Jiang Andrew, Ankersmit-Udy Alex, Turner Sally-Anne, Scholtens Megan, Littlejohn Mathew D, Lopez-Villalobos Nicolas, Proser Colin G, Snell Russell G, Lehnert Klaus
Applied Translational Genetics Group, School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
Dairy Goat Co-operative, Hamilton, New Zealand.
J Anim Sci Biotechnol. 2022 Feb 11;13(1):4. doi: 10.1186/s40104-021-00667-y.
Economically important milk production traits including milk volume, milk fat and protein yield vary considerably across dairy goats in New Zealand. A significant portion of the variation is attributable to genetic variation. Discovery of genetic markers linked to milk production traits can be utilised to drive selection of high-performance animals. A previously reported genome wide association study across dairy goats in New Zealand identified a quantitative trait locus (QTL) located on chromosome 19. The most significantly associated single nucleotide polymorphism (SNP) marker for this locus is located at position 26,610,610 (SNP marker rs268292132). This locus is associated with multiple milk production traits including fat, protein and volume. The predicted effect of selection for the beneficial haplotype would result in an average production increase of 2.2 kg fat, 1.9 kg protein and 73.6 kg milk yield. An outstanding question was whether selection for the beneficial allele would co-select for any negative pleiotropic effects. An adverse relationship between milk production and udder health traits has been reported at this locus. Therefore, a genome wide association study was undertaken looking for loci associated with udder traits.
The QTL and production associated marker rs268292132 was identified in this study to also be associated with several goat udder traits including udder depth (UD), fore udder attachment (FUA) and rear udder attachment (RUA). Our study replicates the negative relationship between production and udder traits with the high production allele at position 19:26,610,610 (SNP marker rs268292132) associated with an adverse change in UD, FUA and RUA.
Our study has confirmed the negative relationship between udder traits and production traits in the NZ goat population. We have found that the frequency of the high production allele is relatively high in the NZ goat population, indicating that its effect on udder conformation is not significantly detrimental on animal health. It will however be important to monitor udder conformation as the chromosome 19 locus is progressively implemented for marker assisted selection. It will also be of interest to determine if the gene underlying the production QTL has a direct effect on mammary gland morphology or whether the changes observed are a consequence of the increased milk volume.
在新西兰，具有经济重要性的产奶性状，包括产奶量、乳脂肪和蛋白质产量，在不同的奶山羊中差异很大。很大一部分变异归因于遗传变异。发现与产奶性状相关的遗传标记可用于推动对高性能动物的选择。此前一项针对新西兰奶山羊的全基因组关联研究确定了一个位于19号染色体上的数量性状基因座（QTL）。该基因座最显著相关的单核苷酸多态性（SNP）标记位于位置26,610,610（SNP标记rs268292132）。这个基因座与多个产奶性状相关，包括脂肪、蛋白质和产量。选择有益单倍型的预测效果将使平均产脂量增加2.2千克、产蛋白量增加1.9千克、产奶量增加73.6千克。一个悬而未决的问题是，选择有益等位基因是否会同时选择出任何负面的多效性效应。在这个基因座上，已报道产奶量与乳房健康性状之间存在不利关系。因此，开展了一项全基因组关联研究，寻找与乳房性状相关的基因座。
在本研究中确定，QTL及与产量相关的标记rs268292132也与几个山羊乳房性状相关，包括乳房深度（UD）、前乳房附着（FUA）和后乳房附着（RUA）。我们的研究重现了产奶量与乳房性状之间的负相关关系，19号染色体上位置26,610,610处的高产等位基因（SNP标记rs268292132）与UD、FUA和RUA的不利变化相关。
我们的研究证实了新西兰山羊群体中乳房性状与产奶性状之间的负相关关系。我们发现，高产等位基因在新西兰山羊群体中的频率相对较高，这表明其对乳房形态的影响对动物健康没有显著危害。然而，随着19号染色体基因座逐步用于标记辅助选择，监测乳房形态将很重要。确定产奶QTL的基础基因是否对乳腺形态有直接影响，或者观察到的变化是否是产奶量增加的结果，也将是很有意义的。
