VetEnt Research, 49 Benson Road, Te Awamutu 3800, New Zealand.
College of Veterinary Science, Palmerston North 4474, New Zealand.
Vet J. 2019 Oct;252:105356. doi: 10.1016/j.tvjl.2019.105356. Epub 2019 Aug 16.
Dairy calf mortality is of interest worldwide as animal welfare continues to increase in importance to the consumer. This review summarises overall estimations of perinatal mortality from published literature, then further explores the limitations of each publication as well as its applicability, and challenges faced in use of the generated data for comparisons. The first limitation is the definition of perinatal mortality. There is no agreed definition of the period over which perinatal mortality can occur and, depending on the source, estimates may include late-gestation abortions and deaths up to 48h. In 26 studies identified by the literature search, 11 explicitly mentioned that they excluded abortion, by excluding calvings with too short a gestation length, or in a situation where calves were born in a tight cluster, excluded calvings that were more than 3 weeks prior to the planned start of calving. One study separated out the stillbirth percentage and abortion percentage. One study stated that abortion was included in their perinatal mortality data, and the remaining 13 studies included stillbirth but never mentioned any exclusion criteria for abortion. Seventeen studies measured mortality up to 24h or less, six up to 48h and three had unknown time periods. The second issue is study design. Of the 26 studies, seven were prospective studies and 19 were retrospective analyses. There are clear advantages to prospective studies as protocols can be put in place to maintain data quality. In contrast, ensuring data quality on retrospective studies is more difficult. One clear issue is the inclusion of data from herds with no perinatal mortality information. In a prospective study, herds that are not reporting any mortality can be easily identified and specific checks put in place to ensure recording is accurate; this cannot happen in a retrospective analysis. Thus retrospective studies which include data from herds with no perinatal mortality (especially when herd size is >100) are likely to be underestimating perinatal mortality. Across the studies, the unweighted mean of mortality estimates was 6.2%. However, if the objective is to compare countries, farming management, years or more, results must always be interpreted with caution. The variability in methods of data collection, validation, definition and even just applicability of the studies is large and if comparisons are to be made close examination of the methods of the studies being used as a comparison or benchmark for farms, regions or countries is crucial.
奶牛犊牛死亡率是全球关注的问题，因为动物福利对消费者的重要性不断增加。本综述总结了已发表文献中围产期死亡率的总体估计，然后进一步探讨了每篇出版物的局限性及其适用性，以及在使用生成数据进行比较时面临的挑战。第一个限制因素是围产期死亡率的定义。对于围产期死亡率可能发生的时间段，尚无共识定义，而且根据来源的不同，估计可能包括妊娠后期流产和死亡，最长可达 48 小时。在文献检索中确定的 26 项研究中，有 11 项明确提到，它们通过排除妊娠期过短的产犊或在犊牛紧密聚集的情况下产犊，或在产犊计划开始前超过 3 周产犊的情况，排除了流产。一项研究将死产率和流产率分开。一项研究表示，流产已包含在其围产期死亡率数据中，其余 13 项研究包括死产，但从未提及任何关于流产的排除标准。有 17 项研究测量了 24 小时或更短时间内的死亡率，6 项研究测量了 48 小时内的死亡率，3 项研究的时间未知。第二个问题是研究设计。在这 26 项研究中，有 7 项是前瞻性研究，19 项是回顾性分析。前瞻性研究有明显的优势，因为可以制定方案来保持数据质量。相比之下，确保回顾性研究的数据质量更加困难。一个明显的问题是包含没有围产期死亡率信息的牛群的数据。在前瞻性研究中，可以很容易地识别出没有报告任何死亡率的牛群，并采取具体的检查措施确保记录准确；这在回顾性分析中是不可能的。因此，包括没有围产期死亡率（尤其是当牛群规模大于 100 时）的牛群数据的回顾性研究可能会低估围产期死亡率。在所有研究中，死亡率估计的未加权平均值为 6.2%。然而，如果目的是比较国家、养殖管理、年份等，那么必须谨慎解释结果。数据收集、验证、定义甚至研究适用性的方法差异很大，如果要进行比较，必须仔细检查正在使用的研究方法，将其作为农场、地区或国家的比较或基准。
