Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland.
School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
J Anim Sci. 2018 Jun 4;96(6):2099-2112. doi: 10.1093/jas/sky108.
It is anticipated that in the future, livestock will be exposed to a greater risk of infection from parasitic diseases. Therefore, future breeding strategies for livestock, which are generally long-term strategies for change, should target animals adaptable to environments with a high parasitic load. Covariance components were estimated in the present study for a selection of dairy and beef performance traits over herd-years differing in Fasciola hepatica load using random regression sire models. Herd-year prevalence of F. hepatica was determined by using F. hepatica-damaged liver phenotypes which were recorded in abattoirs nationally. The data analyzed consisted up to 83,821 lactation records from dairy cows for a range of milk production and fertility traits, as well as 105,054 young animals with carcass-related information obtained at slaughter. Reaction norms for individual sires were derived from the random regression coefficients. The heritability and additive genetic standard deviations for all traits analyzed remained relatively constant as herd-year F. hepatica prevalence gradient increased up to a prevalence level of 0.7; although there was a large increase in heritability and additive genetic standard deviation for milk and fertility traits in the observed F. hepatica prevalence levels >0.7, only 5% of the data existed in herd-year prevalence levels >0.7. Very little rescaling, therefore, exists across differing herd-year F. hepatica prevalence levels. Within-trait genetic correlations among the performance traits across different herd-year F. hepatica prevalence levels were less than unity for all traits. Nevertheless, within-trait genetic correlations for milk production and carcass traits were all >0.8 for F. hepatica prevalence levels between 0.2 and 0.8. The lowest estimate of within-trait genetic correlations for the different fertility traits ranged from -0.03 (SE = 1.09) in age of first calving to 0.54 (SE = 0.22) for calving to first service interval. Therefore, there was reranking of sires for fertility traits across different F. hepatica prevalence levels. In conclusion, there was little or no genetic variability in sensitivity to F. hepatica prevalence levels among cattle for milk production and carcass traits. But, some genetic variability in sensitivity among dairy cows did exist for fertility traits measured across herds differing in F. hepatica prevalence.
预计未来家畜将面临更大的寄生虫病感染风险。因此，家畜的未来繁殖策略通常是长期的改变策略，应针对能够适应高寄生虫负荷环境的动物。本研究使用随机回归种公牛模型，针对不同肝片吸虫负荷的畜群-年份估计了一组奶牛和肉牛生产性能性状的协方差分量。通过在全国屠宰场记录的肝片吸虫损伤肝脏表型来确定畜群-年份肝片吸虫的流行率。分析的数据包括高达 83821 头奶牛的泌乳记录，涵盖了一系列产奶和繁殖性状，以及 105054 头在屠宰时获得与胴体相关信息的年轻动物。个体公牛的反应规范是从随机回归系数中得出的。所有分析性状的遗传力和加性遗传标准差随着畜群-年份肝片吸虫流行率梯度的增加保持相对稳定，直到流行率达到 0.7；尽管在观察到的肝片吸虫流行率水平>0.7 中，产奶和繁殖性状的遗传力和加性遗传标准差有很大增加，但仅存在 5%的数据存在于畜群-年份流行率水平>0.7。因此，在不同的畜群-年份肝片吸虫流行率水平之间几乎没有重新调整。在不同畜群-年份肝片吸虫流行率水平之间，所有性状的性状内遗传相关性都小于 1。然而，在肝片吸虫流行率为 0.2 至 0.8 之间时，产奶和胴体性状的性状内遗传相关性均>0.8。不同繁殖性状的性状内遗传相关性的最低估计值范围从首次配种年龄的-0.03（SE=1.09）到首次配种至第一次配种间隔的 0.54（SE=0.22）。因此，在不同的肝片吸虫流行率水平下，对繁殖性状的公牛进行了重新排序。总之，在产奶和胴体性状方面，牛对肝片吸虫流行率水平的敏感性几乎没有或没有遗传变异。但是，在不同肝片吸虫流行率的畜群中测量的繁殖性状确实存在一些对敏感性的遗传变异。
