PDF(Pubmed)
Abstract：
Perinatal mortality (PM) is a common issue on dairy farms, leading to calf losses and increased farming costs. The current knowledge about PM in dairy cattle is, however, limited and previous studies lack comparability. The topic has also primarily been studied in Holstein-Friesian cows and closely related breeds, while other dairy breeds have been largely ignored. Different data collection techniques, definitions of PM, studied variables and statistical approaches further limit the comparability and interpretation of previous studies. This article aims to investigate the factors contributing to PM in two underexplored breeds, Simmental (SIM) and Brown Swiss (BS), while comparing them to German Holstein on German farms, and to employ various modelling techniques to enhance comparability to other studies, and to determine if different statistical methods yield consistent results. A total of 133,942 calving records from 131,657 cows on 721 German farms were analyzed. Amongst these, the proportion of PM (defined as stillbirth or death up to 48 hours of age) was 6.1%. Univariable and multivariable mixed-effects logistic regressions, random forest and multimodel inference via brute-force model selection approaches were used to evaluate risk factors on the individual animal level. Although the balanced random forest did not incorporate the random effect, it yielded results similar to those of the mixed-effect model. The brute-force approach surpassed the widely adopted backwards variable selection method and represented a combination of strengths: it accounted for the random effect similar to mixed-effects regression and generated a variable importance plot similar to random forest. The difficulty of calving, breed and parity of the cow were found to be the most important factors, followed by farm size and season. Additionally, four significant interactions amongst predictors were identified: breed-calving ease, breed-season, parity-season and calving ease-farm size. The combination of factors, such as secondiparous SIM breed on small farms and experiencing easy calving in summer, showed the lowest probability of PM. Conversely, primiparous GH cows on large farms with difficult calving in winter exhibited the highest probability of PM. In order to reduce PM, appropriate management of dystocia, optimal heifer management and a wider use of SIM in dairy production are possible ways forward. It is also important that future studies are conducted to identify farm-specific contributors to higher PM on large farms.
摘要：
围产期死亡率（PM）是奶牛场的常见问题，导致小牛损失和农业成本增加。目前关于奶牛PM的知识是，然而,有限的研究和以往的研究缺乏可比性。该主题还主要在Holstein-Friesian奶牛和密切相关的品种中进行了研究，而其他乳制品品种在很大程度上被忽视了。不同的数据收集技术，PM的定义,研究的变量和统计方法进一步限制了以前研究的可比性和解释。本文旨在调查两个未开发品种中导致PM的因素，西门塔尔（SIM）和布朗瑞士（BS），将它们与德国农场的德国荷斯坦进行比较，并采用各种建模技术来增强与其他研究的可比性，并确定不同的统计方法是否产生一致的结果。分析了721个德国农场的131,657头母牛的133,942个产卵记录。其中,PM(定义为死产或48小时内死亡)的比例为6.1%.单变量和多变量混合效应逻辑回归，随机森林和通过蛮力模型选择方法的多模型推断用于评估个体动物水平的风险因素。虽然平衡随机森林没有纳入随机效应，它产生了类似于混合效应模型的结果。蛮力方法超越了广泛采用的向后变量选择方法，并代表了多种优势：它考虑了类似于混合效应回归的随机效应，并生成了类似于随机森林的可变重要性图。分娩的困难，母牛的品种和产量被认为是最重要的因素，其次是农场的大小和季节。此外,确定了预测因子之间的四个重要相互作用：品种产卵容易，品种季节，平价季节和产卵缓解农场规模。综合因素,例如小农场的次产SIM品种，夏季容易产卵，显示PM的概率最低。相反，在冬季难以分娩的大型农场上，初产GH奶牛表现出最高的PM概率。为了减少PM,难产的适当管理，最佳的小母牛管理和SIM在乳制品生产中的更广泛使用是可能的前进道路。同样重要的是，进行未来的研究，以确定大型农场中特定于农场的高PM贡献者。
