Fecal egg count (FEC) is an indicative measurement for parasite infection in sheep. Different FEC methods may show inconsistent results. Not accounting for inconsistencies can be problematic when integrating measurements from different FEC methods for genetic evaluation. The objectives of this study were to evaluate the difference in means and variances between two fecal egg counting methods used in sheep—the Modified McMaster (LMMR) and the Triple Chamber McMaster (LTCM); to estimate variance components for the two FEC methods, treating them as two different traits; and to integrate FEC data from the two different methods and estimate genetic parameters for FEC and other gastrointestinal parasite resistance traits. Fecal samples were collected from a commercial Rideau-Arcott sheep farm in Ontario. Fecal egg counting was performed using both LMMR and the LTCM methods. Other parasite resistance trait records were collected from the same farm including eye score (FAMACHA), body condition score (BCS), and body weight (WT). The two FEC methods were highly genetically (0.94) and phenotypically (0.88) correlated. However, the mean and variance between the two FEC methods were significantly different (P < 0.0001). Therefore, re-scaling is required prior to integrating data from the different methods. For the multiple trait analysis, data from the two fecal egg counting methods were integrated (LFEC) by using records for the LMMR when available and replacing missing records with re-standardized LTCM records converted to the same mean and variance of LMMR. Heritability estimates were 0.12 ± 0.04, 0.07 ± 0.05, 0.17 ± 0.06, and 0.24 ± 0.07 for LFEC egg count, FAMACHA, BCS, and WT, respectively. The estimated genetic correlations between FEC and the other parasite resistance traits were low and not significant (P > 0.05) for FAMACHA (r = 0.24 ± 0.32) and WT (r = 0.22 ± 0.19), and essentially zero for BCS (r = −0.03 ± 0.25), suggesting little to no benefit of using such traits as indicators for LFEC.

中文翻译：

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绵羊抗胃肠道寄生虫性状粪便虫卵数测定与遗传参数估计方法的比较

粪卵计数 (FEC) 是衡量绵羊寄生虫感染的指标。不同的 FEC 方法可能会显示不一致的结果。在整合来自不同 FEC 方法的测量值进行遗传评估时，不考虑不一致可能会出现问题。本研究的目的是评估用于绵羊的两种粪便卵计数方法——改良麦克马斯特 (LMMR) 和三室麦克马斯特 (LTCM) 之间的均值和方差差异；估计两种 FEC 方法的方差分量，将它们视为两个不同的特征；并整合来自两种不同方法的 FEC 数据，并估计 FEC 和其他胃肠道寄生虫抗性性状的遗传参数。粪便样本是从安大略省的一家商业 Rideau-Arcott 绵羊农场收集的。使用 LMMR 和 LTCM 方法进行粪便虫卵计数。从同一农场收集其他寄生虫抗性特征记录，包括眼睛评分 (FAMACHA)、身体状况评分 (BCS) 和体重 (WT)。两种 FEC 方法在遗传 (0.94) 和表型 (0.88) 上高度相关。然而，两种 FEC 方法之间的均值和方差存在显着差异（P < 0.0001）。因此，在集成来自不同方法的数据之前，需要重新缩放。对于多重性状分析，通过使用可用的 LMMR 记录并用重新标准化的 LTCM 记录替换缺失的记录来整合来自两种粪便卵计数方法的数据 (LFEC)，该记录转换为相同的 LMMR 均值和方差。遗传力估计值为 0.12 ± 0.04、0.07 ± 0.05、0.17 ± 0.06 和 0.24 ± 0。07 分别用于 LFEC 鸡蛋计数、FAMACHA、BCS 和 WT。FAMACHA (r = 0.24 ± 0.32) 和 WT (r = 0.22 ± 0.19) 的 FEC 与其他寄生虫抗性性状之间估计的遗传相关性较低且不显着 (P > 0.05)，而 BCS (r = −0.03 ± 0.25)，表明使用这些特征作为 LFEC 的指标几乎没有好处。