Barkema H W, Van der Schans J, Schukken Y H, De Gee A L, Lam T J, Benedictus G
Animal Health Service, Drachten, The Netherlands.
J Dairy Sci. 1997 Feb;80(2):422-6. doi: 10.3168/jds.S0022-0302(97)75953-8.
The objective of this study was to determine the effect of freezing and the duration of freezing on somatic cell count (SCC) in milk samples from quarters with no signs of clinical mastitis. Effect was determined by a fluoro-opto-electronic cell counter. Samples were frozen in a commercial freezer at approximately -20 degrees C. The milk samples were thawed at 1, 2, 3, 4, 7, 14, or 28 d. Another batch of samples was frozen 1 d, thawed, frozen again for 1 d, and then thawed. The SCC was determined on the fresh samples and after any one of the freezing periods. On average, the SCC were lower after all freezing periods than they were before freezing. However, the difference in SCC before and after freezing was small and relatively constant on the natural logarithm scale. The decrease in SCC was larger with longer freezing periods. When SCC thresholds of 200,000, 250,000, and 500,000 cells/ml were used to predict infection, freezing appeared to have little impact on the sensitivity and specificity of diagnostic parameters. Therefore, SCC, as determined by a fluoro-opto-electronic cell counter, determined for frozen quarter milk samples can be used in mastitis control and research programs.
本研究的目的是确定冷冻及冷冻持续时间对无临床乳腺炎迹象的乳腺牛奶样本中体细胞计数（SCC）的影响。通过荧光光电细胞计数器测定影响。样本在商用冷冻机中于约-20℃冷冻。牛奶样本在1、2、3、4、7、14或28天解冻。另一批样本冷冻1天，解冻，再冷冻1天，然后解冻。在新鲜样本以及任何一个冷冻期后测定SCC。平均而言，所有冷冻期后的SCC均低于冷冻前。然而，冷冻前后SCC的差异较小，且在自然对数尺度上相对恒定。冷冻持续时间越长，SCC的降低幅度越大。当使用200,000、250,000和500,000个细胞/毫升的SCC阈值来预测感染时，冷冻似乎对诊断参数的敏感性和特异性影响很小。因此，通过荧光光电细胞计数器测定的冷冻乳腺牛奶样本的SCC可用于乳腺炎控制和研究项目。
