Variation in the stearoyl-CoA desaturase gene (SCD) and its influence on milk fatty acid composition in late-lactation dairy cattle grazed on pasture

Gene markers have become useful tools for improving animal genetics and breeding since they improve the accuracy of selection for superior breeding stock. In this study, the stearoyl-CoA desaturase ([Formula: see text]-9-desaturase) gene (SCD) was investigated in New Zealand pasture-grazed Holstein–Friesian [Formula: see text] Jersey cows. Three nucleotide substitutions were identified in exon 5 of the gene (c.702A/G, c.762T/C and c.878C/T), and a single nucleotide substitution was identified in intron 5 (c.880 [Formula: see text] 105A/G). The c.878C/T substitution would, if expressed, result in the amino acid substitution p.A293V. Four nucleotide substitutions (c.*1783A/G, c.*1883C/T, c.*1984G/A and c.*2066T/C/G) were identified in the 3 [Formula: see text]-untranslated region (3 [Formula: see text]-UTR), and these resulted in three nucleotide sequence variants (named [Formula: see text] , [Formula: see text] and [Formula: see text]. The sequence that would encode valine (V) at position 293 of SCD was linked to 3 [Formula: see text]-UTR variant [Formula: see text] , and the sequence that would encode alanine (A) was linked to variants [Formula: see text] and [Formula: see text]. The frequency of the genotypes was as follows: VV (equivalent to aa: 15.1 %), VA (equivalent to [Formula: see text]: 50.0 %) and AA (equivalent to [Formula: see text]: 34.9 %). The cows with the [Formula: see text] variant produced less C10:1, C12:1 and C14:1 fatty acid (FA) but more C10:0, C11:0, C14:0, C16:1 and C18:2 FA than the [Formula: see text] variant cows ([Formula: see text]). Effects of c.*1783A/G and c.*2066T/C/G on milk fat composition were also found for the AA cows. The presence of [Formula: see text] was associated with decreased levels of C16:1 ([Formula: see text]), C17:1 ([Formula: see text]), C18:2 cis-9, trans-13 ([Formula: see text]), C18:2 cis-9, trans-12 ([Formula: see text]) FA and C16:1 FA index ([Formula: see text]). The presence of [Formula: see text] was associated with increased levels of C13:0 iso FAs ([Formula: see text]), monounsaturated FA (MUFA; [Formula: see text]) and C12:1 ([Formula: see text]).