Department of Population Medicine, University of Guelph, ON, Canada.
J Dairy Sci. 2012 Dec;95(12):7372-6. doi: 10.3168/jds.2012-5846. Epub 2012 Oct 11.
Lameness is one of the most important welfare and economic problems in modern dairy herds. In addition to environmental factors, lameness is affected by genetics and thus, long-term improvement of lameness can be accomplished through genetic selection. The objective of the study was to estimate the genetic parameters of a validated gait score and specific gait attributes for Holstein cows from a university dairy research herd. Two hundred thirty-three cows were gait scored multiple times over time (n=1,664 records) in different experiments using a 1-to-5 numerical rating system (NRS). One hundred seventy-two cows (n=657 records) also had 6 gait attributes scored using a 100-unit continuous visual analog scale (back arch, head bob, tracking up, joint flexion, asymmetric gait, and reluctance to bear weight). Single-trait linear animal models were used to estimate the heritability of NRS and each gait attribute, whereas a multivariate linear animal model was used to estimate genetic correlations between traits. The NRS and the gait attributes deteriorated with parity, and the scores for NRS, back arch, joint flexion, and asymmetry of the steps increased rapidly in early lactation. The heritability estimate (±SE) for NRS was 0.09±0.09. Four of the gait attributes (reluctance to bear weight, head bob, tracking up, and asymmetry of the steps) had higher heritability than NRS, ranging from 0.11±0.13 to 0.42±0.15, whereas back arch showed no genetic variation. However, the small sample of animals resulted in large standard error of the estimates. The genetic correlations between NRS and the gait attributes were >0.70, whereas the genetic correlations among the different gait attributes ranged from 0.14 to 0.92. In conclusion, NRS and most gait attributes showed genetic variation, indicating the opportunity to improve gait through genetic selection. Some specific gait attributes were more heritable than NRS and were genetically correlated with NRS. Further research with a larger population is needed to assess whether specific gait attributes would be suitable candidate traits to consider in genetic evaluations in the future.
跛行是现代奶牛场最重要的福利和经济问题之一。除了环境因素外，跛行还受遗传因素的影响，因此，通过遗传选择可以长期改善跛行。本研究的目的是估计验证后的荷斯坦奶牛步态评分和特定步态属性的遗传参数，该数据来自一个大学奶牛研究牧场。233 头奶牛在不同的实验中多次进行步态评分（n=1664 条记录），使用 1 到 5 的数字评分系统（NRS）。172 头奶牛（n=657 条记录）还使用 100 个单位连续视觉模拟量表（背拱、头部晃动、跟踪、关节弯曲、步态不对称和承重犹豫）对 6 个步态属性进行评分。使用单性状线性动物模型估计 NRS 和每个步态属性的遗传力，而使用多变量线性动物模型估计性状间的遗传相关性。NRS 和步态属性随胎次而恶化，NRS、背拱、关节弯曲和步态不对称评分在泌乳早期迅速增加。NRS 的遗传力估计值（±SE）为 0.09±0.09。4 个步态属性（承重犹豫、头部晃动、跟踪和步态不对称）的遗传力高于 NRS，范围从 0.11±0.13 到 0.42±0.15，而背拱没有遗传变异。然而，由于动物样本较小，导致估计的标准误差较大。NRS 与步态属性之间的遗传相关性大于 0.70，而不同步态属性之间的遗传相关性范围从 0.14 到 0.92。总之，NRS 和大多数步态属性都表现出遗传变异，表明有机会通过遗传选择来改善步态。一些特定的步态属性比 NRS 更具遗传性，并且与 NRS 具有遗传相关性。需要进一步进行更大规模的研究，以评估特定的步态属性是否适合作为未来遗传评估中的候选性状。
