AU729373B2 - Improved immobilisation of animals - Google Patents

Description

47929 GEH:TA P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

to Name of Applicant: STOCKSTILL LIMITED Actual Inventor: LANCELOT HAMILTON LINES Address for Service: COLLISON CO, King William Street, Adelaide, SA, 5000 Invention Title: IMPROVED IMMOBILISATION OF ANIMALS Details of Associated Provisional Applications: PO8510, DATED 8 AUGUST 1997 The following statement is a full description of this invention, including the best method of performing it known to us: 2 This invention relates to the shearing of sheep, and more particularly to the holding or immobilisation of sheep in position during the shearing operation.

While sheep have been shorn manually for centuries, attempts have been made to ease the physical labour required for the manual shearing of sheep.

Various of these have been to hold the sheep in a cradle or the like at a height convenient to the shearer for manual shearing, or to provide a fully automatic or robotic shearing machine.

However with either of these systems, the sheep has to be held in a position without undue movement, and preferably without any movement such as kicking or struggling.

:-.However with the manual sheering of sheep at a convenient height, ie at about waist height, the sheep is held in a cradle and rotated through 3600 so Sothat the shearer can remove the fleece without undue strain on the shearer's Sback. However it is highly desirable if not necessary for the sheep to remain S1 5 motionless during the shearing operation and during the rotation of the sheep through 3600. One way to do this is to immobilise the sheep.

In our earlier patent AU 657127 there is described a method and apparatus for handling animals by which the animal can be immobilised by the application of a pulsed current of low voltage through spaced electrodes to the 20 spinal column, the duration of the pulses being small in relation to the spacing of the pulses. Also there is described that the pulse width can be lie* °varied to achieve the required result which can be pain block with immobilisation. By this method the animal may be immobilised if desired for animal husbandry. The apparatus for carrying out this method is called an immobiliser.

Thus the immobiliser can be used for immobilising sheep during a shearing operation so that the sheep can be shorn at a convenient height to the shearer, say waist height and turned during the shearing operation, either on rollers or on a continuous belt.

However with immobilisation there is the danger that if the immobilising current is not maintained at the correct level, all the muscles are in a state of tetany, and the animal may thus not be able to breathe.

3 However the shearer prefers that the head and neck of a sheep is able to be manipulated while the back legs are desired to be stiff to avoid kicking, thus enabling the shearer to develop long strokes for optimum performance.

Thus it is an object of the invention to provide a method of immobilization of an animal which ensures that the animal being immobilised is able to breathe in a manner which is not detrimental to the animal's health.

A further object of the invention is to provide a method of immobilisation of an animal which permits the animal to periodically inhale and exhale to a degree that the animal is not distressed by taking a breath or partial breath.

Thus there is provided according to the invention a method of immobilising an animal including the steps of applying spaced electrodes in a position of electrical conductivity to the spinal column, preferably in the mouth and adjacent the tail, and supplying a pulsed current to the electrodes, the duration of each pulse being small 15 in relation to the spacing of the pulses, characterised that the pulses at suitable intervals are turned off and then returned to the previous setting, whereby each time the pulses are turned off the period of interruption is sufficiently long that the :o,:.animal is able to take at least a partial breath, and sufficiently short that the immobilisation is virtually continuous.

For convenience through the following description the present invention may be termed "breath-assist" modification of the immobiliser to thus ensure that heavily immobilised sheep do not suffer oxygen deprivation during heavy application of Selectrical immobilisation.

It has been found that if a mouth clip is used instead of a needle, and another S: 25 needle or clamp is inserted under the tail, that the head and neck can be manipulated while the rear legs are immobilised. This is apparently due to the fact that the current flows via the gastric juices plus the foramina to the base of the brain, while the needle or clamp adjacent the tail gives direct muscle tetany to the legs via the spinal column.

Some shearers for optimum performance desire that the animal be much stiffer than desired by other shearers. Likewise there is a variation in the size and condition of a given group of animals. This may effect the safety of the animal and if the shearer does not check the No 1 requirement "Observe that the animal is breathing" may put the animal's safety at risk.

o* 4 Thus the present invention has been developed to ensure that the animal safety is not put at risk by the personal choice of the shearer, the variation in size of the animal, or even the casual approach of the shearer.

The animal is preferably immobilised at a current setting of from 20 to 60 or milli amps depending upon the size and condition of the sheep and the stiffness can be achieved by operating the with of the electrical pulses.

Typical settings would be from 0.5 to 0.8 milli seconds with a stiffness of the animal increasing with greater width pulses plus a suitable current setting.

At suitable intervals the pulses are turned off and the returned to the previous 1 0 setting giving a continuous pulsed effect. Typical settings would be 4 seconds on and 0.1 seconds off. This allows the animal to take at least a partial breath 1: I to take air into the lungs and the costal muscles to expel air.

In order to more fully describe the invention reference is now made to the accompanying Figure 1 which shows a circuit diagram of the immobiliser 1 5 including the feature of the present invention.

The circuit diagram shows a 6v battery 1, the positive of which is connected to a regulated 50 volt DC. inverter 2 to output of which is connected to one terminal 3 of the immobilising output. Also there is connected in circuit a :el precision low voltage reference 4 and a current pulse amplitude control VR2.

A pulse width control oscillator 5 is controlled by VR1, there also being included a current pulse amplitude operational amplifier 6 connected to the "base of a main switching transistor 7 connected to the other terminal 8 of te immobilising output. Also included is a current sensitive resistor CSR and other suitable resistors R1, R2, R3, and R4.

As shown the pulse width control may be a comparator set up as an asymmetrical oscillator, with the repetition rate set by the timing components R1 and Cl, thus giving the operator external control of the pulse width. V2 simply provides the usual external control for initially setting the required pulse amplitude.

There is also shown a further asymmetrical square wave oscillator, where the 'on' time and the 'off' time are controlled by VR3 and VR4 in conjunction with capacitor C2. The output from this oscillator is applied by resistor R5 and the junction of R2 and R3 to the current pulse amplitude oscillator 6 and has the effect of switching off all immobilising pulses for the 'off' time selected and allowing pulses through the 'on' time selected. A switch SW is provided to allow this function to be switched on and off on demand.

VR3 and VR4 allow adjustment of the' on period desired such as between 2 and 8 seconds and between 0.1 and 0.8 seconds 'off'. These ranges may be varied as desired depending upon the particular animal being immobilised. If desired an LED indicator may be provided to show these cycles in operation.

It is believed that the laryngeal muscle in the trachea prevents the diaphragm from drawing in the air while it is the costal muscles which expel the air, and 1 0 the cessation of the pulses permits these muscles to allow the diaphragm to draw in and expel the air from the lungs. At 0.1 seconds 'off' the muscles of the legs still remain still and yet, but the animal is allowed to take in and expel i° air from the lungs.

S. If during the shearing of a sheep, the shearer follows the operators manual for 1 5 immobilisation of the sheep, the sheep is able to breathe and tests have shown that the oxygen saturation levels show only a minimum deviation from the normal levels of oxygen in the system and the animal is extremely safe during the shearing operation. However it is known that some shearers 0. require a sheep to be more strongly immobilised tomake the sheep stiffer in 20 which condition the sheep may not be able to breathe, and it is this circumstance that the breath-assist immobiliser has been developed.

oleo .0 The breathing of the animal has been monitored with a microphone and amplifier, and it is confirmed by a comparison with the periods of the time off, that at least a partial breath is being taken.

Further tests have confirmed that the sheep is obtaining sufficient oxygen during immobilisation whereby the sheep may be immobilised for considerable periods of time without endangering the health of the sheep.

A comparison was made of oxygen saturations on individual sheep at at rest (normal), under severe electrical immobilisation and under severe immobilisation with the breath-assist of the present invention.

Severe immobilisation is the application of an immobilising current greater than recommended, in which condition the sheep may only be able to breathe with difficulty or may not be able to breathe.

6 Ten sheep were selected at random and their natural oxygen saturations were recorded using a human medical device for digital monitoring of oxygen partial pressure (pulse oximeter). The exposed hairless well diffused portion of the sheep's ear was selected as an equivalent site for the attachment of the digital PPO2 monitor.

SHEEP

Immobilised PPO2% NORMAL

PPO

2

(S)

Immobilised 1

C

.r

C

PPO

2

(S)

Breathassist 84 92 78 88 84 88 87 6 It is noted that the level of electrical immobilisation was varied qualitatively to give a quantitative equivalent state of immobilisation, is the immobilising current was varied depending on the size of the sheep.

Thus the average PPO2 change from normal to immobilisation was 18.8% PPO2 less while the increase from immobilisation to immobilisation with 2 5 breath-assist was an increase of 13.6% PPO2 While the test was only conducted on a sample of 10, it is noted that the average decrease in PPO 2 was 3.45% less with the use of breath-assist, and that the maximum decrease of PPO2 with the assistance of breath-assist was In the opinion of a qualified veterinary surgeon a 10% reduction in 3 0 PPO2 from normal oxygen saturation could be sustained by a healthy animal for a considerable period without permanently endangering the health of the sheep.

Thus typical average readings would be:- Normal sheep 88 PPO2 on the meter scale The sheep was then immobilised in accordance with the instruction manual of the immobiliser with a current setting of 50ma and a pulse width setting of 0.6 mSec. The PPO2 readings were between 86-88 showing that the animal was breathing. The breath-assist was switched on and there was minimal effect noted on the oxygen concentration.

1 0 The current setting was then increased to 70ma with a pulse width of 0.6mSec, the oxygen level declined from 88 to 78 to 80. The breath assist was then switched on and the oxygen level rose to 86 with time.

it has been found that even though the sheep is fully severely :•.immobilised by increasing the current setting above the recommended level, 1 5 by the provision of the invention, it assured that the sheep is able to receive sufficient oxygen. While it has not been determined why the cessation of the pulses-for a very short period of time permits the animal to take at least a partial breath, further tests and development work will determine the exact mechanism why it occurs. It has been found that the periodic cessation of the pulses for a short period of time allows the animal to breathe by taking at least a partial breath while still maintaining tetany on the major portions of the sheep, particularly the leg muscles.

While the above has been described in particular relation to sheep, it is considered within the scope of the invention that a similar technique can be applied to other animals, such as during animal husbandry procedures, and it will be realised that variations in the times of 'on' and 'off' will vary from animal to animal and breed and type of animal.

Claims (4)

1. A method of immobilising an animal including the steps of applying spaced electrodes in a position of electrical conductivity to the spinal column, preferably in the mouth and adjacent the tail, and supplying a pulsed current to the electrodes, the duration of each pulse being small in relation to spacing of the pulses, characterised that the pulses at suitable intervals are turned off and then returned to the previous setting, whereby each time the pulses are turned off the period of interruption is sufficiently long that the animal is able to take at least a partial breath, and sufficiently short that the immobilisation is virtually continuous.

2. A method as defined in claim 1 wherein the animal is a sheep and including the steps of switching the pulses off for a period of between 0.1 seconds and 0.8 seconds every 2 to 8 seconds.

3. A method as defined in claim 1 wherein the spacing of the off period is every 4 seconds. ii

4. A method of immobilising an animal substantially as hereinbefore described with reference to the accompanying drawing. Dated this 171 h day of November 2000 ooo 20 STOCKSTILL LIMITED By their Patent Attorneys l iCOLLISON CO :o:dto o. go 5 ot55