Farm managers' decision to cull dairy cows is based on the cows' milk production, history of disorder(s), and reproductive performance, each of which affects dairy cows' lifetime (herd life and productive lifespan). We investigated the relationships among the incidence of clinical mastitis (CM), the reproductive performance, and the culling rate. We also assessed the effects of these relationships on the lifetimes of dairy cows, using the records made before and after the introduction of an automatic milking system (AMS) at Hiroshima University Farm. Milk yield, CM incidence density, and culling rate of dairy cows increased after the AMS introduction. The CM incidence was associated with an elongation of the calving interval in cows with the same parity. CM in the 1st parity might have caused the reductions of the cows' lifetime and their parity at culling. A higher age at first calving (AFC) was associated with an increase in culling rate but did not lead to a significant decrease in lifetime. Investigations of the factors mediating CM in the 1st parity or AFC with CM incidence or culling rate in the later stages might contribute to the control of lifetime of dairy cows.

中文翻译：

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临床乳腺炎发病率、繁殖性能和淘汰率之间的关系对广岛大学农场奶牛寿命的影响

农场经理淘汰奶牛的决定是基于奶牛的产奶量、病史和繁殖性能，每一项都会影响奶牛的寿命（畜群寿命和生产寿命）。我们调查了临床乳腺炎 (CM) 的发病率、繁殖性能和淘汰率之间的关系。我们还使用广岛大学农场引入自动挤奶系统 (AMS) 前后的记录评估了这些关系对奶牛寿命的影响。引入 AMS 后，奶牛的产奶量、CM 发病密度和淘汰率均有所提高。CM 发生率与同胎次奶牛的产犊间隔延长有关。第一胎的 CM 可能导致奶牛的减少 寿命和他们在淘汰时的平等。较高的初产年龄 (AFC) 与淘汰率增加有关，但不会导致寿命显着缩短。研究介导 1 胎 CM 或 AFC 与 CM 发病率或后期淘汰率的因素可能有助于控制奶牛的寿命。