Variation in bovine leptin gene affects milk fatty acid composition in New Zealand Holstein Friesian × Jersey dairy cows.

Leptin is a protein hormone secreted from white adipose tissue. It regulates food/feed intake, body weight, immune function and reproduction. In our investigation, the polymerase chain reaction (PCR) amplification coupled with single-strand conformational polymorphism (SSCP) analysis was used to reveal variation in bovine leptin gene () in New Zealand (NZ) Holstein Friesian   Jersey (HF   J) dairy cows. Subsequent sequence analysis of a 430 bp amplicon spanning the entirety of exon 3 and part of the intron 2 region revealed three variant sequences ( , and ) containing a total of five nucleotide substitutions, all of which have been reported previously. Using general linear mixed-effect model analyses, the presence of variant (the most common variant) was associated with a decreased level of C15:1, C18:1 -11, C18:1 all , C18:2 -9, -12, C22:0 and C24:0 levels but increased levels of C12:1 and C13:0 ( ). Variant was associated with reduced levels of C6:0, C8:0, C11:0, C13:0 and C20:0 but increased C17:0 and C24:0 levels ( ). Variant was associated with decreased C17:0 levels but increased C20:0 ( ) levels. In a genotype model, the genotype was associated with increased levels of C22:0 and C24:0 but decreased C8:0, C10:0, C11:0, C13:0, C15:0 and grouped medium-chain fatty acid (MCFA) levels ( ). Genotype was found to be associated with decreased levels of C10:0, C11:0, C13:0 and grouped MCFA ( ). This is the first report of findings of this kind in NZ HF   J cows, and they suggest that variation in exon 3 of bovine leptin gene could be explored as a means of decreasing the concentration of saturated fatty acids in milk.