Vorderwald cattle are a regional cattle breed from the Black Forest in south western Germany. In recent decades, commercial breeds have been introgressed to upgrade the breed in performance traits. On one hand, native genetic diversity of the breed should be conserved. On the other hand, moderate rates of genetic gain are needed to satisfy breeders to keep the breed. These goals are antagonistic, since the native proportion of the gene pool is negatively correlated to performance traits and the carriers of introgressed alleles are less related to the population. Thus, a standard Optimum Contribution Selection (OCS) approach would lead to reinforced selection on migrant contributions (MC). Our objective was the development of strategies for practical implementation of an OCS approach to manage the MC and native genetic diversity of regional breeds. Additionally, we examined the organisational efforts and the financial impacts on the breeding scheme of Vorderwald cattle. We chose the advanced Optimum Contribution Selection (aOCS) to manage the breed in stochastic simulations based on real pedigree data. In addition to standard OCS approaches, aOCS facilitates the management of the MC and the rate of inbreeding at native alleles. We examined two aOCS strategies. Both strategies maximised genetic gain, while strategy (I) conserved the MC in the breeding population and strategy (II) reduced the MC at a predefined annual rate. These two approaches were combined with one of three flows of replacement of sires (FoR strategies). Additionally, we compared breeding costs to clarify about the financial impact of implementing aOCS in a young sire breeding scheme. According to our results, conserving the MC in the population led to significantly (P < 0.01) higher genetic gain (1.16 ± 0.13 points/year) than reducing the MC (0.88 ± 0.10 points/year). In simulation scenarios that conserved the MC, the final value of MC was 57.6% ± 0.004, while being constraint to 58.2%. However, reducing the MC is only partially feasible based on pedigree data. Additionally, this study proves that the classical rate of inbreeding can be managed by constraining only the rate of inbreeding at native alleles within the aOCS approach. The financial comparison of the different breeding schemes proved the feasibility of implementing aOCS in Vorderwald cattle. Implementing the modelled breeding scheme would reduce costs by 1.1% compared with the actual scheme. Reduced costs were underpinned by additional genetic gain in superior simulation scenarios compared to expected genetic gain in reality (+4.85%).

中文翻译：

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在小规模育种计划中实施先进的最佳贡献选择：Vorderwald 牛的前景和挑战。


沃德瓦尔德牛是来自德国西南部黑森林的地方牛品种。近几十年来，商业品种已被引入以升级该品种的性能特征。一方面，应保护该品种的本地遗传多样性。另一方面，需要适度的遗传增益率才能满足育种者的要求，以保留该品种。这些目标是对立的，因为基因库的天然比例与性能特征负相关，而渗入等位基因的携带者与群体的相关性较小。因此，标准的最佳贡献选择（OCS）方法将导致对移民贡献（MC）的强化选择。我们的目标是制定实际实施 OCS 方法的策略，以管理区域品种的 MC 和本地遗传多样性。此外，我们还研究了 Vorderwald 牛育种计划的组织工作和财务影响。我们选择先进的最佳贡献选择（aOCS）来根据真实谱系数据进行随机模拟来管理品种。除了标准 OCS 方法外，aOCS 还有助于管理 MC 和本地等位基因的近交率。我们研究了两种 aOCS 策略。两种策略都最大化了遗传增益，而策略 (I) 保留了育种群体中的 MC，而策略 (II) 以预定的年率减少了 MC。这两种方法与父系替代的三种流程之一（ForR 策略）相结合。此外，我们还比较了育种成本，以阐明在幼年种公马育种计划中实施 aOCS 的财务影响。根据我们的结果，在群体中保留 MC 会导致显着（P < 0.01）更高的遗传增益（1.16 ± 0.13 点/年）比减少 MC（0.88 ± 0.10 点/年）要好。在保留 MC 的模拟场景中，MC 的最终值为 57.6% ± 0.004，同时被限制为 58.2%。然而，根据系谱数据，减少 MC 仅部分可行。此外，这项研究证明，经典的近交率可以通过仅限制 aOCS 方法中本地等位基因的近交率来管理。不同育种方案的财务比较证明了在 Vorderwald 牛中实施 aOCS 的可行性。实施示范养殖方案比实际方案可降低成本1.1%。与现实中的预期遗传增益相比（+4.85%），卓越模拟场景中的额外遗传增益支撑了成本的降低。