Having the ability to control litter size is important for sheep farmers and breeders worldwide. However, making genetic gain in key livestock traits like reproductive performance needs typically a lot of time, and both the fecundity and fertility traits have a great economic importance. Attention has therefore turned to better understanding the genes that control reproductive performance. Of these genes, research has focussed on the growth differentiation growth factor 9 (GDF9) gene (GDF9). In this study, a PCR‐single strand conformation polymorphism (PCR‐SSCP) approach was used to investigate variation in this gene in separate groups of purebred Finnish Landrace sheep, Finnish Landrace × Texel‐cross sheep and composite sheep of undefined breed background, but based on New Zealand Romney‐type genetics. Three GDF9 variants (named A, B and C) were found, and upon DNA sequencing, the nucleotide substitutions c.978A>G, c.994G>A and c.1111G>A were revealed. The frequency of variant A (containing nucleotides c.978A, c.994G and c.1111G) in the Finnish Landrace, Finnish Landrace × Texel‐cross and composite sheep was 0.86, 0.78 and 0.76, respectively. In these three sheep groups, the frequency of B (defined by the presence of nucleotides c.978G and c.994A) was 0.01, 0.03 and 0.23 and for C (containing c.1111A) was 0.13, 0.18 and 0.01, respectively. An animal model was used to estimate the additive effect of fertility data for Finnish Landrace × Texel‐cross sheep and revealed an association between litter size and the c.1111G>A variation (p = .036), but this was not observed for the Finnish Landrace sheep (p = .27) or the composite sheep (p = .17). When all the sheep were analysed together, the presence of c.1111A was associated (p < .05) with increased litter size, when compared to ewes that had c.1111G. Litter size did not differ between sheep with and without c.994A in all three groups of sheep investigated. This study suggests that c.1111A could be a useful genetic marker for improving fecundity in New Zealand sheep breeds and that it could be introgressed into other breeds, but analysis of more sheep will be required to confirm the associations that have been observed here.

中文翻译：

---

鉴定卵母细胞衍生的生长分化生长因子9（GDF9）基因中与新西兰绵羊（Ovis aries）品种的产仔数相关的多态性。

对于世界范围内的绵羊养殖者和饲养员来说，具有控制垫料大小的能力至关重要。但是，要在关键的牲畜性状（如生殖性能）中获得遗传资源通常需要大量时间，而生育力和生育力性状都具有很大的经济意义。因此，注意力转向更好地了解控制生殖性能的基因。在这些基因中，研究集中于生长分化生长因子9（GDF9）基因（GDF9）。在这项研究中，采用PCR单链构象多态性（PCR‐SSCP）方法研究了纯种芬兰纯种长白羊，芬兰纯种×特克塞尔杂交羊和未定义品种背景的复合羊中不同基因组中该基因的变异，但是基于新西兰Romney型遗传学。三发现了GDF9变体（命名为A，B和C），并且在DNA测序后，揭示了核苷酸取代c.978A> G，c.994G> A和c.1111G> A。芬兰长白，芬兰长白×特克塞尔杂交和复合羊变体A（包含核苷酸c.978A，c.994G和c.1111G）的频率分别为0.86、0.78和0.76。在这三个绵羊群中，B的频率（由核苷酸c.978G和c.994A定义）分别为0.01、0.03和0.23，对于C（包含c.1111A）分别为0.13、0.18和0.01。一个动物模型被用来估计芬兰地方品种×特克塞尔杂交羊的生育力数据的累加效应，并揭示了窝产仔数与c.1111G> A变异之间的关联（p  = .036），但是对于芬兰长白羊（p  = .27）或复合羊（p  = .17）。当一起分析所有绵羊时，c.1111A的存在是相关的（p 与具有c.1111G的母羊相比，其产仔数增加了<0.05）。在研究的所有三组绵羊中，有和没有c.994A的绵羊的产仔数没有差异。这项研究表明，c.1111A可能是提高新西兰绵羊品种繁殖力的有用遗传标记，并且可能会渗入其他品种，但是需要对更多绵羊进行分析，以确认此处观察到的关联。