1. Field of the Invention
The present invention relates to mastitis detection and to related apparatus, methods and procedures.
The present invention recognises that an advantage is obtained for a farmer where there is the prospect of on-line monitoring of the somatic cell count indicative of mastitis infection in individual animals. Such monitoring either allows a treatment regime to be instituted for the particular animal or animals and/or for the isolation of or recriminations, if appropriate, or in respect of any such affected milk (whether at the milking parlour, farm, factory or elsewhere).
2. Description of the Related Art
Procedures exist whereby a non isolated flow of milk might directly be tested for mastitis. Such procedures have tended to find favour but at the cost of reduced accuracy over isolated milk testing procedures.
Journal of Dairy Research (1998) 65 187–198 “Changes in Electrical Conductivity and Somatic Cell Count Between Milk Fractions From Quarters Subclinically Infected with Particular Mastitis Pathogens” M W Woolford et al. discloses that intramammary infection (which seriously reduces milk yields) is frequently associated with increases in electrical conductivity in milk owing to increased levels of sodium and chloride ions in the milk. The monitoring of electrical conductivity can therefore be a means of automatically tracking udder health. Yet Woolford et al states that factors such as temperature, fat concentration, milk solids, bacterial type, and milk fraction have variously been found to influence the measure of electrical conductivity. It is stated that such factors are important since the increase in electrical conductivity induced by intramammary infection is typically in the range of 15% to 50% only whereas the increase in somatic cell count (SCC) is usually at least 1000% increase. Moreover Woolford et al states there are substantial physiological variations in the normal electrical conductivity levels that preclude comparisons of absolute milk electrical conductivity levels amongst cows for the purposes of identifying infection.
Examples of procedures and related apparatus that have been developed reliant on electrical conductivity to test milk flows include EP0748156 of Gasgoine-Melotte B.V. and PCT/SE97/00671 (published as WO97/40374) of Alfa Laval Agri AB.
The full content of such Woolford et al publication and specifications EP0748156 and WO97/40374 are hereby here included by way of reference.
Gasgoine-Melotte BV in their EPO 748156 comment on two sampling procedures so that still milk can be tested for conductance. They refer inter alia to EP-B-137367.
The Woolford et al publication in addition makes reference to somatic cell count (SCC) as a diagnostic criteria by indicating that, for example, greater than 500,000 cells/ml might be indicative of infection whilst less than 500,000 cells/ml may be indicative of no infection.
TABLE 1(from Woolford et al) Diagnostic criteria for electrical conductivity,within-cow electrical conductivity ratio and somatic cell count usedfor prediction of the infection status of individual quarters.PredictedRequired diagnostic criteriaquarters statusConductivitySomatic cell count, cells/mlInfectedECR > 1.15>500000orEC > 7000 μSUninfectedECR < 1.5<500000where EC is electrical conductivity and ECR is electrical conductivity ratio.
Woolford et al indicates that reliance on somatic cell count (SCC) using a criteria based on 500,000 cells/ml provided greater sensitivity than did the electrical conductivity measures.
Test procedures for mastitis for manually isolated milk are known where the milk that is tested is not subsequently returned to the main volume of the milk.
One type of such isolated milk testing regime is a cow-side gel forming mastitis test procedure. This is typified by the Rapid Mastitis Test (RMT) [or California Mastitis Test (CMT)]. See “Journal of American Veterinary Medical Association, Vol 130, Mar. 1, 1957—No. 5—“Experiments and Observations Leading to Development of the California Mastitis Test” of O. W. Schalm and D. O. Noorlander.
The CMT procedure utilises an anionic surfactant (e.g. a detergent such as, for example, sodium lauryl sulphate commonly marketed at TEEPOL™). The CMT procedure results in a precipitate or gel indicative of the degree of infection (i.e. the SCC).
Australian Journal of Dairy Technology 23, 129 (1968) E A Kernohan has shown that accuracy of somatic cell count (SCC) reliant upon the CMT procedure is dependant on the relative amounts of milk and reagent utilised. For best results preferably a near one to one volume ratio of a suitable reagent to milk is used in equal volumes for best results [for example, 2% w/v sodium laurel sulphate (commonly marketed as TEEPOL™) in water used in equal volume with milk].
Historically the CMT procedure of Schalm and Noorlander was graded on a score outlined below.
This score corresponds to SCC (Milchwissenschaft 19, 65–69 (1964) Halbquantitative Ausarbeitung des Schalmtestes für wissenschaftliche Zwecke of Keirmeier and Keis). The measurement technique used an “eyeball” technique. Therefore some variation exists in interpretation:                (−) negative, remains liquid,        (T) trace, slight precipitate which tends to disappear with more movement, >116 000 cells/ml        (+) weak positive, precipitate but not gel formation, >315 000 cells/ml        (++) distinct positive, thickness immediately with some gel formation, >600 000 cells/ml        (+++) strong positive, distinct gel formation adherence to bottom of paddle and during swirling peaks forms >1 000 000 cells/ml        
The Journal of Milk and Food Technology 27, 271–275 (1964)—“The Wisconsin Mastitis Test—An Indirect Estimation of Leucocytes in Milk” of Thompson and Postle discloses the Wisconsin Mastitis Test (WMT). In the WMT the milk and detergent were mixed in a tube. The tube was then inverted and a small hole in the top ( 3/64 inch diameter) allows the watery part to drain out. The height of the residual was then measured after at least a 1 min inversion This is still in use in some small laboratories today with an active SCC range from 100 000 to 1.2 million cells/ml.
This test was then investigated in the mid 1970s (Milchwissenschaft 27 (2) 1972 “A simple semi-automatic viscosimeter for the estimation of somatic cells in milk”, Whittlestone et al., and Milne et al., 1976) to try and automate the testing for use in the laboratory.
It was found that some ways of measuring the viscosity of the gel destroyed the gel. Ultimately a rolling ball viscometer where the time for a ball to roll through the gel was timed. This eliminated errors due to gel destruction. The active SCC ranges were 250 000–2 million cells/ml (Whittlestone et al.) and 100 000–1.3 million cells/ml (Milne et al.) respectively. This was also undertaken in Germany (Kiermier and Keis 1964).
See also the publications:
                The Australian Journal of Dairy Technology, 21, 138–139, (1966) “An Automatic Viscometer for the Measurement of the California Mastitis Reaction” Whittlestone et al;        Journal of Milk & Food Technology 33, 35–354 (19 . . . ) “A Viscometric Method for the Estimation of Milk Cell court” Whittlestone et al;        Milchwissenschaft 27, (2) 84–86 (1972) “A Simple Semi-automatic Visosimeter for the estimation of somatic cells in Milk” Whittlestone et al and        New Zealand Journal of Dairy Science and Technology, 11, 21–23 (1976) Milne et al        each discuss procedures for measuring the viscosity of the gels of such prior art detergent/milk SCC procedures with a view to determining a viable measurement regime.        
Procedures disclosed include orifice or capillary viscometers (ie; moving gel) as well as falling ball or rolling ball viscometers (ie; stationary gel).
Milne et al standardised a Whittlestone et al type rolling ball viscometer to a tilt angle of 25° in preference to less accurate falling ball viscometers as even very gentle shear forces were found to cause a significant decrease in viscosity. Milne et al found about a 3.5 sec tilt time resulted at that 25° tilt angle when they used a ball of 4.7 mm diameter in a tube of 5.5 mm I.D in a gel made using 2% w/v TEEPOL 610™ (Shell Chemical Company) in water solution as the reagent in volume ratios of 10 ml of the reagent to 5 ml of milk.
The present invention recognises a particular accuracy and convenience is available for any such monitoring regime reliant upon the gelling of a milk sample using an appropriate anionic surfactant and thereafter to test the viscosity by appropriate means to thereby (by reference to some calibration of sample viscosity against the extent of mastitis infection and/or somatic cell count) to provide an indicator representation or record for the particular sample and thus the particular animal.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
It is therefore an object of the present invention to provide apparatus, methods and systems appropriate to the end of enabling on-line monitoring of milk from animals being milked or at least to allow the automatic or semi automatic testing of milk sampled from a milk volume (preferably a milk flow).