Abstract
Polyunsaturated fatty acids (PUFAs) play a role in a wide variety of physiological processes. They are produced by a series of desaturation and elongation reactions. -6-desaturase is a membrane-bound enzyme that catalyzes the conversion of -linolenic acid (C18:3-3) and linoleic acid (C18:2-6) to stearidonic acid (18:4-3) and -linolenic acid (18:3-6). It is encoded by the FADS2 gene located on bovine chromosome 29. The aim of this study was to identify a single nucleotide polymorphism in the FADS2 gene and to determine possible associations with milk fatty acid composition in two breeds of dairy cattle, i.e., Jersey and Polish Holstein-Friesian. Direct DNA sequencing revealed the presence of an A-to-G substitution in intron 3 of the FADS2 gene (rs209202414). Both populations were genotyped with an appropriate PCR-RFLP assay. The following genotype distributions were observed: for Jerseys, AA 0.24, AG 0.63, and GG 0.13; for Polish Holstein-Friesians, AA 0.17, AG 0.40, and GG 0.43. In Jerseys, statistically significant relationships were found between the FASD2 genotypes and the following milk fatty acids: lauric (), behenic (), lignoceric (), oleic (), eicosatrienoic (), and docosadienoic (). In Polish Holstein-Friesian cows, significant associations were observed for erucic () and docosahexaenoic () acids. The study indicated the A-to-G substitution (rs209202414) in the bovine FADS2 gene as a potential genetic marker for fatty acid composition in cattle milk.
Highlights
The feeding of dairy cows is the main factor impacting milk fat composition
Some authors have reported that milk fat composition is modulated by the polymorphisms in genes involved in milk fat synthesis processes, like DGAT1 and SCD1 (Carvajal et al, 2016, Tzompa-Sosa et al, 2016)
DNA fragments overlapping exons 1, 3, and 12 with the parts of adjacent introns of the Fatty acid desaturase-2 (FADS2) gene were sequenced. These analyses revealed the presence of an A to G substitution at position 23 of intron 3 (Fig. 1; GenBank rs209202414)
Summary
The feeding of dairy cows is the main factor impacting milk fat composition. Pasture intake reduces the concentration of saturated fatty acids (SFAs) in the milk of grazing cows (Couvreur et al, 2007; Frigo et al, 2015; Hanuš et al, 2016; Ponnampalamet al., 2018). Genetic factors influence fatty acid (FA) variability. The FA profile in milk changes during lactation, emphasizing the relationship between the physiological status of cow and milk composition (Bastin et al, 2011). The effects on milk FA composition are breed-dependent. The greatest breed differences are observed between Holstein and Jersey milk (with the higher concentrations of SFAs in Jerseys) (Arnould and Soyeurt, 2009). Some authors have reported that milk fat composition is modulated by the polymorphisms in genes involved in milk fat synthesis processes, like DGAT1 and SCD1 (Carvajal et al, 2016, Tzompa-Sosa et al, 2016)
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