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Reliability of Ekomilk instruments

Reliability, best practices, accuracy and repeatability specifications of Ekomilk milk analysis instruments

Overview on studies, laboratory comparisons, papers and articles about the reliability of Ekomilk milk analyzers
 

Accuracy and repeatability specifications

Ekomilk instruments usually have some specifications in the user's manual and / or brochure which indicate the accuracy and / or repeatability of the milk parameter(s) , ingredient(s) or properties measured. On this page we give background to these figures.

About the terms used, if we mention CV, we mean coefficient of variation, also called the relative standard deviation (RSD). It's basically the standard deviation (sigma or s) divided by the average (arithmetic mean) of the results. In other words, it's expressed in percents %.

Ekomilk Horizon Unlimited, Ekomilk Standard, Ekomilk M, Ekomilk Ultra, Ekomilk Bond for fat, protein and total solid content (milk composition):

July 2017: Ekomilk Horizon Unlimited is by far the most accurate and reliable solution for analysing milk composition, thanks to the full calibration options in the Cloud and the sample verification and preparation by the AMPI Sample Feeder. Please find here a small study:

http://animalmonitoring.com/accuracy-results-farm-ekomilk-amp-measurement-somatic-cells-fat-protein-content-cow-milk/

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http://www.ekomilk.eu/content/accuracy-ekomilk-analyzer-instruments-fat-content-total-solids-and-protein-content

Publications of studies with universities are being prepared on cow, goat, buffalo and sheep milk.

 

Ekomilk Horizon Unlimited, Ekomilk Scan and Ekomilk Scan+ for subclinical mastitis detection and mastitis control programs:

For mastitis prevention and mastitis control, the somatic cell count (SCC) is the most common indicator used worldwide since several decades. Most comparisons calculate the accuracy via R² value (the correlation coefficient) and a coefficient of variation (CV) for the actual comparison (sometimes after recalibration), repeatability (via coefficient of variation, CV) and the specificity and sensitivity figures (positive and negative predictive values) of the Ekomilk cell counter in relation to a "Gold standard" method and technology. This so-called Gold standard for somatic cell count in milk from dairy livestock (cow, sheep, goat), is usually based on flow cytometry technology. In order to be valid for comparisons and calibrations, this flow cytometry technology and method has to be used in an official, regularly calibrated laboratory using equipment like Fossomatic, Bentley or other.

The R² value is often calculated for a simple linear regression hence is called a correlation coefficient in this case. In reality, Ekomilk allows more complex calibration curves so the actual accuracy (R² value) of Ekomilk Scan is often higher. The R² value should be calculated for non-linear regressions; the R² value will then be a coefficient of determination instead of a correlation coefficient.

Besides these written studies about the repeatabilty and accuracy of Ekomilk Scan + somatic cell counter, many informal (no publication) lab comparisons, DHI (dairy herd improvement) and milk control comparisons have been performed in Europe, the Amercias, Africa and Asia.

July 2017: Ekomilk Horizon Unlimited is by far the most accurate and reliable solution for measuring the SCC level and milk composition, thanks to the full calibration options in the Cloud and the automated sample verification and sample preparation by the AMPI Sample Feeder. Please find here a small study:

http://animalmonitoring.com/accuracy-results-farm-ekomilk-amp-measurement-somatic-cells-fat-protein-content-cow-milk/

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  • Accuracy R² and repeatability CV, fresh cow milk; Holstein cattle; Belgium / Luxembourg / Bulgaria: This is a small scale study performed on samples analysed between 2011 and 2013 in Belgium, Luxembourg and Bulgaria. The focus in this study is on the repeatability (coefficient of variation, CV) and correlation coefficient (R²) when comparing with official milk quality control laboratories. These official milk quality control laboratories are called "le contrôle laitier" in France and Belgium, Dairy Herd Improvement associations ( DHI and DHIA ) and milk control centers in other countries. For fresh milk from mainly Holstein cows, a correlation coefficient (R²) around 0.95 is found with Ekomilk Scan and Ekomilk Scan+ for the somatic cell count (SCC) results when comparing with the official laboratory milk analysis results.

White paper about accuracy and repeatability report of Ekomilk Scan cell count tester for mastitis control programs

 

  • Accuracy R² and CV, reproducibility CV, repeatability CV, cow milk of different ages; Holstein, Jersey, Crossbreed and Gyr (Gir) cattle; Brazil: This is a large scale study performed in Brazil in 2014 on 4 different cow breeds (Holstein, Jersey, Crossbreed and Gyr or Gir).  The usual Gold standard for somatic cell count in milk from dairy livestock (cow, sheep, goat), is used here: flow cytometry. The focus in this study is on the influence of measurement testing conditions like milk measurement temperature, milk composition and operator (end-user). The repeatability (coefficient of variation, CV), reproducibility (coefficient of variation, CV),  and correlation coefficient (R²) for the different cow (cattle) breeds are calculated. The influence of a common milk sample conservative (Bronopol) is also verified, confirming earlier findings that conservatives should not be added to the milk sample when using Ekomilk analysis equipment. Similarly, the study confirms the influence of conservation time of the milk sample (time between sampling and measurement with Ekomilk), on the Ekomilk result. Finally, the theoretical accuracy after re-calibration is calculated. A correlation coefficient (R²) around 0.95 and a CV of 22% is found with Ekomilk Scan. As in most studies, the flexible nature of Ekomilk thanks to its digital approach is not fully taken into account; Ekomilk allows much more complex calibrations besides a simple linear regression. Also the age and the temperature of the milk is now digitally compensated for with Ekomilk.

Dissertation "EVALUATION OF RESULTS OF SOMATIC CELL COUNTS OBTAINED BY EKOMILK EQUIPMENT AND ITS CORRELATIONS WITH OTHER METHODS OF ANALYSIS".

(currently only in Portuguese)

 

  • Accuracy R² and CV, repeatability CV, Se and Sp, cow quarter milk of different ages; Holstein cattle; Belgium: This is a large scale study performed in Belgium in 2015 on milk measured with Ekomilk Scan between 24 and 96 hours after sampling. While the Gold standard for somatic cell count in milk from dairy livestock (cow, sheep, goat), is here again flow cytometry (Fossomatic 5000), a comparison with the DCC from DeLaval is also included. The study can be found here (there is a summary in English, the details are in French): Memoire_Barbara: Comparaison_de_tests_cellulaires_directs_et_indirects_de_détection_de_la_mammite_bovine.pdf  These study (thesis, memoire) results could be seen as a worst case scenario test: milk was tested up to 96h after sampling from individual Holstein cow quarters while storing the milk at a far-from-ideal 6°C. Ekomilk Scan was not designed for testing such old milk stored at this non-standard temperature (milk tanks are usually around 2°C). The accuracy results, especially the overall correlation coefficient of 0.80 and the high Se and Sp figures around 200 000 cells/ml, are a confirmation that even under such special conditions, Ekomilk Scan is still reliable for mastitis monitoring. 

 

  • Accuracy R² and CV, repeatability CV, cow milk of specific age; Holstein cattle; Switzerland, France, other European countries: This is an ongoing study performed in several EU countries on typical tank milk, comparing with the usual Gold standard for somatic cell count in milk from dairy livestock (cow, sheep, goat): flow cytometry. The first results can be read here. The next (partial) publication is planned for Q4 2016.