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

<p>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 (<i>LEP</i>) in New Zealand (NZ) Holstein Friesian <span class="inline-formula">×</span> Jersey (HF <span class="inline-formula">×</span> 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 (<span class="inline-formula"><i>A</i>₃</span>, <span class="inline-formula"><i>B</i>₃</span> and <span class="inline-formula"><i>C</i>₃</span>) 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 <span class="inline-formula"><i>A</i>₃</span> (the most common variant) was associated with a decreased level of C15:1, C18:1 <i>trans</i>-11, C18:1 all <i>trans</i>, C18:2 <i>trans</i>-9, <i>cis</i>-12, C22:0 and C24:0 levels but increased levels of C12:1 and C13:0 <i>iso</i> (<span class="inline-formula"><i>p</i><i><</i>0.05</span>). Variant <span class="inline-formula"><i>B</i>₃</span> was associated with reduced levels of C6:0, C8:0, C11:0, C13:0 and C20:0 but increased C17:0 <i>iso</i> and C24:0 levels (<span class="inline-formula"><i>p</i><i><</i>0.05</span>). Variant <span class="inline-formula"><i>C</i>₃</span> was associated with decreased C17:0 <i>iso</i> levels but increased C20:0 (<span class="inline-formula"><i>p</i><i><</i>0.05</span>) levels. In a genotype model, the <span class="inline-formula"><i>A</i>₃<i>B</i>₃</span> 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 (<span class="inline-formula"><i>p</i><i><</i>0.05</span>). Genotype <span class="inline-formula"><i>A</i>₃<i>C</i>₃</span> was found to be associated with decreased levels of C10:0, C11:0, C13:0 and grouped MCFA (<span class="inline-formula"><i>p</i><i><</i>0.05</span>). This is the first report of findings of this kind in NZ HF <span class="inline-formula">×</span> 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.</p>