WO2002058475A1

WO2002058475A1 - Method of and apparatus for rendering an animal insensible

Info

Publication number: WO2002058475A1
Application number: PCT/GB2002/000210
Authority: WO
Inventors: Mehmet Haluk Anil; Stuart Raymond Butler
Original assignee: The University Of Bristol
Priority date: 2001-01-23
Filing date: 2002-01-18
Publication date: 2002-08-01
Also published as: GB2371203A; GB0101748D0; EP1357797A1

Abstract

A non-invasive method of rendering an animal insensible is provided. At least one coil is brought adjacent an animal"s head and a large rate of change of current is caused to flow therein such that a rapidly changing magnetic flux cuts through the animal"s brain tissue.

Description

METHOD OF AND APPARATUS FOR RENDERING AN ANIMAL INSENSIBLE

The present invention relates to a method of and apparatus for rendering an animal insensible. Such an apparatus may be employed within an abattoir in order to protect animal welfare at the time of slaughter.

Currently used methods of stunning animals prior to slaughter are often not effective. Electric stunning involves applying a clamp to the animal's head and applying the voltage of between 70 and 400 volts at a frequency for 50-1500 Hertz. It will be appreciated that animals do not come with convenient bare conducting patches of skin on their heads, and consequently contact resistance can be significant. The application of the current can result in bruising, broken bones and haemorrhaging. It is also estimated that where this process is used on pigs approximately one in five animals are not rendered unconscious by this procedure. Thus a significant proportion of animals suffer distress during the electrical stunning process.

Typically, poultry are stunned in a water bath in order to improve conduction through the bird. Nevertheless, distress and discomfort still arise during this process. Furthermore significant haemorrhaging can occur following such electrical stunning.

Non-electric stunning methods are also known. Captive bolt stunning is achieved by firing a bolt at high velocity into the head of an animal. The bolt is held within the stunning apparatus and then has a short degree of travel. The bolt makes a hole in the animal's skull. However, a significant proportion of animals will show signs of recovery after this process and consequently it is known to insert a stick (pithing rod) into the animal's head in order to physically damage the brain and brain stem of the animal. It is also possible that the animal may not be stunned due to too low a bolt velocity or incorrect positioning on the animal's head.

Gas stunning is also known and is often applied to pigs and poultry, especially in Scandinavian countries. Gas stunning is typically either performed in a carbon dioxide atmosphere or an Argon atmosphere. In an Argon atmosphere the animals tend to pass out peacefully, but then undergo a lot of struggling which causes bruising and damage to the meat. A carbon dioxide atmosphere results in animals passing out in a state of distress but overall the amount of struggling that they undergo is less and consequently the meat is less damaged.

Other stunning methods, such as microwave irradiation of the brain have also been disclosed but none of these methods offers a reliable pain free way of killing or stunning an animal.

According to the present invention, there is provided a method of rendering an animal insensible, comprising the steps of bringing the animal's head into the operating region of a magnetic field generator, and operating the generator to induce a changing magnetic flux, the changing magnetic flux interacting with the brain of the animal so as to induce sufficient current flow therein to render the animal insensible.

It is thus possible to provide a non-contact method of rendering an animal insensible.

It should be noted that 'insensible' does not necessarily mean unconscious. The magnetic field may be applied to specific regions of the animal's cortex such that its perception of pain becomes blocked. However, if the animal is rendered incapable of feeling pain, and of being congniscent of its surroundings then the distinction between insensible and unconscious becomes irrelevant. An advantageous way of rendering an animal insensible is to induce a seizure such as an epileptic seizure within the animal.

According to a further aspect of the present invention there is provided a method of creating a seizure and rendering an animal insensible, the method comprising the steps of bringing the animal's head into the operating region of a magnetic field generator, and operating the generator to induce a changing magnetic flux, the changing magnetic flux interacting with the brain of the animal so as to induce sufficient current flow therein to inhibit movement of the animal.

It is thus possible to immobilise and render an animal insensible, and preferably unconcious such that it does not struggle, and thereby damage its meat, during a subsequent slaughtering step. Preferably the magnetic field is generated by the flow of electricity within one or more windings. In order to obtain the high rates of change of flux to generate significant reduced current within an animal's head, it is highly desirable to keep the inductance of the coil low. Typically the coil inductance will be less than 20 micro Henrys.

In order to increase flux density, a variety of coils may be provided, each with its respective power supply such that the coils can be operated in such a way that their fields combine constructively.

Advantageously the coils are driven with monophasic pulse. Such a pulse can be obtained by discharging a capacitor into the coil via a thyristor.

In use, the coils typically generate a magnetic field of at least one Tesla or so in the plane of the coil. This magnetic field typically has duration of several milliseconds. It can therefore be appreciated that the rate of change of magnetic flux is very high. For large animals larger field strengths and shorter durations, thereby giving rise to greater rates of change of flux may be desirable.

However, it is possible that the use of large electromagnets or rare earth permanent magnets will be able to induce fields of the required intensity. These magnets, or more likely keepers and/or magnetic shields may be moved with respect to an animal's head in order to induce changing flux within the animal. Such devices may be used in combination with magnetic coils and associated power supplies.

Advantageously a plurality of stimulations are applied to the animal's head with a peak flux density occurring within a region of the animal's brain. Multiple stimulations may prolong the recovery time that it would take for an animal to regain consciousness or feeling, or to recover from a seizure.

In general, it is required that an animal within a slaughterhouse should be rendered insensible or in seizure for at least 20 seconds. This is because, once an animal has been rendered insensible, it will then have a major artery or vein cut in order that the animal can be exsanguinated. Typically this is done by cutting the blood vessels in the neck. After 15 to 20 seconds an animal has normally lost a sufficient amount of blood that it would become unconscious and/or will remain unconscious.

The present invention will further be described, by way of example, with reference to the accompanying figures, in which:

Figure 1 - Schematically illustrates a 'stun' station within an abattoir; and

Figure 2 - Schematically illustrates a circuit for driving the excitation coils.

Figure 1 schematically illustrates a station within an abattoir where an animal is rendered insensible. The animal, generally indicated 1, is conveyed on a conveying system, generally indicated 2, towards one or more magnetic coils located within a supporting structure, generally indicated 4. The or each coil is connected to a power supply unit 6. The coils are arranged such that, in use, they can be placed adjacent an animal's skull 8. In order to achieve this one or more coils may be held on moveable clamps in order that the coils can be brought into near or touching contact with an animal.

Figure 2 schematically illustrates the power supply and coil in great detail. A high voltage supply 10, which may either work in a continuous or pumped mode is arranged to store charge on a high voltage capacitor 12. A rectifier 14 is provided between the supply 10 and the capacitor 12. The capacitor 12 is connected in series with a thyristor 13 which itself is connected in series with the coil 14. The coil 14 is connected in parallel with a flyback diode 16. The coil 14 comprises a few turns of wire, which gives rise to an inductor, having the value L. The capacitor has a capacitance C.

In use, the capacitor is charged up to a high voltage, in the range of 1,000 to 3,000 volts by the high voltage supply 10. Once the animal is conveyed to the correct position with respect to the coil 14, the thyristor is activated. This, in effect, connects the capacitor to the coil, allowing the energy of the capacitor to be discharged into the coil. The thyristor is a mono-directional device, and consequently it acts to block repeated oscillation of current between the capacitor and the coil. The flyback diode 16 serves to provide a current path around the loop comprising of the flyback diode of 16 and the coil 14, thereby protecting the circuit from high voltage transients once the thyristor 13 becomes non-conductive. It is desirable to obtain a good magnetic field strength at the animal's head. Analysis of the performance of coils is within the skill of the engineer. However, it is well known that the magnetic field strength in the "X" direction of the coil is given by the following formulae e_xμ₀Ia² To = 2(α2_+Λ;2) 1.5

Where: B is the magnetic field in Tesla; e_x is a unit vector in the direction of x increasing on the axis of the coil; μ₀ is the permeability of free space;

/is current; a is the radius of the coil; and x is the distance along the direction e?.

For a coil of n turns, the above equation is multiplied by n.

Thus, in general terms, to obtain a magnetic field the current should be high, the number of turns of the coil should be high, and the radius of the coil should be small. However, these actions lead to the coil having a increased inductance L. In order to obtain good rates of change of field, then the rate of change of current in the coil needs to be high.

Ignoring internal resistance of the coil in the capacitor, the rate of change of current di/dt is given by dL - Σ dt L

Thus it is desirable to keep the inductance of the coil as small as possible.

The situation is further complicated by the fact that, in order to store a reasonable amount of energy to discharge into the coil, the storage capacitance C has to be fairly large and typically has a value in the region of 1 milli Farad. This necessitates the use of electrolytic capacitors, which themselves can exhibit parasitic inductance and resistance tending to degrade system performance. In order to provide multiple stimulations, banks of power supplies may be provided, thereby reducing the load and dissipation requirements on any one single supply. Similarly, because the peak currents in the coil can be high, rising to approximately 8,000 amps after typically 150 to 200 microseconds from excitation, then resistive heating within the coil can be significant and consequently the coils may need to be cooled.

Multiple coil configurations may advantageously be used. The provision of coils in a generally side by side arrangement reduces the fall off of field strength, thereby allowing the field to penetrate deeper within the animal's brain. Spaced apart the coil configurations, similar to helmholtz coils may also give further penetration into the target animal.

Although monophasic operation has been described thus far, multiphasic operation, that is where the coil starts to go into resonance can also be used to stimulate the brain and induce currents therein sufficient to disrupt normal function.

It is thus possible to provide a non-invasive, and non-contact, method of rendering an animal insensible, or immobile. The animal is typically a pig, cow, deer or sheep, although this list is not to be considered exhaustive.

Claims

1. A method of rendering an animal (1) insensible, comprising the steps of bringing an animal's head (8) into the operating region of a magnetic field generator (4,6), and operating the generator to induce a changing magnetic flux, the changing magnetic flux interacting with the brain of the animal so as to induce sufficient current flow therein to render the animal insensible.

2. A method as claimed in claim 1, in which the animal is killed whilst insensible.

3. A method as claimed in claim 2, in which the animal is killed by exsanguination.

4. A method of rendering an animal immobile, comprising the steps of bringing an animal's head (8) into the operating region of a magnetic field generator (4,6), and operating the magnetic field generator (4,6) to induce a changing magnetic flux, the changing magnetic flux interacting with the brain of the animal so as to induce sufficient current flow therein to render the animal (1) immobile.

5. A method as claimed in claim 4, in which the animal (1) is killed whilst immobile.

6. A method as claimed in claim 5, in which the animal is killed by exanguination.

7. A method as claimed in claim 4, in which the changing magnetic flux induces a seizure in the animal (1).

8. An apparatus for rendering an animal insensible, the apparatus comprising a magnetic field generator (4) for generating a changing magnetic field so as to induce a sufficiently large changing magnetic flux within the brain of an animal to render the animal insensible or immobile.

9. An apparatus as claimed in claim 8, in which the magnetic field is generated by electric current flowing in at least one wire.

10. An apparatus as claimed in claim 9, in which the current is monophasic.

11. An apparatus as claimed in claim 9, in which the current is biphasic.

12. An apparatus as claimed in claim 9, in which the current is polyphasic.

13. An apparatus as claimed in claim 8, in which the magnetic field is generated by a permanent magnet or an electromagnet.

14. An apparatus as claimed in any of the claims 8 to 13 where the peak field strength exceeds 1 Tesla.

15. An apparatus as claimed in claim 8 where the rate of change of field intensity exceeds 300 Tesla per second.

16. An apparatus as claimed in claim 8 where the rate of change of field intensity exceeds 300,000 Tesla per second.