Infection with Haemonchus contortus is the most economically important gastrointestinal nematode parasitosis and the most important cause of mortality in sheep production. The aim of this study was to estimate variance components of gastrointestinal parasite resistance traits, maternal efficiency (ME) and ewe adult weight (AW) in Santa Inês breed in tropical conditions. The phenotypic records were collected from 700 animals, belonging to four flocks located south-east and north-east in Brazil. The evaluated traits were as follows: degree of anaemia assessed using the FAMACHA chart (FMC), haematocrit (HCT), white blood cell (WBC), red blood cell (RBC), haemoglobin (HGB), platelets (PLT), faecal egg count (EPGlog ), ME, metabolic maternal efficiency (MME), AW and metabolic ewe adult weight (MAW). From the 700 animals, 576 (82% of the evaluated population) were genotyped with the Ovine SNP12k BeadChip (Illumina, Inc.). Markers with unknown genomic position, located on sex chromosomes, monomorphic, with minor allele frequency <0.05, call rate <90% and with excess heterozygosity were excluded. The variance components were estimated using a single-trait animal model with ssGBLUP procedure. The correlation between the parasite's resistance indicators and the ME suggested that selecting animals with both higher adult weight and ME will also favour the selection of animals with better resistance to gastrointestinal nematodes parasites, specially H. contortus. Therefore, since there are few or no studies with Santa Inês breed in this area, it is important to study those traits to better manage selection programs.

中文翻译：

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Santa Inês 品种胃肠道线虫寄生虫抗性和母体效率指标性状的遗传参数估计

扭曲血球虫感染是经济上最重要的胃肠道线虫寄生虫病，也是绵羊生产中最重要的死亡原因。本研究的目的是估计热带条件下 Santa Inês 品种的胃肠道寄生虫抗性性状、母性效率 (ME) 和母羊成年体重 (AW) 的方差分量。表型记录收集自 700 只动物，属于巴西东南部和东北部的四个羊群。评估的特征如下：使用FAMACHA图表（FMC）评估的贫血程度，血细胞比容（HCT），白细胞（WBC），红细胞（RBC），血红蛋白（HGB），血小板（PLT），粪便卵计数 (EPGlog)、ME、代谢母体效率 (MME)、AW 和代谢母羊成年体重 (MAW)。从 700 只动物中，使用 Ovine SNP12k BeadChip (Illumina, Inc.) 对 576 个（评估群体的 82%）进行基因分型。基因组位置未知、位于性染色体上、单态、次要等位基因频率<0.05、检出率<90%和杂合度过高的标记被排除在外。使用具有 ssGBLUP 程序的单性状动物模型估计方差分量。寄生虫抗性指标与 ME 之间的相关性表明，选择成年体重和 ME 均较高的动物也将有利于选择对胃肠道线虫寄生虫具有更好抗性的动物，特别是扭曲线虫。因此，由于在该领域很少或没有关于 Santa Inês 品种的研究，因此研究这些性状以更好地管理选择程序非常重要。