Electrical conductivity device for detecting mastitis in dairy cows

• US 4,771,007 A
• Filed: 04/27/1987
• Issued: 09/13/1988
• Est. Priority Date: 03/18/1982
• Status: Expired due to Term

• Current Assignee: Wesco Incorporated (HF HOLDINGS INC)
• Original Assignee: Wesco Incorporated (HF HOLDINGS INC)
• Inventors: Bersonnet, George B., Tippetts, Earl L.
• Primary Examiner(s): Marcus, Michael S.
• Application Number:
  US07/043,169
• Time in Patent Office: 505 Days
• Field of Search: 422/68, 422/74, 436/22, 436/23, 436/150, 436/151, 204/409, 119/14.01, 119/14.14, 119/14.15, 324/439, 324/442, 324/443, 324/450, 324/60.1 R, 324/60.1 C
• US Class Current: 436/150
• CPC Class Codes: A01J 5/0133 by using electricity, e.g. conductivity or capacitance
• CPC Class Codes: A01J 5/0136 by using milk flow characteristics, e.g. differences between udder quarters or differences with previous milking runs
• CPC Class Codes: G01N 27/06 of a liquid involving electrolysis G01N27/26
• CPC Class Codes: G01N 33/04 Dairy products

Abstract

An electrical conductivity testing device for detecting mastitis in dairy cows includes an inlet for receiving a sample of milk to be tested, a conductivity cell having a milk flow-through testing passage in flow communication with the inlet, and a milk discharge outlet in flow communication with the conductivity cell, so that a milk sample enters the inlet, flows through the conductivity cell, and flows out through the discharge outlet. The flow described may be continuous or may be discontinuous so that the sample is held in the conductivity cell at least during taking of the conductivity measurement. The conductivity cell is arranged so that it is completely filled with milk during the taking of conductivity measurements. Electrical circuitry is provided to produce an electrical signal proportional to the conductivity of the milk in the conductivity cell.

A preferred embodiment of the device takes conductivity measurements, individually and sequentially, of samples of milk from the four quarters of a cow'"'"'s udder and produces electrical signals representing respective individual conductivity measurements on a scale of from 0 to 9 by electrical comparison of such conductivity measurements with a reference value, preferably by means of a bridge amplifier circuit, and exhibits respective digits representative of such measurements, preferably side-by-side, on a readout screen provided as a part of the instrument.

Claims

1. A hand-held, electrical, conductivity testing device for detecting mastitis in dairy cows, comprising reservoir means for receiving spaced, successive samples of milk as squirted directly from a teat of a cow to be tested and of a volume to be at least partially filled by a single squirt of milk;

two lengths of electrically conductive tubing;

a length of electrically non-conductive tubing joining the lengths of electrically conductive tubing to form an electrical conductivity cell wherein the lengths of electrically conductive tubing form the electrodes of the cell;

tubing means in combination with the electrical conductivity cell forming a milk-flow-through testing passage, said electrical conductivity cell being included as an integral part of said passage intermediate its ends, said passage being smaller in cross-section than said reservoir means and connected in fluid-flow communication with said reservoir means to form an inlet to said passage, so that milk will flow from said reservoir means into and through said passage, said passage being configured as a loop having its inlet and an outlet above the conductivity testing cell when the device is held in normal testing position, milk to be tested entering the conductivity cell from said reservoir means and remaining there until forced out by the next sample or until otherwise emptied, the said outlet of said passage being located below the said inlet thereof, so that, when a sample of milk reaches equilibrium in said passage, no milk is present in the reservoir or passage inlet, whereby, when a successive sample of milk is received in said reservoir means, an air bubble will be formed in the upper part of said passage between the sample at equilibrium and the successive sample, and the inside diameter of said testing passage being small enough to be effective to maintain any bubbles of air trapped between successive samples as bubbles between such samples and to maintain such bubbles between said samples as the samples flow through the passage to thereby flush the preceeding sample from the conductivity cell;

milk discharge means connected in fluid-flow communication with the outlet end of said passage to allow the sample to flow from said passage; and

electrical means electrically connected to the respective electrodes of the conductivity cell for generating an electrical signal representative of the conductivity of the sample of milk in the cell at any given time.

2. An electrical conductivity testing device according to claim 1, wherein the device is adapted to sequentially measure the conductivity of samples of milk taken from the four quarters, respectively, of the udder of a dairy cow, and wherein the electrical means for generating an electrical signal representative of the conductivity of the sample includes a readout screen providing for the display of four digits;

electrical means for comparing a value obtained by said conductivity cell from a test sample of milk taken from one of the four quarters of the udder of a dairy cow, with a reference value and for energizing the display on the readout screen of a digit representative of the resulting comparison value; and

switch means for setting said electrical means into respective condition for energizing the display on the readout screen of digits representative of comparison values obtained for respective test samples from the other three quarters of the udder of said dairy cow, while retaining the digit displays already energized.

3. An electrical conductivity testing device in accordance with claim 1, wherein the conductivity cell is removable and may be replaced by a conductivity cell of differing dimensions so as to adjust the device for use with different herd types.

4. An electrical conductivity testing device in accordance with claim 3, wherein the conductivity cell is mounted on a frame and the frame is removable with respect to the device, so that the conductivity cell is replaced by replacing a frame having one conductivity cell mounted thereon with another frame having a different conductivity cell mounted thereon.

5. An electrical conductivity testing device in accordance with claim 1, wherein the electrical means for generating an electrical signal representative of the conductivity of the sample includes a bridge amplifier circuit for sensing electrical impedance deviations of the test sample in the conductivity cell from a reference impedance and for producing resultant electrical signals indicative of the deviation.

6. An electrical conductivity testing device in accordance with claim 5, wherein the electrical means includes means for demodulating and amplifying the resultant electrical signals, an analog to digital converter to which said demodulated and amplified electrical signals are applied, a display readout screen, and a display driver for receiving the output from said converter and providing values representative of said output to be displayed on the readout screen.

7. An electrical conductivity testing device in accordance with claim 5, wherein the bridge amplifier circuit comprises the conductivity cell;

a reference resistor, the conductivity cell and reference resistor being connected in electrical parallel;

means for applying an alternating current voltage to the parallel connection of the conductivity cell and the reference resistor;

a differential operational amplifier, one input of which is electrically connected to the conductivity cell and the other input of which is electrically connected to the reference resistor;

a feedback resistor electrically connected between the output of the differential operational amplifier and the input connected to the conductivity cell; and

a bias resitor electrically connected between a predetermined voltage and the input of the differential operational amplifier connected to the referenced resistor.

8. An electrical conductivity testing device in accordance with claim 7, wherein the feedback resistor and bias resistor both have substantially the same value of resistance.

9. A method of detecting the presence of mastitis in dairy cows comprising the steps of providing an electrical conductivity testing device for detecting mastitis in dairy cows which device includes reservoir means for receiving spaced, successive samples of milk as squirted directly from a teat of a cow to be tested and of a volume to be at least partially filled by a single squirt of milk, two lengths of electrically conductive tubing, a length of electrically non-conductive tubing joining the lengths of electrically conductive tubing to form an electrical conductivity cell wherein the lengths of electrically conductive tubing form the electrodes of the cell, tubing means in combination with the electrical conductivity cell being included as an integral part of said passage intermediate its ends, said passage being smaller in cross-section than said reservoir means and connected in fluid-flow communication with said reservoir means to form an inlet to said passage, so that milk will flow from said reservoir means into and through said passage, said passage being configured as a loop having its inlet and an outlet above the conductivity testing cell when the device is held in normal testing position, milk to be tested entering the conductivity cell from said reservoir means and remaining there until forced out by the next sample or until otherwise emptied, the said outlet of said passage being located below the said inlet thereof, so that, when a sample of milk reaches equilibrium in said passage, no milk is present in the reservoir or passage inlet, whereby, when a successive sample of milk is received in said reservoir means, an air bubble will be formed in the upper part of said passage between the sample at equilibrium and the successive sample, and the inside diameter of said testing passage being small enough to be effective to maintain any bubbles of air trapped between successive samples as bubbles between such samples and to maintain such bubbles between said samples as the samples flow through the passage to thereby flush the preceeding sample from the conductivity cell, milk discharge means connected in fluid-flow communication with the outlet end of said passage to allow the sample to flow from said passage, and electrical means electrically connected to the respective electrodes of the conductivity cell for generating an electrical signal representative of the conductivity of the sample of milk in the cell at any given time;

holding the device under the teat of a diary cow to be tested;

squirting milk from a selected teat into the reservoir of said device;

allowing the milk to flow from the reservoir into the testing passage until the reservoir is empty;

reading the output of the device which serves as an indication of whether mastitis is present; and

repeating the procedure with another sample.

10. A method of detecting the presence of mastitis in dairy cows according to claim 9, wherein the output of the device is displayed as a number and if the number is higher than a known minimum value mastitis is indicated as present.

11. A method of detecting the presence of mastitis in dairy cows according to claim 9, wherein the procedure is repeated sequentially for each of the four quarters of the udder of a single cow and a comparison of the readings is made before moving to the next cow.

12. A method of detecting the presence of mastitis in dairy cows according to claim 11, wherein the output of the device is displayed as a number and if the number is higher than a known minimum value for any of the four quarters or if the difference between the lowest and highest number is greater than a known maximum, mastitis is indicated as present.

13. A method of detecting the presence of mastitis in dairy cows according to claim 9, wherein the electrical conductivity testing device includes means for separately reading the conductivity of four successive samples of milk provided to the device;

wherein the step of repeating the procedure includes repeating the procedure with milk from each of the four quarters of the udder of a single cow sequentially so that the four successive readings produced by the device will represent readings for each of the four quarters of a single cow; and

a comparison of the four readings is made before taking any successive samples.

14. A method of detecting the presence of mastitis in dairy cows according to claim 13, wherein the four readings of the device are displayed as four separate numbers and if a number is higher than a known minimum value for any of the four quarters or if the difference between the lowest and highest number is greater than a known maximum, mastitis is indicated as present.