great lakes dairy sheep symposium - the Department of Animal ...
great lakes dairy sheep symposium - the Department of Animal ... great lakes dairy sheep symposium - the Department of Animal ...
At each test, the color changes were observed by two different persons in order to detect possible different color perception. The reading with the hand held device was also done twice at a few second intervals to measure the repeatability of the reader. All milk samples used in the trial were sent to a certified laboratory were the somatic cell count in the milk was detected through a Fossomatic 360. The laboratory machine is not especially calibrated for sheep milk. Its accuracy, however, has been tested by comparing the results of a microscopic count (DMSCC) with the electronic count (ESCC). Results of the PortaSCC® were tested against the results from the Fossomatic count. On 8/22/06 each sample of milk was tested twice at a few minute intervals on two different PortaSCC® strips in order to detect the repeatability. At each test we looked at: - the repeatability of the reading of color by two different persons - the accuracy of the color compared to the laboratory results using the same range - the accuracy of the hand held reader compared to the color - the accuracy of the hand held device compared to the laboratory results - the repeatability of the PortaSCC® on the same sample (last test only). The accuracy is simply a percentage of identical results between the Fossomatic and the PortaSCC®. Repeatability is a percentage of identical results for 2 identical milk samples measured by PortaSCC® Results The 18 tests done on 4/17 and the 7 tests done on 4/20 were discarded from the results because the strips used on those dates were past the expiration date. All other results are shown in Table 1. Colors. The colors were generally perceived to be the same by two different people. The percentage of time that the two people had the same reading varied from 75% to 96%. The differences between the two technicians came mostly from hesitation between a no color change and a slight coloration meaning that the accuracy of the test is affected mostly in the low range of SCC up to 200,000. This is quite an acceptable result knowing that an animal with a somatic cell count of 200,000 or less is considered as having a healthy udder (Bergonnier et al., 1997). Correlation between laboratory results and colors. All laboratory results that were less than 200,000 SC were considered 0 and corresponding to a no color change in the PortaSCC® test. The percentage of identical results between the laboratory and the colors shown in the PortaSCC® varies between 81% and 94%. Most of the discrepancies occur in the middle ranges. Therefore, a no color change is definitively an indication of low SCC (less than 200,000) and a deep color change an indication of a high somatic cell count (more than 1 million). However the PortaSCC® does not seem to give quite as accurate results for intermediary ranges (between 200,000 and 1 million), meaning that it is less reliable to distinguish a count of 250,000 from a count of 750,000 just looking at the color on the strip. Also, the repeatability of the color change on the same sample of milk was high at 93%. 94
Correlation between laboratory results and readings from the hand held device. The hand held device is easy to use, small and gives a quick digital reading. After calibrating the device with a blank strip, the strips to be counted are introduced in a slot and read in a few seconds. Theoretically the numbers read (x 10 6 ) should correspond to the level of somatic cells per ml of milk. All laboratories results that were less than 200,000 SC were considered 0. Results show that the accuracy of the hand held device when compared to the Fossomatic results varies from 55% to 73%. The repeatability on the same sample was 66%. A high count detected by the hand held device always corresponded to a high count detected by the Fossomatic counter, but a high count from the Fossomatic did not always correspond to a high count from the hand held reader. Correlation between colors and readings from the hand held device. The correlations varied between 61 and 77% with a repeatability of 61%. Those results have to be expected knowing that there is not a very high correlation between lab results and color in the intermediary ranges of somatic cells level. Conclusion The PortaSCC® appears to be a good tool for the detection of either healthy ewes with no somatic cell or with a very low count (less than 200,000) and for the detection of chronic mastitis ewes with high somatic cell count (more than 1 million). However, for the doubtful ewes with intermediary ranges of somatic cell count (between 200,000 and 1 million) the PortaSCC® as tested in 2006 shows a low accuracy and repeatability. The hand held digital reader does not appear to add any accuracy because of what appears to be erratic readings in the middle range of somatic cell level. In view of our results and of the results of the University of Nevada, PortaCheck has concluded that the enzyme activity of the white blood cell in sheep's milk is about 4 times lower than the enzyme activity of the white blood cell in cow's milk (Personal communication, September 2006). To account for this difference a recalibration of the hand held reader will be necessary for direct reading of sheep milk somatic cells. Litterature cited Bergonier D., M.C. Blanc, B. Fleury, G. Lagriffoul, F. Barillet and X. Berthelot. 1997. Les mammites des ovins et des caprins laitiers: étiologie, épidémiologi, contrôle. 4ème Rencontres autour des Recherches sur les Ruminants. Paris, December 4 and 5, 1997. Publication INRA- Institut de l’élevage. 95
- Page 53 and 54: within-day fluctuation (SCC level a
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Correlation between laboratory results and readings from <strong>the</strong> hand held device. The<br />
hand held device is easy to use, small and gives a quick digital reading. After calibrating <strong>the</strong><br />
device with a blank strip, <strong>the</strong> strips to be counted are introduced in a slot and read in a few<br />
seconds. Theoretically <strong>the</strong> numbers read (x 10 6 ) should correspond to <strong>the</strong> level <strong>of</strong> somatic cells<br />
per ml <strong>of</strong> milk. All laboratories results that were less than 200,000 SC were considered 0. Results<br />
show that <strong>the</strong> accuracy <strong>of</strong> <strong>the</strong> hand held device when compared to <strong>the</strong> Fossomatic results varies<br />
from 55% to 73%. The repeatability on <strong>the</strong> same sample was 66%. A high count detected by <strong>the</strong><br />
hand held device always corresponded to a high count detected by <strong>the</strong> Fossomatic counter, but a<br />
high count from <strong>the</strong> Fossomatic did not always correspond to a high count from <strong>the</strong> hand held<br />
reader.<br />
Correlation between colors and readings from <strong>the</strong> hand held device. The correlations<br />
varied between 61 and 77% with a repeatability <strong>of</strong> 61%. Those results have to be expected<br />
knowing that <strong>the</strong>re is not a very high correlation between lab results and color in <strong>the</strong><br />
intermediary ranges <strong>of</strong> somatic cells level.<br />
Conclusion<br />
The PortaSCC® appears to be a good tool for <strong>the</strong> detection <strong>of</strong> ei<strong>the</strong>r healthy ewes with<br />
no somatic cell or with a very low count (less than 200,000) and for <strong>the</strong> detection <strong>of</strong> chronic<br />
mastitis ewes with high somatic cell count (more than 1 million). However, for <strong>the</strong> doubtful ewes<br />
with intermediary ranges <strong>of</strong> somatic cell count (between 200,000 and 1 million) <strong>the</strong> PortaSCC®<br />
as tested in 2006 shows a low accuracy and repeatability. The hand held digital reader does not<br />
appear to add any accuracy because <strong>of</strong> what appears to be erratic readings in <strong>the</strong> middle range <strong>of</strong><br />
somatic cell level.<br />
In view <strong>of</strong> our results and <strong>of</strong> <strong>the</strong> results <strong>of</strong> <strong>the</strong> University <strong>of</strong> Nevada, PortaCheck has<br />
concluded that <strong>the</strong> enzyme activity <strong>of</strong> <strong>the</strong> white blood cell in <strong>sheep</strong>'s milk is about 4 times lower<br />
than <strong>the</strong> enzyme activity <strong>of</strong> <strong>the</strong> white blood cell in cow's milk (Personal communication,<br />
September 2006). To account for this difference a recalibration <strong>of</strong> <strong>the</strong> hand held reader will be<br />
necessary for direct reading <strong>of</strong> <strong>sheep</strong> milk somatic cells.<br />
Litterature cited<br />
Bergonier D., M.C. Blanc, B. Fleury, G. Lagriffoul, F. Barillet and X. Ber<strong>the</strong>lot. 1997. Les<br />
mammites des ovins et des caprins laitiers: étiologie, épidémiologi, contrôle. 4ème<br />
Rencontres autour des Recherches sur les Ruminants. Paris, December 4 and 5, 1997.<br />
Publication INRA- Institut de l’élevage.<br />
95
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