CA1147827A

CA1147827A - Activity measurement apparatus for animals

Info

Publication number: CA1147827A
Application number: CA000334591A
Authority: CA
Inventors: J. Carl Derksen
Original assignee: Derksen J C
Current assignee: Derksen J C
Priority date: 1979-08-28
Filing date: 1979-08-28
Publication date: 1983-06-07
Also published as: SE8006034L; GB2058359B; NL8004870A; GB2058359A

Abstract

ACTIVITY MEASUREMENT APPARATUS FOR ANIMALS
ABSTRACT OF THE DISCLOSURE
A system for detecting estrus in cows comprising an apparatus for detecting their rate of motor acticity (movement). A transmitter individual to a cow sends a very short burst of energy to a receiver, at a rate depending on the movement rate of the cow, which counts or records the bursts graphically. The bursts are such as to conserve battery power, minimizing servicing thereof, a burst of a predetermined period being transmitted each time a mercury switch attached to the cow is closed. Count rate of as much as 50% increase indicates reliably the presence of estrus, and a count rate significantly lower than normal can indicate the presence of illness.

Description

~1478Z7 01 This invention relates to an apparatus for 02 measuring the motor activity (movement) of animals, and 03 particularly of dairy cows as an indicator of the presence 04 of estrus.
OS To maximize calf production of cows, it is 06 usually desirable to impregnate each cow of a typical herd 07 at about 80 days following calving. To delay later than 80 08 days reduces the production of the herd. It has been -09 estimated that the economic loss to the producer for each day that conception is delayed beyond 80 days after calving 11 is between $1.00 and $1.60 per cow. Clearly, where hundreds 12 of thousands of cows are in production within a given 13 geographic arèa, the economic advantages could be 14 substantial with improved ability to pinpoint the specific time of estrus of each cow, whereupon artificial 16 insemination can be utilized.
17 The period of estrus in cows is normally about 18 seven to ten hours, and due to the short period of estrus, 19 lt has been difficult to discern accurately the period of estrus on a reliable and ongoing basis. Consequently 21 as many as 120 days typically elapse between calving 22 intervals.
23 Methods used at present to detect estrus are by 24 direct observation (for example, observation of frequency of mounting), the detection of temperature change with 26 temperature-sensitive chemicals or the like, or observation 27 by means of closed circuit television. All of these methods 28 require the attendance and observation of an attendent, and 29 placement of mechanical devices adjacent or in contact with the cows.

~478~7 01 It has been discovered that the motor activity of 02 cows increases significantly during the period of estrus.
03 The present invention makes use of this discovery to provide 04 an automatic indication of when a particular cow is in 05 estrus.
06 A loop of rope is place around the head of a cow, 07 and a switch which is sensitive to movement, such as a 08 mercury switch attached to the rope, closes randomly with 09 movement of the cow. Each time the switch is closed, a transmitter operates and the transmitted energy is received 11 at a receiver for recognition.
12 The use of a movement sensor to determine 13 movement of an animal is not new in itself. For instance, 14 in U.S. Patent 3,336,530, a portable radio transmitter is carried by a hunting dog, and a pair of tones which are sent 16 out by the transmitter are received by the hunter carrying a 17 receiver. The frequency of change of tones is heard by the 18 hunter, and when the changes stop, and a single tone is 19 heard, the hunter knows that the dog is "on point".
Further, the receiver can be used to home-in on the 21 transmitter, and thus allow the hunter to discover his prey.
22 In this and other motion sensing systems, there 23 is a particular drawback which forbids its use in a system 24 such as the present invention. The transmitter can only be used for a short period of time since it is constantly on, 26 or is used for a significant long duty cycle, thus draining 27 the battery after a short period of time. Where the system 28 is to be used for days or weeks at a time in the field, the 29 prior art system is clearly unfeasible.
In addition, the prior art system does not ~47827 01 provide for an automatic determination of movement rates.
02 The user must depend on decoding and interpretation of the 03 information by himself.
04 On the other hand, the present invention provides 05 for substantial battery conservation, which allows use of 06 the transmitter in the field for many weeks without the 07 requirement for servicing of the battery. The invention 08 automatically provides a numerical or other display related 09 to movement, giving an indication of the movement rate of a cow, which when compared with the cow's normal rate of 11 movement, provides an indication of estrus beyond a shadow 12 of a doubt.
13 In addition, it has been found by the use of this 14 invention that a slowed rate of movement of a particular cow relative to its normal rate can indicate the presence of 16 disease. The producer can thus provide prompt attention to 17 the cow, possibly avoiding contamination of other cows in 18 the herd.
19 Clearly the use of the present invention affords substantial improvement of herd management, including 21 increasing efficiency of production and reduction of costs.
22 It should be noted that the invention is not 23 restricted to cows, but can be used to detect rates of 24 movement of other animals for the same or other reasons, particularly to domesticated animals.
26 The invention in general is a system for 27 determining the rate of movement of an animal comprising a 28 transmitter for attachment to the animal, a keying circuit 29 for causing the transmitter to transmit short bursts of energy with movement of the animal, a receiver for receiving 1~478Z7 01 the bursts of energy, and means for counting the received 02 bursts of energy, whereby the rate of movement of the animal 03 can be determined.
04 More specifically, the system i5 comprised of a 0~ transmitter for attachment to the animal, and a keying 06 circuit for causing the transmitter to transmit short bursts 07 of energy with movement of the animal, in which each of the 08 short bursts of energy is emitted for a predetermined period 09 of time. Preferably the keying circuit is initiated by operation of a switch, the periods of the short bursts of 11 energy emissions being made unrelated to the time the switch 12 is closed, but related to the preferred time of emission.
13 Since only extremely short bursts of energy are emitted each 14 time a switch is closed, with large periods of time in the gap between bursts, conservation of battery power is 16 achieved sufficient to allow the transmitter to operate in 17 the field for weeks.
18 Since a plurality of transmitters on different 19 cows are intended to be used in an operating system during the same time, the emission frequencies of the various 21 tran mitters should be different. The receiver should thus 22 have different frequency channels with counters associated 23 with each channel. Preferably the receiver is of the 24 scanning type, in a prototype, the receiver scanned each channel once each second. While bursts occurring during the 26 time that the channel is not being scanned are not counted, 27 the total number of bursts counted relative to the total 28 number of bursts counted during periods of non-estrus can be 29 determined, and has been found to be a reliable indicator of estrus and other relevant factors.

~47827 01 Further, it should be noted that the counter can 02 be of an electronic type, which adds a voltage increment to 03 a sum each time a burst is to be counted, or adds the bursts 04 digitally. The apparatus should reset after predetermined C5 periods of time. An overcount or overvoltage detector which 06 operates an alarm can thus provide an indication if the 07 number of bursts counted during a given interval is in 08 excess of a predetermined minimum. This gives the producer 09 an indication that the cow is in estrus.
Of course, the count threshold can be made 11 variable, and can be established for each particular cow 12 (that is, for each channel), after experience as to the 13 normal count rate for each cow. The system can thus 14 automatically provide the producer with an indication that a cow is in estrus, without attendance except to the alarm.
16 He can read the various counts for various channels, and 17 know unerringly which cow is in estrus, and immediately 18 perform the artificial insemination.
19 A better understanding of the invention will be obtained by reference to the detailed description of the 21 invention below, and to the following drawings, in which:
22 Figure 1 is a view of the transmitter as it is to 23 be applied to an animal, 24 Figure 2 is a schematic diagram of the transmitter, 26 Figure 3 is a block diagram of a receiver, and 27 Figure 4 is a schematic diagram of a modification 28 to a receiver.
29 For ease of description, cows will be the animals referred to below, although the invention can be used with a ~1~7~3Z7 01 variety of animals.
02 Turning first to Figure 1, a rope 1 is provided 03 with a loop and clip 2 at its ends for secure joining 04 together, whereby the rope can be looped securely around the 05 neck of a cow.
06 A housing 3 is hung on the rope by any well known 07 means. In a successful prototype, the rope was looped 08 through a pair of holes in the housing. Within the housing 09 the transmitter is fastened. An antenna 4 for the transmitter can be looped through or around the rope 1.
11 Preferably the housing is relatively heavy, in 12 order that it might pull the rope around the neck of the cow 13 so as to hang below, whereby it will be maintained in an 14 approximate constant position, and not ride up the side of the neck of the cow. In this respect the rope 1 should be 16 loosely hung around the neck of the cow.
17 Within the housing 3 a movement sensitive switch 18 is located for keying the transmitter. Preferably the 19 switch is a well known mercury operated switch. In this switch an amount of mercury is disposed within a glass tube 21 in which a pair of contacts is located. When the mercury 22 runs to the side of the tube where the contacts are located, 23 the mercury completes a conductive path, closing an 24 externally connected circuit.
It may be seen that with movement of the cow, the 26 mercury switch repeatedly and randomly will close. The 27 period of the switch being closed will also be sporadic.
28 However the frequency of closure will be found to be related 29 to the movement rate of the animal.
The transmitter is preferred to be keyed only - ~147~327 01 upon the switch becoming closed. In other words when the 02 switch is closed for a long period of time, or with the 03 switch being open circuited, the transmitter should not 04 operate.
OS Figure 2 shows the preferred form of the 06 transmitter. A transmitting circuit 5 of well known form is 07 shown, which includes oscillator transistor 6 and output 08 transistor 7. The output transistor preferably is biased 09 into class C mode of operation, but can be biased with the base of the output transistor connected through a resistor 11 to its emitter. In these cases, and with no D.C. connection 12 from the base to the + pole of the circuit battery and with 13 the absence of an input signal, it is biased into 14 quiescence, and does not draw operating current.
lS The oscillator transistor has its base connected 16 via resistor 8 to the negative power supply terminal, and as 17 such is biased into quiescence. In its idle state, 18 therefore, neither transistor 6 or 7 draws operating 19 current. Of course while NPN transistors are shown, PNP
transistors could be used with an opposite polarity power 21 supply.
22 The base input of transistor 6 is connected 23 through resistor 9 in series with capacitor lO and mercury 24 switch ll to the positive terminal of a battery 12. The battery negative terminal is connected to the aforenoted 26 resistor 8. Further, its positive terminal is connected to 27 the positive supply lead (unreferenced) of the transmitting 28 circuit 5. Capacitor 10 is bypassed by resistor 13.
29 In operation, movement of the cow will close mercury switch ll temporarily. Capacitor lO thus charges ~1~'7827 01 during the closure period, for a period of time dependent on 02 the RC time constant of its capacitance with the resistance 03 of resistor 9. The charging current flows into the base of 04 transistor 6, thus providing bias current for operation.
05 The transistor will oscillate in a well known manner, 06 applying a signal to class C amplifier transistor 7. The 07 signal is amplified and passes to the external antenna 4, 08 whereby radio frequency electromagnetic energy is emitted.
09 Once the capacitor has become charged or nearly charged, the current flow into the base of transistor 6 11 becomes insufficient to sustain oscillation, and the 12 resulting emission of radio frequency energy stops. This 13 will occur notwithstanding that mercury switch 11 remains 14 closed.
It should be noted that resistor 13 should be of 16 large value which provides a current discharge path around 17 capacitor 10, conducting a current level which is 18 insufficient to maintain oscillation of transistor 6.
19 With switch 11 remaining closed, or opening again, capacitor 10 begins slowly discharging through 21 resistor 13. Once it has discharged, either fully or 22 partly, an additional closure of mercury switch 11 will 23 cause capacitor charging current to flow as described above.
24 The energy emission time is a significant portion of the charging period of capacitor 10, but this period is 26 small in comparison to the total elapsed time. In a 27 successful embodiment of the invention, capacitor 10 was 5 28 microfarads and resistor 9 was 15,000 ohms. Resistor 13 was 29 220,000 ohms. This allowed use of a 9 volt battery as battery 12, to power the transmitter.

~4~82~7 01 Transmitting circuit 5 can be of various well 02 known forms, rather than the specific circuit form shown.
03 It is desired, however, that the circuit should be quiescent 04 except when keyed by the circuit including mercury switch 05 ll, capacitor 10 and resistor 9, in order to minimize the 06 use of battery current. The keyinq circuit in Figure 2, of 07 course, not only causes operation of the transmitter, but 08 also establishes the time period of operation thereof.
09 The operation frequency of the transmitter of the noted prototype was 150MHz, unmodulated. It has been found 11 that modulation is not required. Where various transmitters 12 were used for a herd of cows, the frequencies were preferred 13 to be about 90kHz apart.
14 Where a plurality of transmitters are used for monitoring the motor activity of a herd, a number of 16 different types of receivers could be used. Individual 17 receiver channels each tuned to a frequency of a 18 corresponding transmitter can be utilized. The receiver 19 channel can incorporate circuitry for rectifying the burst of radio frequency energy which is received at its 21 frequency, converting it to a pulse, and applying the pulse 22 to a counter. As noted earlier, the counter can be set with 23 an automatic reset at intervals of, for example, 3 hours, 24 and a count in excess of a normal count at the reset time can be connected to an alarm. This form of circuit in each 26 receiver channel will provide the desired result.
27 However, it is preferred that a scanning type of 28 receiver should be used. The receiver used in a prototype 29 was the VHF SCANNING MONITOR model GRl10, available as Heathkit, from the Heath Company, Benton Harbour, Michigan, 32 * Trade Mark 33 _ 9 _ ~478;~7 01 U.S.A. Modifications of this receiver allow it to be used 02 in the present invention.
03 Turning to Figure 3 a general block diagram of 04 the preferred scanning monitor is shown. An antenna 15 is 05 connected to the input of a radio frequency amplifier and 06 mixer circuit 16. The output of the mixer is applied to a 07 filter and intermediate frequency (IF) amplifier, which is 08 connected to a detector and squelch, the latter assemblage 09 being shown generally as block 17. The output of the detector is connected to an audio amplifier 18 which has a 11 speaker 19 connected thereto. Amplifier 18 and speaker 19 12 are not required as part of this invention, but can be used 13 if desired.
14 Alternatively a low power amplifier and a light emitting diode can be used at the output of the squelch, 16 whereby the diode indicates whether the output is at +5 17 volts or zero. The squelch control is turned so that the 18 light operates or turns off upon the reception of a signal.
19 The output of the squelch is connected to a digital scanning and priority circuit 20, (which is disabled 21 so that scanning continues at a regular speed whether or not 22 signals have been received), the output of which is 23 connected to an eight channel oscillator 21. The output of 24 oscillator 21 is connected to amplifier 22, which has its output connected to the mixer of RF amplifier and mixer 16, 26 in order to establish the frequency to be amplified by the 27 IF amplifier.
28 The circuit also includes a display 23 which 29 shows which of the channels is being scanned at a particular instant.

01 m e operation of this circuit is well described 02 on pages 75 and 76 of the Heathkit Assembly Manual, 03 available from the aforenoted Heath Company, and therefore 04 its recitation would be redundant. However a brief ~05 description of the portions important for an understanding 06 of the present invention will be made.
07 In the digital scanning portion of the circuit, a 08 counter 24, referenced as IC lOl in the aforenoted Manual is 09 operated from a scan oscillator circuit, and receives impulses at the rate of approximately l per second from the 11 scan oscillator. In a prototype, counter 24 was changed to 12 count from O to 5 (a count of 6), rather than from O to 7 as 13 in the available scanning monitor to reduce the number of 14 channels. However, if the RF spectrum space is available, it can be retained to count from O to 7.
16 In order to modify it to count from O to 5, 17 counter 24 is connected directly to counter 25, which is 18 described in the noted Manual as IC 105. The circuits 19 IC102, IC103 and IC104 in the kit are deleted.
The output terminals of counter 25 go to low 21 potential level or ground with counting for 1 second, in 22 sequence.
23 Crystals 26A-26F are referenced in the aforenoted 24 Manual as Y100-Y105. It is preferred that the switches SlOlA-S105 connecting the crystals to the outputs of IC105 26 should be bridged or short circuited, or otherwise 27 permanently closed and are therefore shown as directly 28 connected thereto. The inductors 27A-27F, capacitor 28A-28F
29 and resistors 29A-29F are respectively series connected between crystals 26A-26F and the output terminals of counter 01 25. The inductors correspond to inductors LllO-L115, the 02 capacitors 28A-28F correspond to capacitors C151-C155 and 03 resistors 29A-29F correspond to resistors R141, R143, R145, 04 R147, R149 and R152 in the noted Monitor. Diodes 30A-30F
05 are connected between the junctions of capacitors 28A-28F
06 and resistors 29A-29F respectively, and correspond to diodes 07 D101-D106 of the circuit in the Heathkit Monitor. Numerous 08 components which are present in the monitor have not been 09 shown in the present schematic, since their presence would only add needless complexity to the present description.
11 Returning now to the description of operation, 12 the output terminals of counter 25 each go to low level or 13 ground for one second in sequence. This in turn switches 14 individual corresponding crystals into the oscillator circuit of the scanning monitor. In this manner, individual 16 local oscillator frequencies are generated, which are fed to 17 the mixer as noted earlier, to establish the frequency of 18 reception.
19 In the aforenoted scanning monitor, the IF
amplifier contains a noise amplifier, which is normally used 21 to activate the squelch. The presence of noise indicates 22 that no signal is being received. The noise is converted 23 into a +5VDC positive voltage. If a signal is received, 24 there will be no noise and this positive voltage falls to zero. The +5VDC or zero volt squelch output signal is 26 provided at the output of transistor Q205 in the aforenoted 27 assembly manual. This is applied to lead 31, labelled 28 herein "from squelch".
29 In the present invention each of the output leads of counter 25 is connected through a corresponding resistor ~147827 01 32A-32F to the input of a counter operate circuit such as 02 33F. Only one representative counter circuit is shown, 03 although one is connected to each of the resistors 32A-32F.
04 The squelch lead 31 is connected via resistors 05 34A-34F to corresponding leads which are input to the 06 individual counter operate circuits 33A-33F.
07 Each of the counter operate circuits in sequence 08 thus receives a signal which is output from counter 25, each 09 one as well as a signal from the squelch on lead 31. If both the squelch and one of the signals output from counter 11 25 go to low level at the same time, the counter circuit 12 connected to the corresponding counter output lead is 13 activated.
14 Assuming that a particular output lead from counter 25 is activated (goes to low level), the 16 corresponding crystal will be caused to oscillate, 17 generating a signal in the oscillator (in the present case 18 at its third overtone) which is applied to the mixer, 19 resulting in a particular received frequency to be amplified in the intermediate frequency amplifier. Should a signal be 21 received, the voltage level on the squelch lead 31 will go 22 to low level at the same time as the counter output lead, 23 causing operation of the counter operate circuit which is 24 connected to the particular output lead of counter 25 which had gone to low level. An event counter or display 26 connected to the counter operate circuit thus registers a 27 count.
28 On the other hand shou~d only noise be present at 29 the frequency being monitored, the squelch lead 31 will be at high level and the corresponding counter operate circuit 3~147827 01 will not be operated.
02 In the counter operate circuit 33F which is 03 shown, the input lead is connected to the base of a 04 transistor 35, which, being of NPN type, has its emitter 05 connected to ground.
06 The collector of transistor 35 is connected to 07 the base of a second NPN transistor 36, which also has its 08 emitter connected to ground. A biasing resistor 37 connects 09 the collector of transistor 35 and the base of transistor 36 to a source of potential +Va.
11 The collector of transistor 36 is connected to 12 the coil 38 of an electromechanical counter, to the 13 terminals of which a reverse EMF protection diode 42 is 14 connected. The coil 38 is also connected to source of potential +Va.
16 Should it be desired also to operate a pen or 17 other type of recorder, an additional transistor 39 can be 18 connected a~ transistor 36, with its base to the base of 19 transistor 36, and its emitter connected to ground. Its collector is connected through transducer coil 40 to the 21 recorder. The other terminal of the coil 40 is connected to 22 a source of potential +Vb, and a reverse EMF protection 23 diode 41 is connected across the coil.
24 Upon receipt of a low level or ground signal at the base of transistor 35, which can only occur with the 26 simultaneous reception of a low level signal on the squelch 27 lead 31 and an output of counter 25, transistor 35 is caused 28 to conduct, which in turn causes transistor 36 to conduct.
29 With operation of transistor 36, a circuit is provided from potential source +Va, through coil 38 and the collector ~1478Z7 01 emitter circuit of transistor 36 to ground.
02 This causes registration of an additional count 03 on the counter comprising coil 38.
04 With the connection of transistor 39 as shown, 05 transistor 39 will operate with transistor 36, causing 06 operation of coil 40 and registration on the corresponding 07 event recorder.
08 In place of resistors 32A-32F and 34A-34F, two 09 input AND gates can be used.
In place of each of counter operate circuits 11 33A-33F, the clock input of an integrated circuit counter 12 can be used, whereupon the individual counters are caused to 13 count sequentially with the reception of coincident low 14 level pulses on lead 31 with the output leads of counter 25. A long time counter which provides a low level or 16 ground pulse to the reset input of the latter counters 17 provides for resetting of the counter at predetermined 18 intervals. An alarm driver circuit should be connected to a 19 particular count output of each of the latter counters, in order that an alarm should be operated when the number of 21 counts exceeds a predetermined number prior to the timed 22 resetting.
23 Rather than using counters, a graphical recorder 24 can be used in place thereof or in addition thereto, with pen s recording the individual rate of movement of the cows, 26 one per recoder channel. This provides the advantage of a 27 permanent record, of 24 hours per day.
28 It may be seen that with the resetting function 29 described, under ordinary circumstances the count would never reach the predetermined alarm count level. However ~1~7827 01 during the period of estrus of the cow, with the emission of 02 a greater frequency of pulses from the transmitter, the 03 count, prior to reset, would reach the output level which 04 operates the alarm. Hearing of the alarm, allows the 05 producer to initiate artificial insemination of the cow 06 related to the corresponding channel which set off the 07 alarm. Clearly this allows maximum utilization of herd 08 fertility, with substantially increased reliability.
09 It has been determined that the presence of estrus results in an increased count rate of 50% over 11 normal, although it will normally increase during feeding 12 and decrease during sleep. The count has been found to 13 decrease significantly from a particular cow's normal rate 14 if it is sick.
It should be noted that with the preferred 16 scanning circuit which is described, only 1/6 of the energy 17 bursts or pulses emitted by a transmitter on a particular 18 channel are recorded, since the scanner receives a 19 particular channel only 1 second out of 6. However this count has been found to be a reliable sample of the amount 21 of motor activity.
22 It should also be noted that a plurality of 23 receivers and a plurality of transmitters corresponding 24 thereto can be used, for larger herds. In addition, the audio amplifier and speaker can be utilized to provide an 26 audible indication of the motor activity of the herd, a 27 light emitting diode array can also be utilized.
28 It should be understood that the preferred 29 embodiment described above is only illustrative of the principles of the invention. Other embodiments, and ` 3L14~B27 01 modifications of the present circuit may be utilized within 02 the sphere and scope of the invention. All are deemed to be 03 within the present invention as defined in the claims 04 appended hereto.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:

1. A system for determining the rate of movement of an animal comprising:
(a) a transmitter for attachment to said animal, (b) keying means for causing the transmitter to transmit short bursts of energy with movement of said animal, (c) means for receiving said bursts of energy, and (d) means for counting said received bursts of energy, whereby the rate of movement of said animal can be determined.

2. A system as defined in claim 1, in which each of the short bursts of energy is emitted for a predetermined period of time.

3. A system as defined in claim 1, in which the keying means is comprised of switch means randomly operated upon movement of said animal for applying operation current to the transmitter, and means for controlling the time of each burst of energy irrespective of the time that the switch means is closed.

4. A system as defined in claim 1, in which the transmitter is comprised of a radio frequency oscillator having an input for receiving bias current, a capacitor in series with a switch connected between said input and a current source, and resistor means connected in a discharge path to the capacitor, the switch being randomly operated upon movement of said animal, whereby charging current for for said capacitor is applied for a period of time dependent on the capacitance of the capacitor to said input upon closure of the switch, the oscillator thereby being caused to operate during the interval of a significant portion of charging current flow.

5. A system as defined in claim 4, further including a second resistor connected in series with said capacitor for partly controlling charging time of the capacitor, and a transmitter connected to the output of the oscillator, adapted to be quiescent in the absence of oscillation of the oscillator and to transmit a radio frequency signal during oscillation of said oscillator.

6. A system as defined in claim 1, in which the keying means is comprised of switch means randomly closed for indefinite periods of time upon movement of said animal, and means for causing the transmitter to emit a burst of radio frequency energy for a predetermined period of time upon closure of the switch means.

7. A system for determing the rate of movement of an animal comprising:
(a) a transmitter for attachment to said animal, (b) keying means for causing the transmitter to transmit short bursts of energy with movement of said animal, in which each of the short bursts of energy is emitted for a predetermined period of time, (c) means for receiving said bursts of energy, and (d) means for counting said received bursts of energy, whereby the rate of movement of said animal can be determined.

8. A system as defined in claim 7, in which the keying means includes a switch adapted to be randomly closed for indefinite periods with movement of the animal, the switch being connected in a circuit to said transmitter to cause said transmitter to operate, and further including means for causing a burst of radio frequency energy to be emitted each time the switch is closed for a predetermined period which is equal to or shorter than the time period that the switch is closed.

9. A system as defined in claim 8, in which the transmitter includes an oscillator transistor having a bias current input, the output of the oscillator transistor being connected to the input of an output transistor circuit which is biased for class C operation, the oscillator transistor circuit being adapted to be in its quiescent state in the absence of said bias current, a source of current, a capacitor in series with a first resistor connecting the current source to said bias current input, and a second resistor connected in a circuit around the capacitor for discharging the capacitor, the time constant of the capacitor and the first resistor being selected to establish said predetermined period.

10. A system as defined in claim 3, 8 or 9 in which the switch is a mercury switch.

11. A system as defined in claim 3, 8 or 9 in which the switch is fixed to a loop of rope for disposition around the neck of an animal, and a weight attached to said rope for hanging below the neck of the animal and orienting the switch physically in a predetermined position to facilitate random operation with movement of the animal.

12. A system as defined in claim 3, 8 or 9 in which the switch is fixed to a loop of rope for disposition around the neck of an animal, and a weight attached to said rope for hanging below the neck of the animal and orienting the switch physically in a predetermined position to facilitate random operation with movement of the animal, the weight comprising a housing enclosing said transmitter and keying means.

13. A system as defined in claim 1, in which the means for counting includes a circuit tuned to the frequency of the received energy, and for detecting and recording said received burst of energy.

14. A system as defined in claim 1, 4 or 6 in which the means for counting includes a circuit tuned to the frequency of the received energy, means for converting each received energy burst into a signal pulse, and counter means for counting the pulses.

15. A system as defined in claim 1, further including a plurality of transmitters tuned to different frequencies for attachment to individual animals, keying means connected to each of the transmitters for causing each of the transmitters to transmit short bursts of energy with movement of said animals, in which the means for counting includes a plurality of circuits each tuned to different frequencies of energy received from corresponding ones of the transmitters, means for converting bursts of energy received from each of said plurality of circuits into pulses, and counting means connected to said converting means for receiving and counting said pulses, each respective counter counting the pulses related to an individual frequency of a corresponding transmitter.

16. A system as defined in claim 1, in which the means for receiving said energy is comprised of a frequency scanner for scanning a plurality of different frequency channels associated with corresponding ones of a plurality of said transmitters, each transmitter having a keying means, the means for counting being comprised of means for converting the bursts of energy received in each channel to pulses, and counting means for counting the number of pulses received in each channel during the period the associated channel is scanned.

17. A method of determining the presence of estrus in cows comprising:
(a) transmitting a plurality of bursts of energy, the frequency of the bursts being related to the movement rate of the cow, (b) counting a sample of said bursts within a predetermined period, and (c) comparing the total number of the sample with a predetermined number, and establishing the presence of estrus in the event the total number is greater than said predetermined number.

18. A method of determining the presence of sickness in cows comprising:
(a) transmitting a plurality of bursts of energy, the frequency of the bursts being related to the movement rate of the cow, (b) counting a sample of said bursts within a predetermined period, and (c) comparing the total number of the sample with a predetermined number, and establishing the presence of sickness in the event the total number is smaller than said predetermined number over a predetermined period of time.