Impact of young ewe fertility rate on risk and genetic gain in sheep-breeding programs using genomic selection
Impact of young ewe fertility rate on risk and genetic gain in sheep-breeding programs using genomic selection
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DOI：
10.1071/an15321
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发表时间：
2017-01-01
影响因子：
1.4
通讯作者：
van der Werf, J. H. J.
中科院分区：
文献类型：
--
作者：
Newton, J. E.;Brown, D. J.;van der Werf, J. H. J.
基因组选择在绵羊育种计划中可能有用，特别是如果公羊和母羊首次交配的年龄比当前行业惯例更早的话。然而，众所周知，年轻母羊（1 岁）的生育率比成熟母羊的生育率更低且变化更大。本研究的目的是评估年轻母羊生育率如何影响澳大利亚绵羊育种计划中的风险和预期遗传增益，该计划利用基因组信息并选择不同年龄的母羊和公羊。该研究使用随机模拟来模拟不同羊群年龄结构和幼母羊的生育水平，无论是否有美利奴羊和母羊育种计划的基因组信息。 10 年选择的结果用于根据遗传增益的平均值和变化来比较育种计划。公羊和母羊的年龄、雄性基因组信息的可用性和幼母羊的生育水平均显着（P < 0.05）影响预期的遗传增益。较高的幼母羊生育率显着增加了预期的遗传增益。年轻母羊的低生育率（10%）导致的净遗传增益类似于直到 19 个月大才选择母羊，并且不会增加育种计划风险，因为遗传增益低于后期选择两性育种计划的可能解决方案范围的可能性为零。 1 岁公羊的基因组信息显着高于 2 岁公羊（P < 0.05）。除非获得基因组信息，否则公羊的早期交配不会为美利奴羊毛育种计划带来更大的收益，并且会增加育种计划的风险。结论是，基因组信息降低了 7 个月大时选择替代品的相关风险。如果生育水平能够达到 10% 以上，遗传进展就不太可能受到不利影响。对于饲养者来说，年轻母羊的加入是否是一个可行的管理决策，将取决于其年轻母羊可以达到的生育水平以及与母羊早期交配相关的其他成本。
Genomic selection could be useful in sheep-breeding programs, especially if rams and ewes are first mated at an earlier age than is the current industry practice. However, young-ewe (1 year old) fertility rates are known to be lower and more variable than those of mature ewes. The aim of the present study was to evaluate how young-ewe fertility rate affects risk and expected genetic gain in Australian sheep-breeding programs that use genomic information and select ewes and rams at different ages. The study used stochastic simulation to model different flock age structures and young-ewe fertility levels with and without genomic information for Merino and maternal sheep-breeding programs. The results from 10 years of selection were used to compare breeding programs on the basis of the mean and variation in genetic gain. Ram and ewe age, availability of genomic information on males and young-ewe fertility level all significantly (P < 0.05) affected expected genetic gain. Higher young-ewe fertility rates significantly increased expected genetic gain. Low fertility rate of young ewes (10%) resulted in net genetic gain similar to not selecting ewes until they were 19 months old and did not increase breeding-program risk, as the likelihood of genetic gain being lower than the range of possible solutions from a breeding program with late selection of both sexes was zero. Genomic information was of significantly (P < 0.05) more value for 1-year-old rams than for 2-year-old rams. Unless genomic information was available, early mating of rams offered no greater gain in Merino breeding programs and increased breeding-program risk. It is concluded that genomic information decreases the risk associated with selecting replacements at 7 months of age. Genetic progress is unlikely to be adversely affected if fertility levels above 10% can be achieved. Whether the joining of young ewes is a viable management decision for a breeder will depend on the fertility level that can be achieved in their young ewes and on other costs associated with the early mating of ewes.