EP1119236A1

EP1119236A1 - A method and an apparatus for detecting mastitis

Info

Publication number: EP1119236A1
Application number: EP99945964A
Authority: EP
Inventors: Torben K. Lindholst
Original assignee: Sa Christensen & Co AS
Current assignee: Sa Christensen & Co AS
Priority date: 1998-10-05
Filing date: 1999-10-01
Publication date: 2001-08-01
Also published as: AU5850799A; DK199801255A; WO2000019807A1; DK174163B1; AR020708A1

Abstract

A method of detecting mastitis in cows by means of a mastitis detector of the flow type which includes a measuring unit with a measuring chamber (1, 1') for each cow's teat with inlet and outlet openings (2, 3, 4) allowing passage of milk from the cow's teat, said measuring chamber (1, 1') being provided with a pair of electrodes (5, 6) for measuring the conductivity of the milk flow. According to the invention the conductivity of the milk from one of the cow's teats is compared with the conductivity of the milk from one or more of the remaining cow's teats. When the difference exceeds a predetermined value, an indication is provided and an alarm is optionally activated.

Description

Title: A method and an apparatus for detecting mastitis.

Technical Field.

The invention relates to a method of detecting mastitis in cows by means of a mastitis detector of the flow type which includes a measuring unit with a measuring chamber for each cow's teat with inlet and outlet openings allowing passage of milk from the cow's teat, said measuring chamber being provided with a pair of electrodes for measuring the conductivity of the milk flow.

Background Art

Such a mastitis detector is advantageous in that it can be mounted on a milk hose extending from each cow's teat to the milk collecting centre. As a result the milk can be checked each time the cow is milked. Moreover, the flow detector is suited for mounting in the short milk hose extending between the milk collecting centre and the teat cups. The mounting of a mastitis detector of the flow type in each of the short milk hoses renders it possible to detect very early signs of mastitis, and in addition it is possible to determine the location of origin of the disease in the udder. As a result it is possible to separate the milk from the sick portion of the udder because this milk can be directed into a separate container through a controllable valve arranged in the short milk hose and/or in the milk collecting centre. Thus the milk from the remaining portions of the udder can be collected and processed in the ordinary manner.

It has been proven that a mastitis infection in dairy cattle can be detected on the basis of a changed pattern in the conductivity of the rnilk, because mastitis results in a considerably increased conductivity.

Measurements of the conductivity render it possible to determine whether said conductivity is considerably increased at a specific time. The electric conductivity is for instance measured by means of electrodes, cf. the description of Dutch Patent Application No. 8301231.

Furthermore, SE 508458 discloses a device for measuring the electric conductivity of milk. The milk from each cow's teat flows through a separate chamber in which two electrodes are arranged for measuring the conductivity. The measuring value is transmitted to a particular evaluation unit. No specific type of signal processing has, however, been described.

Moreover GB 2256278 describes an apparatus for detecting the conductivity of milk. The measured conductivity is compared with a pre-set reference value.

This known apparatus is encumbered with the draw-back that it is necessary to subject the measuring results to a considerable signal processing, and in addition this known apparatus is not particularly flexible.

Brief Description of the Invention

The object of the invention is to provide a method of detecting mastitis, and which is far more simple than hitherto known.

A method of the above type is according to the invention characterised in that the conductivity of the milk from one cow's teat is compared with the conductivity of milk from one or more of the remaining cow's teats, and that an alarm is optionally activated in case the difference exceeds a predetermined value. As a result it is not necessary to carry out calculations, but only comparisons with references from a Table, and accordingly nothing but a simple microprocessor is necessary in connection with a small depot. Such a measuring system does not take up much room, and accordingly it is possible to manufacture said measuring system in a very small and handy size. Moreover, it is according to the invention possible to calculate a continuous average of the conductivity measurements. In this manner erroneous values, if any, are of no significant importance.

The invention relates also to an apparatus of the type indicated in the preamble of claim 5, said apparatus being characterised by the subject matter indicated in the characterising clause of the claim.

Brief Description of the Drawings

The invention is explained in greater detail below with reference to the accompanying drawings, in which

Fig . 1 is an outline sectional view of a conventionally known milking unit connected to the udder of a cow, a mastitis detector according to the invention being associated with said milking unit and being connected to a measuring unit mounted in the milking centre by means of an electric wire,

Fig. 2 illustrates a measuring chamber with inlet and outlet openings for the passage of milk from a cow's teat, said measuring chamber being provided with electrodes for measuring the conductivity of the passing milk,

Fig. 3 is a sectional view of the measuring chamber of Fig. 2,

Fig. 4 illustrates how the milk is directed from the four cow's teats to their respective measuring chambers,

Fig. 5 illustrates an example of associated values of the conductivity measured in each measuring chamber, Fig. 6 illustrates a signal graph showing how the measuring signals are handled, and

Fig. 7a-7d show a flow chart of a program for processing the measuring signals.

Best Mode for Carrying Out the Invention

Fig. 1 illustrates a milking unit 20 connected to the udder 21 of a cow.

Fig. 1 is a sectional view showing all the four teat cups 22 connected to their respective inlets 25 of the milking centre 24 through the respective four short milk hoses 23. The four inlets 25 are uniformly arranged at a distance of 90° from the top side of the milking centre.

The milk is collected in an outlet 26 from the bottom of the milking centre and subse- quently transferred to a collecting container not shown through a hose 27.

Fig. 1 shows also the pulsator tubes 28 extending from the pulsator not shown to the individual teat cups 22, as well as a suspension 29 for the milking unit 20.

Finally, Fig. 1 shows a mastitis detector 30 according to the invention. This mastitis detector is connected to a measuring unit 32 through an electric cable 31 with seven conductors in the present embodiment, said measuring unit 32 being mounted in the milking centre 24. The measuring unit 32 comprises four measuring chambers, viz. one chamber below each inlet 25 in such a manner that during the milking these measuring chambers are filled with milk from their respective cow's teat passing said measuring chambers, but only a representative portion thereof. The remaining milk bypasses the measuring chambers and goes directly into the bowl at the bottom of the milking centre, cf. the more detailed explanation below. The measuring chamber 1 , 1 ' shown in Figs. 2 and 3 for a mastitis detector according to the invention is provided with an inlet opening 2 and some outlet openings 3 , 4 for the passage of milk from a cow's teat. The measuring chamber 1 , 1 ' is provided with a pair of electrodes 5, 6 for measuring the conductivity of the passing milk. A too high conductivity indicates an infection in the teat in question or in the associated milk-producing gland in the udder of the cow. It is, of course, desired to detect such an infected state as early as possible. The latter has according to the invention been solved by means of a particular milk collecting housing or milking centre 24, cf. Fig. 1 , in which four separate measuring chambers 1 , 1 ' are provided, viz. one chamber for each teat HB, VB, HF, VF, cf. Fig. 4. As mentioned above, each chamber 1 , 1 ' is provided with two electrodes 5, 6. In addition, a temperature measuring device can be inserted, optionally in connection with one of the electrodes 5, 6. The principle is that the conductivity of the milk from each of the teats HB, VB, HF, VF is measured. An increase, if any, of the conductivity of the milk from one of the teats HB, VB, HF, VF is caused by salts, such as NaCl, being hberated, and a relative deviation from the conductivity of the milk from one cow's teat is an early sign of an infection. An infection can also be detected by way of an increased temperature of the milk in question. The milk collecting housing 24 in Fig. 1 is connected to a junction cable 31 described in connection with Fig. 1 and being provided with seven conductors, a common earth wire, a conductor for each chamber and two conductors for carrying out a measuring of the temperature. The junction cable 31 is as mentioned in connection with Fig. 1 connected to the measuring unit 32. Previously, the measuring signals in question were transmitted to a so-called management system including historical data on each cow. Furthermore, these data were comparable with the remaining activity of the cow. A high activity, viz. the cow is moving much around, is a sign of the cow being in heat. These activities are detected by means of small electromagnetic markers or radio transmitters secured to each cow.

However, a particularly handy measuring device, viz. the mastitis detector 30, has according to the invention been developed, said device being connected to the above cable. The measuring device 30 is a mini version of the above management system. However, it is only adapted to indicate a possible infected stated in one of the teats HB, VB, HF, VF or in the associated gland, cf. Fig. 4 showing the parts in question of the udder. The particular advantage of the mini version is that it is portable and able to indicate very early signs of an infected state. Ordinarily, an infection is not discovered until it is obvious due to an visibly changed milk, which occurs 1 to 3 days and nights after the conductivity has been increased. In addition, the portable measuring device 30 can indicate the teιτnination of the milking. When the cow is subjected to stress, such a state is also reflected by way of changes in the conductivity and the milk producing capacity. The measurements are indicated in form of flashes on the device, the frequency of said flashes representing a measurement of the relative increase of the conductivity. A relative increase of the conductivity by 15 % results in a predetermined flashing frequency, an increase of the conductivity by 25 % a higher flashing frequency and a relative increase of the conductivity by 40% an even higher flashing frequency on a light indicator corresponding to the teat in question. The observed values are always the highest conductivity values, and in order to ensure that said values are obtained, the measuring is performed a predetermined number of times before the maximum value is measured. The measuring of the conductivity is carried out by means of a 50 kHz signal transmitted through a screened cable. A Kalman-filter can optionally be inserted, said filter serving to provide the continuous average.

Thus four measuring chambers 1 , 1 ' are provided for measuring the conductivity of passing milk from each of the four cow's teats HB, VB, HF, VF. Each new measuring of the conductivity is compared with a variable (reference). When a new, mea- sured conductivity presents a higher value than the above variable, viz. the maximum value, another new variable, viz. a maximum value, is calculated in accordance with the following formula

VF_max: = (1-x) ^• VF_max + X ^• VF where 0< x < 1 During a milking it is desired to find the maximum conductivity for each teat. When the four conductivity values have been obtained, a reference is made to a Table containing the above reference values resulting from a measuring on the system by means of reference fluids presenting different conductivities. Then calculations are made on the resulting data. When a conductivity value of for instance 50 (arbitrary units) has been measured, it is desired to know the conductivity values to be applied to the remaining cow's teats in order to activate an alarm. Three alarm levels apply. The first alarm level can optionally be 60, i.e. when a value of 50 has been measured on a teat it is possible to reference the Table and determine that one of the other teats must present a value of 60 in order to activate the alarm. Three Table values have been encoded corresponding to the value 50. The Table values are for instance 60, 65 and 70 corresponding to the various alarm levels. The signals from the other sensors are compared with these values in order to determine whether or not an alarm is to be activated.

The comparison is made in the following manner:

if (HF max > Tab 1[VF max]) then begin

"Alarm level 1 for sensor HF"; if (HF max > Tab 2[ VF max ] ) then begin

"Alarm level 2 for sensor HF" ; if ( HF max > Tab3 [ VF max ] ) then begin "Alarm level 3 for sensor HF" ; end; end; end; if (VB max > Tabl[ VF max ] ) then begin

The comparisons continue so that all the mutual relationships of the sensors are tested.

The latter has furthermore been illustrated by means of a flow chart of the program indicating the comparisons being made, cf. Fig. 7a-d. In connection with this flow chart it is initially examined whether HF max > VF max and to what extent. In the affirmative, an indication thereof is provided together with an indication of the extent thereof. Then it is examined in a similar manner whether

VB max > VF max and whether

HB max > VF max and whether

VF max > HF max and whether

VB max > HF max and whether HB max > HF max and whether

VF max > VB max and whether

HF max > VB max and whether

HB max > VB max and whether

VF max > HB max and whether HF max > HB max and whether

VB max > HB max

Thus while running this program all the conductivity measurements are compared with one another. In other words nothing but a relative measuring is carried out of the conductivity values in question. In case at least one of these conductivity values deviate substantially from at least one of the remaining values an indication thereof is provided. This indication can for instance be provided by means of an indicator where the udder of the cow has been entered, a lamp being provided for each of the cow's teats. Fig. 1 shows the mastitis detector where the lamps for each cow's teat are designated HB, VB, HF and VF like the respective measuring chambers in Fig. 4. The temperature indicator is designated T, a status contact S and a switch on con- stant K.

When one of the cow's teats or the associated gland is infected, it is indicated by a flashing of the lamp corresponding to the cow's teat in question. The more the lamp is flashing the more said conductivity deviates from the remaining conductivities. A particular advantage of such a signal processing is that a considerable data reduction is performed in a simple manner. In addition, such a signal processing can also be used although the cow has only three or two teats. When one or two teats of the cow is/are dry, an indication thereof is provided in form of the conductivity at the lacking cow's teat being zero. Therefore the program initially asks whether VF max > AD min. If not, all the comparisons with VF max are left out and the next program sec- tion is started, cf. Fig. 7b showing the checking whether HF max > AD min. If not all the comparisons with HF max are left out and the next program section is started , cf. Fig. 7c showing the checking whether VB max > AD min. If not all the comparisons with VB max are left out and the next and final program section is started, cf. Fig. 7d showing the checking whether HB max > AD min. If not, all the compari- sons with HB max are left out. In other words, the comparisons with conductivity values are only carried out if it makes sense. The advantage of the latter is that the equipment can also be used in the situation where the cow is dry on one or two teats.

Furthermore a continuous average is calculated in order to take into account possible erroneous values in such a manner that a possible erroneous value does not form a significant part of the calculation. The program does not include a temperature measurement because such a temperature measurement only serves to indicate whether the cow is feverish. Such a measurement is not used for correction. It is only a question of Table references and comparisons with said references. The program is controlled by a microprocessor. The Table values are encoded in an associated ROM. Moreover, a small RAM is associated. As nothing but comparisons and Table references are to be made, i.e. no actual calculations, it is not required to use a particularly powerful computer.

Fig. 6 shows a signal graph illustrating how the measuring signals are handled. The four measuring signals are fed together with a temperature measurement to a measuring circuit 7 (gate circuit), which determines whether or not the signals are to be transferred to a data processing unit 8. This data processing unit 8 is furthermore supplied with the reference values from Table 1 , 2 and 3. The data processing unit 8 transmits a signal to the milking control 9 in order to check whether a milking is running. In the affirmative a signal is transmitted to a measuring control 11 so as to open the gate circuit 7. In addition, a signal is transmitted to the alarm unit 10 which is to check when data are to be erased and another alarm cycle, viz. from cow to cow, is to be started, the old data being erased and a new cycle being started.

Claims

Claims.

1. A method of detecting mastitis in cows by means of a mastitis detector of the flow type which includes a measuring unit with a measuring chamber (1 , 1 ') for each cow's teat with inlet and outlet openings (2, 3, 4) allowing passage of milk from the cow's teat, said measuring chamber (1 , 1 ') being provided with a pair of electrodes (5, 6) for measuring the conductivity of the milk flow, c h a r a c t e r i s e d in that the conductivity of the milk from one cow's teat HB, VB, HF or VF is compared with the conductivity of the milk from one or more of the remaining cow's teats, and that an alarm is optionally activated in case the difference exceeds a predetermined value.

2. A method according to claim 1 , c h a r a c t e r i s e d in that the conductivity of the milk from one cow's teat HF is compared with the conductivity of the milk from one or more of the remaining cow's teats in such a manner that initially some Table values are determined for the conductivity values in question corresponding to the exceedings expressed in percentages necessary for activating the alarm, whereafter said Table values for the conductivity of the milk from the first cow's teat inclusive of said exceedings expressed in percentages are compared with the conductivities of the milk from the remaining cow's teats, and the Table values for the conductivity of the milk from another cow's teat inclusive of said exceedings expressed in percentages are compared with the conductivities of the milk from the remaining cow's teats, and

the Table values for the conductivity of the milk from a third cow's teat inclusive of said exceedings expressed in percentages are compared with the conductivities of the rnilk from the remaining cow's teats, and

the Table values for the conductivity of the milk from a fourth cow's teat inclusive of said exceedings expressed in percentages are compared with the conductivities of the milk from the remaining cow's teats.

3. A method according to claim 1, characterised in that a continuous average is calculated of the conductivity measurements from each cow's teat.

4. A method according to claim 1, characterised in that nothing but compar- isons with the conductivity values exceeding a predetermined minimum value are performed.

5. An apparatus for detecting mastitis by means of a mastitis detector of the flow type, where a measuring chamber (1, 1') is provided for each cow's teat and comprises inlet and outlet openings (2, 3, 4) allowing passage of milk from the cow's teat, said measuring chamber (1, 1') being provided with a pair of electrodes (5, 6) for measuring the conductivity of the milk flow, a signal processing unit furthermore being provided for signal processing the measured conductivity values, c h a r a c t e r i s e d in that the signal processing unit is adapted to compare the conductivity of the milk from one cow's teat with the conductivity of the milk from one or more of the remaining cow's teats and optionally activate an alarm in case the difference exceeds a predetermined value.

6. An apparatus according to claim 5, characterised in that a possible alarm state is indicated on an image of the udder of the cow, a lamp being provided for each cow's teat, said lamp being adapted to flash on and off in case the conductivity of the milk from the cow's teat in question exceeds the conductivity of the milk from at least one of the remaining cow's teats.