Genetic parameters for resistance to nematode infections in Texel lambs and their utility in breeding programmes
Genetic parameters for resistance to nematode infections in Texel lambs and their utility in breeding programmes
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DOI：
10.1017/s1357729800053972
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发表时间：
2004-04-01
期刊：
影响因子：
--
通讯作者：
Stear, MJ
中科院分区：
文献类型：
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作者：
Bishop, SC;Jackson, F;Stear, MJ
本文论述了商品特克赛尔羔羊对胃肠道线虫感染的寄主抗性遗传，以及对寄生虫的抗性在育种计划中的作用。在两个特克塞尔绵羊群中，在四年的时间里，每只羔羊在断奶后最多三次测量自然寄生虫攻击后的粪卵计数，这两个农场分别测量了1385只和287只羔羊。每只羔羊都有活体重、断奶时超声测量的脂肪和肌肉深度，以及深厚的家系。卵数在所有情况下都是中等到高度可遗传的，其中线虫的卵数比粗线虫的卵数更具遗传性。粗线虫和线虫产卵量的加权平均遗传力分别为0.26和0.38。在同一种类的寄生虫中，随着时间的推移，遗传相关性是正的和强烈的，但略低于统一性，同时测量的斯特里尔线虫和线虫卵计数之间的相关性也是如此。表现性状与粗线虫卵数之间的遗传相关通常是有利的(即负的)，但较弱，而与线虫卵数的遗传相关通常是中性或略为正的。虽然对线虫的抗性不一定包括在育种目标中，但结果表明，线虫的卵数可以作为强力型卵数的额外遗传指标，而几乎没有额外的成本。将减少虫卵数量的流行病学后果纳入提高寄生虫抵抗力的益处，这表明在英国条件下，将活重和对数转化卵数并重的选择目标将是提高生长速度和减少寄生虫幼虫挑战的有力手段。
This paper addresses the inheritance of host resistance to gastro-intestinal nematode parasite infections in commercial Texel lambs, and the role of resistance to parasites in breeding programmes. In two flocks of Texel sheep, faecal egg counts following natural parasite challenge were measured on up to three occasions post weaning per lamb over a 4-year period, with 1385 and 287 lambs measured on the two farms. Live weight, and ultrasonically measured fat and muscle depth at weaning were available for each lamb, as were deep pedigrees. Egg counts were moderately to strongly heritable on all occasions, with Nematodirus egg counts more heritable than the Strongyle egg counts. Weighted average heritabilities for Strongyle and Nematodirus egg counts were 0.26 and 0.38, respectively. Within the same category of parasite, genetic correlations across time were positive and strong but somewhat less than unity, as were the correlations between Strongyle and Nematodirus egg counts measured at the same time. Genetic correlations between performance traits and Strongyle egg counts were usually favourable (i.e. negative) but weak, whereas those with Nematodirus egg counts were generally neutral or slightly positive. Whilst Nematodirus resistance may not necessarily be included in a breeding goal, the results suggest that Nematodirus egg counts can be used as an additional genetic indicator of Strongyle egg counts, at little extra cost. Including the epidemiological consequences of decreasing Strongyle egg counts in benefits of increasing parasite resistance, it is suggested that under UK conditions selection goals that place equal emphasis on live weight and log-transformed egg counts will be a robust means of improving growth rate and decreasing parasite larval challenge.