Schukken Y H, Grommers F J, Smit J A, Vandegeer D, Brand A
Department of Herd Health and Reproduction, Utrecht, The Netherlands.
J Dairy Sci. 1989 Jul;72(7):1900-6. doi: 10.3168/jds.S0022-0302(89)79309-7.
The objective was to determine the effect of freezing and length of freezing in a commercial freezer on the qualitative results of bacteriologic culturing of milk collected from glands of cows with clinical or subclinical intramammary infections. A total of 182 milk samples from cows with clinical mastitis and 55 milk samples of cows with subclinical mastitis were taken from four problem herds. Samples were split into four equal sub-samples. Three of these were frozen immediately at -20 degrees C and 1 was submitted fresh for bacteriologic analysis. At 4, 8, and 16 wk after collection, samples were thawed and submitted for bacteriologic culturing. Freezing and increased length of storage resulted in 1) a decrease in the number of samples that had cultures of Escherichia coli or Actinomyces pyogenes; and 2) an increase in the number of samples that had cultures of coagulase-negative staphylococci. Freezing had no effect on streptococci and Staphylococcus aureus.
目的是确定在商用冰柜中冷冻及冷冻时长对从患有临床或亚临床乳房内感染的奶牛乳腺采集的牛奶进行细菌培养定性结果的影响。从四个问题牛群中采集了总共182份来自临床型乳腺炎奶牛的牛奶样本和55份来自亚临床型乳腺炎奶牛的牛奶样本。样本被分成四个相等的子样本。其中三个立即在-20℃下冷冻，一个新鲜送去进行细菌学分析。在采集后4周、8周和16周，将样本解冻并送去进行细菌培养。冷冻和储存时间延长导致：1）培养出大肠杆菌或化脓放线菌的样本数量减少；2）培养出凝固酶阴性葡萄球菌的样本数量增加。冷冻对链球菌和金黄色葡萄球菌没有影响。
