Phenotypic variation in milk fatty acid composition and its association with stearoyl-CoA desaturase 1 (SCD1) gene polymorphisms in Gir cows.

Abstract

Individual variation in milk fatty acid (FA) composition has been partially attrib- uted 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 composi- tion was determined by gas chromatography. Phenotypic variation in milk FA

composition fell within the range reported for taurine breeds, with SCD18 index

showing the lowest variation among the DI. Fourteen SCD1 variants were identi- fied, six of which not previously described. Regarding the A293V polymorphism,

all cows were homozygous for the C allele (coding for alanine), whereas all gen- otypes 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 lin- ear 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 polymor- phisms also contributes to the phenotypic variation in milk FA composition of

Gir cows, with potential use in their breeding programmes.