On-farm death (OFD) of a dairy cow is always a financial loss for a farmer, and potentially a welfare issue that has to be addressed within the dairy industry. The aim of this study was to explore the associations between OFD of dairy cows, housing, and herd management in freestall barns. To achieve the goal, we followed 10,837 cows calving in 2011 in 82 herds. Data were gathered with observations and a structured interview during farm visits and from a national dairy herd improvement database. The hazard of OFD was modeled with a shared frailty survival model, with SAS 9.3 PHREG procedure (SAS Institute Inc., Cary, NC). The study population was 58% Ayrshire and 42% Holstein cows. The median herd size and mean milk yield in the study herds were 116 cows and 9,151 kg of milk per cow per year. The overall probability of OFD was 6.0%; 1.8% of the cows died unassisted and 4.2% were euthanized. Variation in OFD percentage between individual herds was large, from 0 to 16%, accounting for 0 to 58% of all removals in the herds. Keeping close-up dry cows in an own group was associated with higher hazard of OFD [hazard ratio (HR) = 1.37] compared with keeping them in the same pen with far-off dry cows. Higher hazard on OFD was observed when barns had only one kind of calving pens; single (HR = 2.09) or group pens (HR = 1.72), compared with having both of those types. The hazard of OFD was lower if the whole herd was housed in barns or pens that had only 1 type of feed barrier at the feed bunk, namely post-and-rail (HR = 0.51) or a type with barriers between the cow's heads (HR = 0.49), compared with having 2 types. Lower OFD hazard was observed with wider than 340 cm of walking alley next to the feeding table (HR = 0.75), and with housing a whole herd in pens with only 1 type of walking alley surface, specifically slatted (HR = 0.53) or solid (HR = 0.48), compared with having both types. The hazard of OFD was higher with stalls wider than 120 cm (HR = 1.38) compared with narrower stalls. The hazard of OFD was also associated with breed, parity, and calving season. This study identified many factors that contribute to the incidence of OFD of dairy cows. The solutions for reducing on-farm mortality include housing, management, and breeding choices that are most probably herd specific.

奶牛的农场死亡（OFD）始终是农民的经济损失，并且可能是奶业必须解决的福利问题。本研究的目的是探讨速冻谷仓中奶牛的OFD，住房和畜群管理之间的关系。为了实现这一目标，我们在2011年对82头牛的10837头产犊进行了跟踪。在农场访问期间，从全国奶牛改良数据库中收集了观察数据和结构化访谈数据。使用共享的脆弱生存模型和SAS 9.3 PHREG程序（北卡罗来纳州卡里的SAS Institute Inc.）对OFD的危害进行建模。研究人口为58％的埃尔郡和42％的荷斯坦奶牛。研究组的中位牛群大小和平均产奶量为每年每头牛116头奶牛和9,151公斤奶。OFD的总概率为6.0％；1。8％的母牛在无助的情况下死亡，而4.2％的动物被安乐死。各个畜群之间的OFD百分比差异很大，从0％到16％，占畜群中所有清除量的0％至58％。与将它们放在远处的干奶牛放在同一个围栏相比，将近距离的干奶牛留在自己的组中与OFD的危险性更高[风险比（HR）= 1.37]。当谷仓只有一种产犊笔时，观察到对OFD的危害更大。单笔（HR = 2.09）或组合笔（HR = 1.72），而同时具有这两种类型。如果将整个牛群放在饲料仓中只有一种类型的饲料屏障（即栏杆和栏杆（HR = 0.51）或在牛的头之间具有屏障的类型）的情况下，OFD的危险性就会降低。 HR = 0.49），相比之下有2种类型。在靠近喂食台的340厘米以上的步行小巷中观察到较低的OFD危害（HR = 0.75），并且将整个牛群放在只用一种类型的步行小巷表面，特别是板条状（HR = 0.53）或坚固的围栏中（HR = 0.48），而同时具有两种类型。与狭窄的档位相比，大于120 cm（HR = 1.38）的档位对OFD的危害更高。OFD的危害还与品种，胎次和产犊季节有关。这项研究确定了许多因素导致奶牛的OFD发生率。降低农场死亡率的解决方案包括住房，管理和育种选择，这些选择很可能是特定于畜群的。与同时拥有这两种类型相比。与狭窄的档位相比，大于120 cm（HR = 1.38）的档位对OFD的危害更高。OFD的危害还与品种，胎次和产犊季节有关。这项研究确定了许多因素导致奶牛的OFD发生率。降低农场死亡率的解决方案包括住房，管理和育种选择，这些选择很可能是特定于畜群的。与同时拥有这两种类型相比。与狭窄的档位相比，大于120 cm（HR = 1.38）的档位对OFD的危害更高。OFD的危害还与品种，胎次和产犊季节有关。这项研究确定了许多因素导致奶牛的OFD发生率。降低农场死亡率的解决方案包括住房，管理和育种选择，这些选择很可能是特定于畜群的。