Interbull has been responsible for comparing dairy bulls across countries since the mid-1980s. The current methodology is called MACE (multiple across country evaluations) which has been in use since 1995. Now that genomic data are being utilized in many countries, this has led to two serious problems. The first is that of preselection of young bulls such that the young animals are no longer a random sample of progeny from a sire by dam mating pair. Secondly, some countries are becoming less willing to share genomic data with Interbull. Both issues raise concern over the future of Interbull and international comparisons. This paper suggests a competition model as a potential replacement for MACE. The competition model makes pairwise comparisons between all pairs of bulls within a country and combines these differences across countries through bulls that are used in more than one country. Pedigree information is ignored as are all genomic data because bulls are treated as fixed. The model produces one international ranking of bulls averaging out any genotype by environment interactions which may exist. The competition model is illustrated by a small example. The limitations and advantages of the competition model are discussed.

中文翻译：

---

牲畜国际比较的竞争模型

自 1980 年代中期以来，Interbull 一直负责比较不同国家的奶牛。当前的方法称为 MACE（多个国家/地区评估），自 1995 年以来一直在使用。现在许多国家都在使用基因组数据，这导致了两个严重的问题。第一个是预选年轻公牛，这样年轻的动物不再是来自母猪交配对的父亲的随机后代样本。其次，一些国家越来越不愿意与 Interbull 共享基因组数据。这两个问题都引起了人们对 Interbull 和国际比较的未来的担忧。本文提出了一种竞争模型作为 MACE 的潜在替代品。竞争模型在一个国家内的所有公牛对之间进行成对比较，并通过在一个以上国家使用的公牛将这些不同国家之间的差异结合起来。与所有基因组数据一样，谱系信息被忽略，因为公牛被视为固定的。该模型产生一个公牛的国际排名，通过可能存在的环境相互作用对任何基因型进行平均。通过一个小例子说明了竞争模型。讨论了竞争模型的局限性和优势。