Animal Science Department, North Carolina State University, Raleigh 27695.
Animal Science Department, North Carolina State University, Raleigh 27695.
J Dairy Sci. 2020 Jun;103(6):5302-5313. doi: 10.3168/jds.2019-17846. Epub 2020 Apr 22.
The advent of genomic selection paved the way for an unprecedented acceleration in genetic progress. The increased ability to select superior individuals has been coupled with a drastic reduction in the generation interval for most dairy populations, representing both an opportunity and a challenge. Homozygosity is now rapidly accumulating in dairy populations. Currently, inbreeding depression is managed mostly by culling at the farm level and by controlling the overall accumulation of homozygosity at the population level. A better understanding of how homozygosity and recessive load are related will guarantee continued genetic improvement while curtailing the accumulation of harmful recessives and maintaining enough genetic variability to ensure the possibility of selection in the face of changing environmental conditions. In this review, we present a snapshot of the current dairy selection structure as it relates to response to selection and accumulation of homozygosity, briefly outline the main approaches currently used to manage inbreeding and overall variability, and present some approaches that can be used in the short term to control accumulation of harmful recessives while maintaining sustained selection pressure.
基因组选择的出现为遗传进展的空前加速铺平了道路。选择优秀个体的能力增强，加上大多数奶牛群体的世代间隔急剧缩短，这既是机遇也是挑战。现在，奶牛群体中的同型合子正在迅速积累。目前，主要通过在农场层面进行淘汰和控制群体水平同型合子的总体积累来管理近交衰退。更好地了解同型合子和隐性负荷之间的关系将保证在继续遗传改良的同时，遏制有害隐性的积累，并保持足够的遗传变异，以确保在面对不断变化的环境条件下仍有选择的可能性。在这篇综述中，我们介绍了当前奶牛选择结构与选择响应和同型合子积累的关系，简要概述了目前用于管理近交和总体变异的主要方法，并提出了一些可以在短期内使用的方法来控制有害隐性的积累，同时保持持续的选择压力。
