Abstract
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 (-9-desaturase) gene (SCD) was investigated in New Zealand pasture-grazed Holstein–Friesian 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.880105A/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-untranslated region (3-UTR), and these resulted in three nucleotide sequence variants (named , and . The sequence that would encode valine (V) at position 293 of SCD was linked to 3-UTR variant , and the sequence that would encode alanine (A) was linked to variants and . The frequency of the genotypes was as follows: VV (equivalent to aa: 15.1 %), VA (equivalent to : 50.0 %) and AA (equivalent to : 34.9 %). The cows with the 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 variant cows (). Effects of c.*1783A/G and c.*2066T/C/G on milk fat composition were also found for the AA cows. The presence of was associated with decreased levels of C16:1 (), C17:1 (), C18:2 cis-9, trans-13 (), C18:2 cis-9, trans-12 () FA and C16:1 FA index (). The presence of was associated with increased levels of C13:0 iso FAs (), monounsaturated FA (MUFA; ) and C12:1 ().
Highlights
Stearoyl-CoA desaturase (SCD), named 9-desaturase, can introduce a double bond at the 9,10 position in a large spectrum of fatty acids (FAs), and it is a rate-limiting enzyme in catalysing the synthesis of monounsaturated fatty acids (MUFAs) from saturated FAs (SFAs) (Nakamura et al, 2004; Paton et al, 2009)
The main substrates for SCD are C16:0 and C18:0 FA, which can be converted into C16:1 cis9 and C18:1 cis-9 (Paton et al, 2009), but it can catalyse the formation of cis-9, trans-11 conjugated linoleic acid (CLA) from C18:1 trans-11 (Ntambi et al, 2004)
The expression of SCD occurs at high levels (Bernard et al, 2005; Bionaz et al, 2008; McDonald et al, 1973), and it is considered to be important with respect to milk fat composition in these animals (Gautier et al, 2006)
Summary
Stearoyl-CoA desaturase (SCD), named 9-desaturase, can introduce a double bond at the 9,10 position in a large spectrum of fatty acids (FAs), and it is a rate-limiting enzyme in catalysing the synthesis of monounsaturated fatty acids (MUFAs) from saturated FAs (SFAs) (Nakamura et al, 2004; Paton et al, 2009). Ntambi et al (2004) reported that dietary factors could regulate the expression of SCD, and the expression patterns of SCD in cows that are grazing outdoor on pasture might be different to cows that are fed indoors on supplements. This is supported by the observation of Elgersma (2015) that milk from grazing-based
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