Hunter A C, Jeffrey D C
Vet Rec. 1975 May 17;96(20):442-7. doi: 10.1136/vr.96.20.442.
In a two-year study of the incidence of subclinical mastitis in two beef suckler herds over 2400 quarter milk samples from 180 cows were examined. Somatic cell counts and total bacterial counts were carried out and infecting organisms were isolated on sheep blood agar. Results of these tests indicated that: (a) in spite of extremely dirty udders, fewer contaminants were found in the suckler cow milk samples than in a group of over 1700 samples from typical dairy herds; (b) 18 per cent of all quarter milk samples were infected; (c) 67 per cent of all infections were due to staphylococci and 20 per cent to streptococci; (d) 56 per cent of staphylococcal infections were associated with cell counts less than 500,000 per ml compared with 39 per cent of other infections; (e) 70 per cent of samples had somatic cell counts less than 500,000 per ml. (f) 20 per cent of samples had somatic cell counts over 1 million per ml; (g) only 36 per cent of samples with cell counts over 1 million per ml were associated with udder infections; (h) high cell counts and udder infections were more frequent in early than in mid-lactation. Due to a shortage of animals in the late lactation little evidence was available to support the contention that cell counts rise and the numbers of infected quarters increase towards the end of lactation.
在一项为期两年的研究中，对两个肉牛哺乳牛群的亚临床乳腺炎发病率进行了调查，共检测了来自180头奶牛的2400多个乳房四分之一部分的牛奶样本。进行了体细胞计数和总细菌计数，并在绵羊血琼脂上分离出感染病菌。这些检测结果表明：（a）尽管乳房极其脏污，但在哺乳母牛的牛奶样本中发现的污染物比来自典型奶牛群的1700多个样本中的污染物要少；（b）所有乳房四分之一部分的牛奶样本中有18%受到感染；（c）所有感染中有67%是由葡萄球菌引起的，20%是由链球菌引起的；（d）56%的葡萄球菌感染与每毫升低于500,000个细胞的计数相关，而其他感染的这一比例为39%；（e）70%的样本体细胞计数低于每毫升500,000个；（f）20%的样本体细胞计数超过每毫升100万个；（g）每毫升细胞计数超过100万个的样本中只有36%与乳房感染有关；（h）泌乳早期的高细胞计数和乳房感染比泌乳中期更频繁。由于泌乳后期动物数量不足，几乎没有证据支持在泌乳末期细胞计数上升且感染乳房部分数量增加这一观点。
