method and the frontal method.
Temporal method
The temporal method is only suitable for rifles. The animal is shot from the side so that the bullet enters the skull midway between the eye and the base of the ear. The bullet should be directed horizontally (see point 'a' in Figure 7).
Frontal method
The rifle is directed at the point of the intersection of lines taken from the base of each horn (or equivalent position in polled animals) to the opposite eye, aiming at the spine (see point 'b' in Figure 7 at right). For bulls or older animals the bullet should enter about 1 cm to the left or right of this point.
Note: Small calves may be shot just behind the nuchal crest (poll) in the mid-line, aiming directly at the muzzle (see point 'c' in Figure 7). Alternatively, a captive bolt pistol may be used.
Figure 7. Recommended position and direction of fire for destroying cattle
Humane destruction of other stock
For advice on the humane destruction of other stock, contact the District Veterinarian at your local Rural Lands Protection Board (RLPB).
Cutting the throat (bleeding out)
Don't
- Don't cut the throat of an animal unless it has been stunned first. Because of the complex blood supply to the brain, animals can remain conscious for up to 5 minutes after the throat is cut.
- Don't delay between stunning and bleeding out, or the animal may regain consciousness, and hence pain perception, before consciousness is lost due to the blood loss.
- Don't use anything but a very sharp knife with a reasonable blade length.
Do
- Always cut down deep to the level of the bones of the neck. All blood vessels in the neck must be cut for quick bleeding, but the spinal cord should not be severed or snapped.
- Stand behind the animal. Grasp the chin and pull the head back towards you. Cut from ear to ear behind the jawbone. Other methods may be used if the operator is experienced.
Judging when an animal is dead
Even after an animal has been stunned or shot, it may paddle its legs, gasp or groan, but still be unconscious—this is all reflex action. However, if the animal raises its head from the ground, as if attempting to rise, it is a fairly reliable sign that it is still conscious. A less reliable sign is blinking of the eyelids when a fingertip is placed on the eyeball.
When an animal is dead:
- the heart stops—feel for this on the left-hand side behind the elbow (note that the heart may take several minutes to cease beating);
- the gums and tongue become bluish-grey;
- the eye appears glazed and the pupil expands.
Always check for these signs and do not assume that an animal is dead just because it is not moving or apparently not breathing.
Any unconscious animals (animals which still show signs of life) must be bled out.
A considerable amount of gas is produced during carcass decomposition. If this gas is trapped inside the carcass, the soil covering the burial pit will be pushed upwards, sometimes allowing fluids and carcasses to 'leak' from the top of the pit.
Slashing of carcasses, while not essential for sheep, may reduce the amount of rising that will occur. Cattle carcasses should always be slashed.
To be effective, a large slash is required. Insert a knife in the left flank between the last rib and the hip to penetrate the rumen, and slash downwards.
When slaughter is completed, all the soil should be replaced to cover the carcasses, forming a mound. This will minimise rising and allow for an eventual return to a more level site.
For further information, contact the District Veterinarian at your local RLPB.
This Agnote is based on material originally written by L. C. Pryde, Former Senior Field Veterinary Officer with NSW Agriculture.
The contribution by John Bowler is gratefully acknowledged.
The information contained in this web page is based on knowledge and understanding at the time of writing (23 December 1999). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of New South Wales Department of Agriculture or the user's independent adviser.
ISSN 1034-6848
© NSW Agriculture 2002
|
No comments:
Post a Comment