Measurement of the component parts of milk, and real time knowledge of the results of these measurements, is an important factor in the efficient management of a dairy farm. Knowledge of the levels of almost all of the various component parts of the milk is important for different aspects of the herd management. These components include fat, total protein, casein, lactose, somatic cells, blood, progesterone, amino-acids urea, and nucleic acid. The fat and protein content, for instance, are major factors in determining the price that the farmer will obtain for his milk, because they are important economic indicators of the overall milk quality. Changes in these values can indicate to the farmer an incorrect diet. Thus, changes in the fat content could indicate an imbalance in the forage-to-concentrate ratio in the feed; low total protein level may indicate a dietetic energy deficiency; the somatic cell count and the blood count may be used as diagnostic indicators of a specific clinical state of the cow; and fluctuations in lactose content, which is generally very stable for a cow, can indicate the presence of mastitis.
Several methods are described in the prior art for performing on-line milk analysis, with the object of more efficient milk production and herd management. The use of near infra-red (NIR) spectroscopy for analyzing milk has been known for almost 15 years, and the early methods used laboratory-type NIR spectrometers for analyzing the milk off-line. A number of such instruments are available commercially, but they are expensive, and their use is thus generally limited to centralized laboratories, to which the farmer would send milk samples for testing typically only once a month.
In the article “Near Infra-Red Spectroscopy for Dairy Management: Measurement of Unhomogenized Milk Composition” by R. Tsenkova et al., published in Journal of Dairy Science, Vol. 82, pp. 2344–2351, 1999, there is proposed a method whereby the milk content is spectroscopically analyzed in the NIR range of from 400 nm to 2500 nm. A proposal is made therein to use fiberoptic probes and relatively inexpensive silicon detectors for detecting the radiation within the range 700 nm to 1100 nm, thereby making the method affordable enough to be applied at the milking station for real-time analysis during milking. However, no details are given of an apparatus suitable for performing this analysis using such silicon detectors. Furthermore, although the use of inexpensive detectors is proposed, no mention is made of the sources that could be used with these detectors to provide the NIR illumination.
The article presents an analysis and comparison of the results obtained in the 1100 to 2400 nm spectral range, to those obtained in the 700 to 1100 nm spectral range, where inexpensive silicon detectors can be used. Essentially continuous measurements (every 2 nm) were made across the whole of these spectral ranges. Though not specifically stated in the article, such spectral coverage can generally be obtained from the internal blackbody illuminating source of most NIR spectrometers. The methods described in the Tsenkova et al. article are largely directed at statistical methods of extracting the desired concentration levels from the overall absorption spectra. A commercial software program was used to develop models for determining fat, total protein and lactose content, and calibration of the models was performed using the Partial Least Squares (PLS) regression technique.
Further descriptions of methods of milk analysis using NIR spectroscopy are given in the articles “Fresh raw milk composition analysis by NIR spectroscopy” by Z. Schmilovitch et al, published in Proceedings of the International Symposium on the Prospects for Automatic Milking, Wageningen, Netherlands, EAAP Publication No. 65, pp. 193–198 (1992), and in “Low Cost Near Infra-red Sensor for On-line Milk Composition Measurement” by Z. Schmilovitch et al., published in the Proceedings of the XIV Memorial CIGR World Congress, 2000, Tsukuba, Japan, some of the authors of which are co-applicants for the present invention.
The spectroscopic measurements themselves in the above-mentioned Tsenkova et al article were performed off-line on collected samples, using a commercial NIR spectroscopic milk analyzer, the Milko-Scan, supplied by Foss-Electric A/S, Hillerod, Denmark. The cost of such instruments is such that they are only generally feasibly economical for installation in central laboratories, and not in every cowshed, let alone at every milking station.
There therefore exists an important need for an inexpensive and simple apparatus and method for the on-line qualitative analysis of milk, which will be sufficiently inexpensive that it can be widely used to enable real-time data to be obtained during the milking process, even at each milking station, but without significantly compromising the accuracy of the measurements required for efficient dairy herd management. Furthermore, the apparatus must be capable of performing its analyses on the type of milk flows typically obtained from milking machines. Such flows are highly pulsed in nature, and generally very turbulent, such that a conventional optical sensing path which measures the optical transmission through the flow from side to side of the flow channel is of limited use.
The disclosures of all publications mentioned in this section and in the other sections of the specification, and the disclosures of all documents cited in the above publications, are hereby incorporated by reference, each in its entirety.