基因型与环境互作和异方差性影响卡提丹羊寄生虫抗性的表达。

Genotype by environment interaction and heteroscedasticity influence the expression of parasite resistance in Katahdin sheep.

机构信息

Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.

USDA, ARS, Dale Bumpers Small Farms Research Center, Booneville, AR 72927, USA.

出版信息

J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad228.

DOI:10.1093/jas/skad228

PMID:37407224

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC10402657/

Abstract

Increasingly, sheep producers are choosing breeds that express resistance to gastrointestinal parasites due to reduced efficacy of anthelminthic drugs. One such breed is Katahdin. Katahdins are raised in various climates and management systems in the United States, which can be combined into eco-management clusters to describe production environments more holistically. The objectives of this study were to determine if genotype by environment interaction (G × E) and heteroscedasticity existed across these eco-management clusters for traits indicative of parasite resistance. Body weights (BW), FAMACHA scores (FAM), and fecal egg counts (FEC) were collected at around 90 d in 3,527 Katahdin lambs delineated into nine eco-management clusters. A tri-variate animal model including birth-rearing type, sex, and dam age (as a quadratic covariate) as fixed effects, and eco-management cluster, direct additive, uncorrelated maternal environmental (for BW), and residual as random effects, was fitted with ASReml. Heritability estimates for BW, FEC, and FAM were 0.36 ± 0.07, 0.31 ± 0.07, and 0.26 ± 0.05, respectively. The genetic (additive) correlation between BW with FEC was -0.26 ± 0.08 and with FAM was -0.16 ± 0.08, and thereby favorable. Heritabilities were also estimated univariately within eco-management clusters and ranged from 0.30 ± 0.05 to 0.37 ± 0.05 for BW, 0.18 ± 0.12 to 0.50 ± 0.13 for FEC, and 0.07 ± 0.06 to 0.40 ± 0.19 for FAM. Significant genetic and phenotypic heteroscedasticity among eco-management clusters was detected in FEC and FAM. A sire by eco-management cluster interaction term was added to the initial model fitted to evaluate G × E. This interaction defined substantial variation (P < 0.01) in all traits and explained 12% (FEC) to 20% (BW) of the phenotypic variation. Accounting for G × E and heteroscedasticity in the design and implementation of breeding programs may introduce operational challenges. Still, doing so would improve the efficacy of selection programs to improve parasite resistance.

摘要

由于驱虫药物效果降低，越来越多的绵羊养殖者选择具有抗胃肠道寄生虫能力的品种。卡他丁羊就是其中之一。卡他丁羊在美国的各种气候和管理系统中饲养，可以组合成生态管理群，更全面地描述生产环境。本研究的目的是确定在这些生态管理群中，是否存在基因型与环境互作（G×E）和异方差性，以及是否存在与寄生虫抗性相关的性状。在 3527 只卡他丁羔羊大约 90 天时，采集体重（BW）、FAMACHA 评分（FAM）和粪便卵计数（FEC），并将羔羊划分为 9 个生态管理群。采用三元动物模型，包括出生饲养类型、性别和母羊年龄（二次协变量）作为固定效应，生态管理群、直接加性、不相关母环境（BW）和残差作为随机效应，用 ASReml 进行拟合。BW、FEC 和 FAM 的遗传力估计值分别为 0.36±0.07、0.31±0.07 和 0.26±0.05。BW 与 FEC 之间的遗传（加性）相关系数为-0.26±0.08，与 FAM 的相关系数为-0.16±0.08，均为有利相关。在生态管理群内也分别进行了单变量遗传力估计，BW 的遗传力范围为 0.30±0.05 至 0.37±0.05，FEC 的遗传力范围为 0.18±0.12 至 0.50±0.13，FAM 的遗传力范围为 0.07±0.06 至 0.40±0.19。在 FEC 和 FAM 中检测到生态管理群之间存在显著的遗传和表型异方差性。初始模型中添加了一个与生态管理群互作的父本效应项，以评估 G×E。该互作解释了所有性状的大部分变异（P<0.01），占表型变异的 12%（FEC）至 20%（BW）。在设计和实施繁殖计划时考虑 G×E 和异方差性可能会带来操作上的挑战。然而，这样做可以提高选择计划的效果，以提高寄生虫抗性。