中文摘要：

为了筛选敏感的奶牛隐性乳房炎早期诊断指标，选择220头荷斯坦泌乳奶牛，分别采集乳汁进行体细胞计数和乳酸脱氢酶（LDH）活性测定。结果显示，隐性乳房炎奶牛乳汁中LDH活性显著高于健康奶牛（P〈0．05），乳汁体细胞数（SCC）与LDH活性呈正相关（r^2=0．93）。选择LDH活性〉100IU／L作为隐性乳房炎的判定阂值，诊断的敏感性为70％，特异性为82．3％，Jouden指数为0．52。结果提示，LDH可作为奶牛隐性乳房炎早期诊断指标。

英文摘要：

In order to screen an sensitive indicator in the earlier diagnosis of subclinical mastitis, the milk samples were collected respectively from a total of 220 lactating Holstein cows in the same dairy farm. Somatic eelI（SCC） was counted and lactate dehydrogenase（LDH） activity was determined in the milk. The results showed that compared to the healthy cows, LDH activity in the milk of subclinical mastitis cows increased signifieantly（P〈0.05）. There was a positive correlation between SCC and LDH activity（r^2 =0.93）. The LDH activity〉 100 IU/L as the threshold to diagnose of subclinical mastitis,its diagnosing sensitivity, specificity and Jouden index were 70 %, 82.3% and 0.52, respectively. These results suggested that LDH could be used as an indicator for early diagnosis of subclinical mastitis of cows.