Department of Animal Sciences, Faculty of Agriculture, Food and Environment, the Hebrew University, Rehovot, Israel.
J Dairy Sci. 2011 Sep;94(9):4538-45. doi: 10.3168/jds.2011-4293.
The aim was to evaluate the effects of mastitis, determined by the pattern and level of somatic cell count (SCC) around first artificial insemination (AI), on conception rate (CR). Data from 287,192 first AI and milk records covering a 7-yr period were obtained from the Israeli Herd Book. Analyses examined the association of probability of conception with SCC elevation relative to timing of AI, using generalized linear mixed models. A SCC threshold of 150,000 cells/mL of milk was set to distinguish between uninfected cows and cows with mastitis. Accordingly, cows with high SCC before and low SCC after AI were designated cured, those with low SCC before and high SCC after AI were designated newly infected, and cows with high SCC before and after AI were designated chronic (likely subclinical) mastitic cows. Compared with uninfected cows, the cured, newly infected, and chronic subgroups showed reduced CR (39.4±0.1, 36.6±0.2, 32.9±0.3, and 31.5±0.2, respectively). In the chronic, subclinical group, probability of conception was lowered by 14.5% in the mild and moderately elevated SCC subgroups and by 20.5% in cows with high SCC elevation compared with the uninfected group (CR of 29.7 vs. 39.4%, respectively). A single high elevation of SCC (>10(6) cells/mL on only 1 milk test day) lowered the probability of conception by 23.6% when it occurred during the 10 d immediately before AI, but not when it occurred earlier. For 30 d after AI, probability of conception was lowered by about 23%, as reflected in a CR of about 27% compared with the uninfected group. Probability of conception was lowered in cows with uterine and foot health problems (33.9%), in multiparous cows (34.1%), and in cows in the summer (29.1%), but no interactions with mastitis were detected. Results indicate that SCC elevation around AI, typical for subclinical mastitis, was associated with a significant reduction in probability of conception, and that even mild SCC elevation reduced CR. Severe elevation of SCC before AI, typical for clinical intramammary infection, reduced the probability of conception.
本研究旨在评估首次人工授精（AI）前后体细胞计数（SCC）水平和模式确定的乳腺炎对受胎率（CR）的影响。该研究数据来自以色列牛群记录，共包括 287192 次首次 AI 和 7 年的牛奶记录。采用广义线性混合模型，分析了相对于 AI 时间，SCC 升高与受孕概率的关系。设定 SCC 阈值为 150000 个/mL 牛奶，以区分未感染牛和乳腺炎牛。根据 SCC 水平，将 AI 前 SCC 高、AI 后 SCC 低的牛指定为治愈牛；AI 前 SCC 低、AI 后 SCC 高的牛指定为新感染牛；AI 前和 AI 后 SCC 均高的牛指定为慢性（可能为亚临床）乳腺炎牛。与未感染牛相比，治愈牛、新感染牛和慢性牛的 CR 分别降低了 39.4±0.1%、36.6±0.2%、32.9±0.3%和 31.5±0.2%。在慢性亚临床组中，SCC 轻度和中度升高亚组的受孕概率分别降低了 14.5%，SCC 显著升高的牛的受孕概率降低了 20.5%，与未感染组相比（CR 分别为 29.7%和 39.4%）。在 AI 前 10 天内仅 1 次 SCC 升高（＞106 个/mL），受孕概率降低了 23.6%，而在更早时间发生时 SCC 升高对受孕概率无影响。在 AI 后 30 天内，受孕概率降低了约 23%，与未感染组相比，CR 约为 27%。子宫和蹄部健康问题（33.9%）、经产牛（34.1%）和夏季（29.1%）的牛受孕概率降低，但未发现与乳腺炎之间存在交互作用。结果表明，AI 前后 SCC 升高（亚临床乳腺炎的典型特征）与受孕概率显著降低有关，即使是轻度 SCC 升高也会降低 CR。AI 前 SCC 严重升高（典型的临床乳腺炎）降低了受孕概率。
