Genetics and breeding of Taurine-Indicine crossbred dairy cattle

该项目将通过研究牛磺酸-吲哚杂交奶牛的遗传和育种，为可持续的粮食生产做出贡献。许多国家都使用牛磺酸和吲哚杂交牛，以利用其适合性和牛磺酸品种的生产力。该项目将把重点放在占巴西奶牛群80%的吉罗兰多人身上。这一群体的基础是当地适应的印度乳品品种Gyr。Gyr奶牛与多产的牛磺酸奶牛品种荷斯坦杂交。由此产生的吉罗兰多奶牛被反复与纯种或杂交公牛杂交。重复杂交造成了适应性和生产力的巨大变异，大变异既是问题，也是机遇。这是一个问题，因为在低投入环境中适应性不足，在高投入环境中生产力不足。这两个极端都在降低奶牛的生产性能，浪费自然资源。即使适应性和生产力的平均水平与环境相匹配，牛磺酸和吲哚基因组的分离也在增加亲本品种之外的变异。这种额外的变异是由两个亚种基因组的加性遗传效应和非加性遗传效应的相互作用以及基因组与环境的相互作用所驱动的。这一巨大的变异是优化育种的机会，它将使遗传学与环境相匹配，并创造新的改进的基因组组合。该项目将包括三个工作包。第一个工作包将从群体遗传学的角度分析基因组数据，以量化两个亚种品种之间的差异和杂交品种的遗传组成。这项工作将利用种群遗传学的最新进展，通过两个亚种基因组的重组来推断整个种群树。第二个工作包将扩展种群遗传分析，对不同巴西环境和管理实践下的奶牛性能进行定量遗传分析。这将量化相加和非相加遗传变异的大小和环境相互作用的基因型，并将这种变异映射到两个亚种基因组的区域。第三个工作包将利用之前的工作包来建立吉罗兰多种群的数字双胞胎(建模/随机模拟)育种计划，并与利益相关者合作评估各种育种策略。其目的将是制定一项战略，不断匹配和改进巴西环境中的适应性和生产力。这将使用基于表型和基因组数据的选择性育种和交配策略。

This project will contribute to sustainable food production by studying the genetics and breeding of Taurine-Indicine crossbred dairy cattle. Taurine-Indicine crossbred cattle is used in many countries to harness the fitness of Indicine breeds and the productivity of Taurine breeds. This project will focus on the Girolando population that represents 80% of the Brazilian dairy herd. Foundation for this population is the locally adapted Indicine dairy breed Gyr. Gyr cows are crossed with the productive Taurine dairy breed Holstein. The resulting Girolando cows are repeatedly crossed with the purebred or crossbred bulls. The repeated crossbreeding is causing large variation in adaptability and productivity.The large variation is both a problem and an opportunity. It is a problem because of inadequate adaptability in low-input environments and inadequate productivity in high-input environments. Both extremes are reducing dairy performance and wasting natural resources. Even when the mean level of adaptability and productivity match the environment the segregation of Taurine and Indicine genomes is increasing variation beyond the parent breeds. This additional variation is driven by the segregation of additive genetic effects and the interaction of non-additive genetic effects of the two subspecies genomes as well as genome by environment interactions. This large variation is an opportunity for optimised breeding that would match genetics to the environment and create new improved genome combinations.This project will comprise three work-packages.The first work-package will analyse genomic data from population genetic perspective to quantify differences between the two sub-species breeds and the genetic composition of crossbreds. This work will make use of recent advances in population genetics to infer whole population trees with recombination across the two subspecies genomes.The second work-package will expand the population genetic analyses with quantitative genetic analyses of dairy performance under various Brazilian environments and management practices. This will quantify the magnitude of additive and non-additive genetic variation and genotype by environment interaction as well as map this variation to regions of the two subspecies genomes.The third work-package will leverage the previous work-packages to build a digital twin (modelling / stochastic simulation) breeding programme of the Girolando population and evaluate various breeding strategies in collaboration with stakeholders. The aim will be to develop a strategy for continuous matching and improvement of adaptability and productivity in Brazilian environments. This will use selective breeding and mating strategies based on phenotypic and genomic data.