School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire, LE12 5RD, United Kingdom.
School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire, LE12 5RD, United Kingdom.
J Dairy Sci. 2018 Feb;101(2):1311-1324. doi: 10.3168/jds.2017-13439. Epub 2017 Nov 23.
It has been demonstrated that low body condition and previous occurrence of lameness increase the risk of future lameness in dairy cows. To date the population attributable fraction (PAF), which provides an estimate of the contribution that a risk factor makes toward the total number of disease events in a population, has not been explored for lameness using longitudinal data with repeated measures. Estimation of PAF helps to identify control measures that could lead to the largest improvements on-farm. The aim of this study was to use longitudinal data to evaluate the proportion of lameness that could be avoided in 2 separate herds (2 populations) through (1) reduced recurrence of previous lameness events, (2) and moving body condition score (BCS) into more optimal ranges. Data were obtained from 2 UK dairy herds: herd A, a 200-cow herd with 8 yr of data from a total of 724 cows where lameness events were based on weekly locomotion scores (LS; 1 to 5 scale), and herd B, a 600-cow herd with data recorded over 44 mo from a total of 1,040 cows where treatment of clinical cases was used to identify lameness events. The PAF for categories of BCS were estimated using a closed equation appropriate for multiple exposure categories. Simulation models were used to explore theoretical scenarios to reflect changes in BCS and recurrence of previous lameness events in each herd. For herd A, 21.5% of the total risk periods (cow-weeks) contained a lameness event (LS 3, 4, or 5), 96% of which were repeat events and 19% were recorded with BCS <2 (3 wk previously; 0 to 5 scale). When lameness events were based on 2 consecutive weeks of LS 4 or 5, 4% of risk periods were recorded as lame, of which 89.5% were repeat events. For herd B, 16.3% of the total risk periods (consecutive 30 d) contained a lameness event (72.6% were repeat events) and 20% were recorded with BCS ≤2 (0 to 120 d previously). The median PAF for all previous lameness was between 79 and 83% in the 2 herds. Between 9 and 21% of lameness events could be attributed to previous lameness occurring >16 wk before a risk period. The median PAF estimated for changes in BCS were in the region of 4 to 11%, depending on severity of lameness. Repeated bouts of lameness made a very large contribution to the total number of lameness events. This could either be because certain cows are initially susceptible and remain susceptible, due to the increased risk associated with previous lameness events, or due to interactions with environmental factors. This area requires further research.
已经证明，低体况和先前的跛行增加了奶牛未来跛行的风险。迄今为止，人群归因分数（PAF）尚未使用具有重复测量的纵向数据来评估跛行，该分数提供了风险因素对人群中疾病事件总数的贡献的估计。PAF 的估计有助于确定可以在农场中最大程度提高的控制措施。本研究的目的是使用纵向数据评估通过（1）减少先前跛行事件的复发，（2）将身体状况评分（BCS）移至更理想的范围，在 2 个独立的牛群（2 个群体）中可以避免的跛行比例。数据来自英国的 2 个奶牛场：牛群 A，一个 200 头奶牛的牛群，有 8 年的 724 头奶牛的数据，其中跛行事件基于每周的运动评分（LS；1 至 5 级）；牛群 B，一个 600 头奶牛的牛群，在 44 个月内记录了 1040 头奶牛的数据，其中使用临床病例的治疗来识别跛行事件。使用适用于多个暴露类别的封闭方程来估计 BCS 类别的 PAF。模拟模型用于探索理论情况，以反映每个牛群中 BCS 和先前跛行事件复发的变化。对于牛群 A，总风险期（奶牛周）的 21.5%包含跛行事件（LS 3、4 或 5），其中 96%为重复事件，19%为 BCS<2（3 周前；0 至 5 级）。当跛行事件基于连续 2 周的 LS 4 或 5 时，有 4%的风险期被记录为跛行，其中 89.5%为重复事件。对于牛群 B，总风险期（连续 30 天）的 16.3%包含跛行事件（72.6%为重复事件），其中 20%的 BCS≤2（0 至 120 天前）。在这两个牛群中，所有先前跛行的中位数 PAF 在 79%至 83%之间。在 9%至 21%的跛行事件中，可以归因于风险期前 16 周以上发生的先前跛行。BCS 变化的中位数 PAF 约为 4%至 11%，具体取决于跛行的严重程度。反复发作的跛行对总跛行事件数量有很大贡献。这可能是因为某些奶牛最初易受影响，并且由于与先前的跛行事件相关的风险增加，因此仍然易受影响，或者是由于与环境因素的相互作用。这方面需要进一步研究。
