Thomasen J R, Egger-Danner C, Willam A, Guldbrandtsen B, Lund M S, Sørensen A C
VikingGenetics, DK 8860, Assentoft, Denmark; Center for Quantitative Genetics and Genomics, Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, DK-8960, Tjele, Denmark.
ZuchtData EDV-Dienstleistungen GmbH, 1200 Vienna, Austria.
J Dairy Sci. 2014;97(1):458-70. doi: 10.3168/jds.2013-6599. Epub 2013 Nov 13.
The objective of this study was to evaluate a genomic breeding scheme in a small dairy cattle population that was intermediate in terms of using both young bulls (YB) and progeny-tested bulls (PB). This scheme was compared with a conventional progeny testing program without use of genomic information and, as the extreme case, a juvenile scheme with genomic information, where all bulls were used before progeny information was available. The population structure, cost, and breeding plan parameters were chosen to reflect the Danish Jersey cattle population, being representative for a small dairy cattle population. The population consisted of 68,000 registered cows. Annually, 1,500 bull dams were screened to produce the 500 genotyped bull calves from which 60 YB were selected to be progeny tested. Two unfavorably correlated traits were included in the breeding goal, a production trait (h(2)=0.30) and a functional trait (h(2)=0.04). An increase in reliability of 5 percentage points for each trait was used in the default genomic scenario. A deterministic approach was used to model the different breeding programs, where the primary evaluation criterion was annual monetary genetic gain (AMGG). Discounted profit was used as an indicator of the economic outcome. We investigated the effect of varying the following parameters: (1) increase in reliability due to genomic information, (2) number of genotyped bull calves, (3) proportion of bull dam sires that are young bulls, and (4) proportion of cow sires that are young bulls. The genomic breeding scheme was both genetically and economically superior to the conventional breeding scheme, even in a small dairy cattle population where genomic information causes a relatively low increase in reliability of breeding values. Assuming low reliabilities of genomic predictions, the optimal breeding scheme according to AMGG was characterized by mixed use of YB and PB as bull sires. Exclusive use of YB for production cows increased AMGG up to 3 percentage points. The results from this study supported our hypothesis that strong interaction effects exist. The strongest interaction effects were obtained between increased reliabilities of genomic estimated breeding values and more intensive use of YB. The juvenile scheme was genetically inferior when the increase in reliability was low (5 percentage points), but became genetically superior at higher reliabilities of genomic estimated breeding values. The juvenile scheme was always superior according to discounted profit because of the shorter generation interval and minimizing costs for housing and feeding waiting bulls.
本研究的目的是评估一种适用于小型奶牛群体的基因组育种方案，该群体在使用青年公牛（YB）和后裔测定公牛（PB）方面处于中等水平。将该方案与不使用基因组信息的传统后裔测定计划进行比较，并作为极端情况，与使用基因组信息的青年方案进行比较，在青年方案中，所有公牛在获得后裔信息之前就被使用。选择群体结构、成本和育种计划参数以反映丹麦泽西牛群体，该群体代表小型奶牛群体。该群体由68,000头登记奶牛组成。每年筛选1500头公牛母亲以生产500头基因分型的公牛犊，从中选择60头YB进行后裔测定。育种目标中包括两个负相关性状，一个生产性状（h(2)=0.30）和一个功能性状（h(2)=0.04）。在默认的基因组方案中，每个性状的可靠性提高了5个百分点。采用确定性方法对不同的育种计划进行建模，其中主要评估标准是年度货币遗传增益（AMGG）。贴现利润用作经济结果的指标。我们研究了改变以下参数的影响：（1）由于基因组信息导致的可靠性提高；（2）基因分型公牛犊的数量；（3）作为青年公牛的公牛母亲的父亲比例；（4）作为青年公牛的母牛的父亲比例。即使在基因组信息导致育种值可靠性相对较低增加的小型奶牛群体中，基因组育种方案在遗传和经济上也优于传统育种方案。假设基因组预测的可靠性较低，根据AMGG的最佳育种方案的特点是混合使用YB和PB作为公牛父亲。对生产母牛仅使用YB可使AMGG提高多达3个百分点。本研究结果支持了我们存在强相互作用效应的假设。基因组估计育种值可靠性的提高与更密集地使用YB之间获得了最强的相互作用效应。当可靠性提高较低（5个百分点）时，青年方案在遗传上较差，但在基因组估计育种值可靠性较高时在遗传上变得更优。由于世代间隔较短且将饲养等待公牛的住房和饲料成本降至最低，根据贴现利润，青年方案始终更优。
