Departamento de Genética, Ecologia e Evolução, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, Ontario, Canada.
J Anim Breed Genet. 2023 Sep;140(5):532-548. doi: 10.1111/jbg.12777. Epub 2023 Apr 26.
Individual variation in milk fatty acid (FA) composition has been partially attributed to stearoyl-CoA desaturase 1 (SCD1) gene polymorphisms in taurine breeds, but much less is known for Zebu breeds. This study investigated the phenotypic variation in milk FA composition, and the influence of SCD1 variants on this trait and on milk fat desaturase indices (DI) in Gir cows. The functional impact of SCD1 variants was predicted using bioinformatics tools. Milk and blood samples were collected from 312 cows distributed in 10 herds from five states of Brazil. SCD1 variants were identified through target sequencing, and milk FA composition was determined by gas chromatography. Phenotypic variation in milk FA composition fell within the range reported for taurine breeds, with SCD index showing the lowest variation among the DI. Fourteen SCD1 variants were identified, six of which not previously described. Regarding the A293V polymorphism, all cows were homozygous for the C allele (coding for alanine), whereas all genotypes were detected for the second SNP affecting the 293 codon (G > A), with compelling evidence for functional effects. Significant associations (based on raw p-values) were found between this SNP and C12:0, cis-9, trans-11 CLA and short-chain FA, and between another SNP (rs523411937) and C15:0 and odd-chain linear FA. A new SNP on Chr26:21277069 was associated with trans-11 C18:1, cis-9, trans-11 CLA, C18:3 n-3 and n-3 FA. These findings indicate that SCD1 polymorphisms also contributes to the phenotypic variation in milk FA composition of Gir cows, with potential use in their breeding programmes.
奶牛乳脂肪酸（FA）组成的个体差异部分归因于 Taurine 品种的硬脂酰辅酶 A 去饱和酶 1（SCD1）基因多态性，但对 Zebu 品种的了解较少。本研究调查了 Gir 奶牛乳 FA 组成的表型变异，以及 SCD1 变体对该性状和乳脂肪去饱和酶指数（DI）的影响。使用生物信息学工具预测了 SCD1 变体的功能影响。从巴西五个州的 10 个牛群中收集了 312 头奶牛的牛奶和血液样本。通过靶向测序鉴定 SCD1 变体，通过气相色谱法测定乳 FA 组成。乳 FA 组成的表型变异范围与 Taurine 品种报道的范围一致，SCD 指数在 DI 中表现出最低的变异。鉴定出 14 种 SCD1 变体，其中 6 种是以前未描述的。关于 A293V 多态性，所有奶牛均为 C 等位基因（编码丙氨酸）的纯合子，而第二个影响 293 密码子（G> A）的 SNP 检测到所有基因型，并有确凿的功能影响证据。该 SNP 与 C12:0、顺式-9、反式-11 CLA 和短链 FA 以及另一个 SNP（rs523411937）与 C15:0 和奇数链线性 FA 之间存在显著关联（基于原始 p 值）。Chr26:21277069 上的一个新 SNP 与 trans-11 C18:1、cis-9、trans-11 CLA、C18:3 n-3 和 n-3 FA 相关。这些发现表明，SCD1 多态性也有助于 Gir 奶牛乳 FA 组成的表型变异，具有在其育种计划中的潜在用途。
