Animal Welfare Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4.
Department of Animal Health Behaviour and Welfare, Harper Adams University, Newport, Shropshire, United Kingdom, TF10 8NB.
J Dairy Sci. 2022 Sep;105(9):7728-7737. doi: 10.3168/jds.2021-21536. Epub 2022 Jul 22.
Lameness assessments are commonly conducted at a single point in time, but such assessments are subject to multiple sources of error. We conducted a longitudinal study, assessing the gait of 282 lactating dairy cows weekly during the first 12 wk of lactation, with the aim of assessing how lameness prevalence changed in relation to case definition and assessment frequency. Gait was scored using a 5-point scale where scores of 1 and 2 were considered sound, 3 was clinically lame, and 4 and 5 were severely lame. We created 5 lameness definitions using increasingly stringent thresholds based upon the number of consecutive events of locomotion score ≥3. In LAME1, a cow was considered lame when locomotion score was ≥3 at any scoring event, in LAME2, LAME3, LAME4, and LAME5, a cow was considered lame when locomotion score was 3 or higher during 2, 3, 4, and 5 consecutive scoring events, respectively. We also assessed the effect of assessment frequency on measures of prevalence and incidence using weekly assessment (ASSM1), 1 assessment every 2 wk (ASSM2), 1 assessment every 3 wk (ASSM3), and 1 assessment every 4 wk (ASSM4). Using LAME1, 69.2% of cows were considered lame at some point during the trial, with an average point prevalence of 31.8% (SD: 2.8) and average incidence rate of 10.9 cases/100 cow weeks (SD: 3.7). Lameness prevalence decreased to 28.0% when using LAME5. Survival analysis was used to assess the effects of parity, using these different case definitions. Parity is a known risk for lameness, such that case definitions and prevalence estimates should be stratified by parity to inform management decisions. Using the LAME3 criterion, primiparous cows had the highest chance of reaching 12 wk without a lameness event, and fourth and higher parities had the lowest. Weighted linear and quadratic kappa values were used to assess agreement between different assessment frequencies and lameness definitions; we found substantial to excellent agreement between ASSM1 and ASSM2 using LAME1, LAME2, and LAME3 definitions. Agreement was fair to substantial between ASSM1 and ASSM3 and low to fair between ASSM1 and ASSM4. Likewise, the agreement between LAME1 and LAME2 was fair in primiparous cows, substantial in second and third parity cows, and poor to fair in fourth and greater parity cows. We conclude that lameness prevalence estimates are dependent upon case definition and that the use of more stringent case definitions results in fewer cows classified as lame. These results suggest that routine locomotion assessments be conducted at least every 2 wk, and that cows should be defined as lame on the basis of 2 consecutive assessments.
跛行评估通常在单一时间点进行，但这种评估受到多种来源的误差的影响。我们进行了一项纵向研究，在泌乳的前 12 周内每周对 282 头泌乳奶牛的步态进行评估，目的是评估跛行的流行率如何与病例定义和评估频率相关变化。步态使用 5 分制进行评分，其中 1 分和 2 分被认为是正常的，3 分是临床跛行，4 分和 5 分是严重跛行。我们使用基于连续运动评分≥3 的事件数量的递增严格阈值创建了 5 个跛行定义。在 LAME1 中，当任何评分事件的运动评分≥3 时，奶牛被认为是跛行，在 LAME2、LAME3、LAME4 和 LAME5 中，当连续 2、3、4 和 5 次评分事件中运动评分 3 或更高时，奶牛被认为是跛行。我们还使用每周评估（ASSM1）、每 2 周评估 1 次（ASSM2）、每 3 周评估 1 次（ASSM3）和每 4 周评估 1 次（ASSM4）评估评估频率对流行率和发病率的影响。使用 LAME1，69.2%的奶牛在试验过程中的某个时间点被认为是跛行，平均点流行率为 31.8%（SD：2.8），平均发病率为 10.9 例/100 头奶牛周（SD：3.7）。当使用 LAME5 时，跛行的流行率下降到 28.0%。使用这些不同的病例定义，生存分析被用来评估胎次的影响。胎次是跛行的已知风险因素，因此病例定义和流行率估计应该按胎次分层，以便为管理决策提供信息。使用 LAME3 标准，初产奶牛达到 12 周无跛行事件的可能性最高，第四胎及以上的可能性最低。使用加权线性和二次 kapp 值评估不同评估频率和跛行定义之间的一致性；我们发现，使用 LAME1、LAME2 和 LAME3 定义时，ASSM1 和 ASSM2 之间具有高度到极好的一致性。ASSM1 和 ASSM3 之间的一致性为公平到高度一致，ASSM1 和 ASSM4 之间的一致性为低到公平。同样，在初产奶牛中，LAME1 和 LAME2 之间的一致性为公平，在第二和第三胎奶牛中为高度一致，在第四胎及以上胎次的奶牛中为差到公平。我们得出的结论是，跛行流行率估计取决于病例定义，使用更严格的病例定义会导致更少的奶牛被归类为跛行。这些结果表明，常规运动评估至少应每 2 周进行一次，并且应根据连续两次评估将奶牛定义为跛行。
