Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada.
Ontario Ministry of Agriculture, Food and Rural Affairs, Elora, ON, Canada.
J Anim Sci. 2021 Dec 1;99(12). doi: 10.1093/jas/skab341.
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.
粪便卵计数（FEC）是绵羊寄生虫感染的指示性测量。不同的 FEC 方法可能会显示出不一致的结果。在对来自不同 FEC 方法的测量值进行遗传评估时，如果不考虑这些差异，可能会出现问题。本研究的目的是评估两种绵羊粪便卵计数方法（改良麦克马斯特法[LMMR]和三重腔麦克马斯特法[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；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特征的遗传参数。粪便样本取自安大略省一家商业的罗多-阿科特绵羊农场。使用 LMMR 和 LTCM 方法进行粪便卵计数。来自同一农场的其他寄生虫抗性特征记录包括眼评分（FAMACHA）、体况评分（BCS）和体重（WT）。两种 FEC 方法在遗传上（0.94）和表型上（0.88）高度相关。然而，两种 FEC 方法之间的均值和方差存在显著差异（P < 0.0001）。因此，在整合来自不同方法的数据之前，需要重新缩放。对于多特征分析，通过使用 LMMR 的记录（在可用时）整合来自两种粪便卵计数方法的数据（LFEC），并使用重新标准化的 LTCM 记录替换缺失的记录，这些记录转换为与 LMMR 相同的均值和方差。LFEC 卵计数、FAMACHA、BCS 和 WT 的遗传率估计值分别为 0.12 ± 0.04、0.07 ± 0.05、0.17 ± 0.06 和 0.24 ± 0.07。FEC 与其他寄生虫抗性特征之间的遗传相关性估计值较低且不显著（P > 0.05），FAMACHA（r = 0.24 ± 0.32）和 WT（r = 0.22 ± 0.19），BCS（r = -0.03 ± 0.25），这表明使用这些特征作为 LFEC 的指标几乎没有益处。
