Garcia-Baccino C A, Pineda-Quiroga C, Astruc J M, Ugarte E, Legarra A
INRA, GenPhySE, Castanet-Tolosan 31320, France.
Departamento de Producción Animal, Facultad de Agronomía, Universidad de Buenos Aires, Buenos Aires C1417DSQ, Argentina.
JDS Commun. 2022 May 21;3(4):260-264. doi: 10.3168/jdsc.2021-0195. eCollection 2022 Jul.
Spanish Latxa and French Manech are dairy sheep breeds that split into Blond (Latxa Cara Rubia, LCR; Manech Tête Rousse, MTR) and Black (Latxa Cara Negra of Navarre, LCN; Manech Tête Noire, MTN) strains. Exchange of genetic material (artificial insemination doses) is becoming more and more frequent across these breeds, within color, to boost both genomic precision using a larger reference population and genetic progress using a larger selection base. This exchange leads to some rams having descendance across both countries. However, additional gains can only be achieved if the selected traits are genetically similar across countries. The objective of this work was to estimate the genetic correlation across breeds for milk yield. We combine across-country, within-color records, pedigree, and marker information. The number of animals with records oscillates from 65,000 (LCN) to 544,000 (MTR), whereas the number of connecting artificial insemination rams (with more than 10 daughters in the other country) is 381 MTR rams in LCR and 58 MTN rams in LCN. Blond strains had a stronger and more extended-in-time connection. The number of genotyped rams goes from 328 (LCN) to 4,901 (MTR). The relatedness of populations was assessed by principal component analysis and F coefficients. The genetic correlation was estimated using 2 (one per color) 2-trait models (each country a trait), including all available data (records, pedigree and genotypes), by maximum profile likelihood while fixing other variance components to within-population estimates. Results showed a closer genetic relationship of Blond strains than of Black strains (F: 0.01 vs. 0.05, respectively). Genetic correlation estimates for milk yield were 0.70 in both cases. Based on F distances, we expected a lower correlation for Black strains than for Blond ones if dominance or epistasis are important. Thus, we attribute the value of this correlation not being close to 1 mostly to genotype-by-environment interaction, including on-farm management and trait modeling. Regardless, the correlation of 0.7 across populations is encouraging for future joint work of Latxa and Manech breeders, including joint genetic evaluations.
西班牙拉查羊和法国马内克羊是乳用绵羊品种，它们分为金色（拉查红面羊，LCR；马内克红头羊，MTR）和黑色（纳瓦拉黑面拉查羊，LCN；马内克黑头羊，MTN）品系。在这些品种内部，不同颜色品系之间的遗传物质交换（人工授精剂量）越来越频繁，目的是通过扩大参考群体提高基因组准确性，并通过扩大选择基础促进遗传进展。这种交换导致一些公羊在两个国家都有后代。然而，只有当所选性状在不同国家的遗传相似时，才能实现额外的遗传进展。本研究的目的是估计不同品种间产奶量的遗传相关性。我们整合了跨国、同颜色的记录、系谱和标记信息。有记录的动物数量在65,000头（LCN）到544,000头（MTR）之间波动，而连接两国的人工授精公羊数量（在另一个国家有超过10个女儿）为：LCR中有381头MTR公羊，LCN中有58头MTN公羊。金色品系的联系更强且持续时间更长。基因分型公羊的数量从328头（LCN）到4,901头（MTR）不等。通过主成分分析和F系数评估群体间的亲缘关系。使用2个（每种颜色1个）二性状模型（每个国家为一个性状）估计遗传相关性，包括所有可用数据（记录、系谱和基因型），通过最大轮廓似然法，同时将其他方差成分固定为群体内估计值。结果表明，金色品系的遗传关系比黑色品系更紧密（F值分别为0.01和0.05）。两种情况下产奶量的遗传相关性估计值均为0.70。基于F距离，如果显性或上位性起重要作用，我们预计黑色品系的相关性低于金色品系。因此，我们将这种相关性的值未接近1主要归因于基因型与环境的相互作用，包括农场管理和性状建模。无论如何，群体间0.7的相关性对于拉查羊和马内克羊育种者未来的联合工作，包括联合遗传评估来说是令人鼓舞的。
