Breed-specific factors influence embryonic lipid composition: comparison between Jersey and Holstein.

Some embryos exhibit better survival potential to cryopreservation than others. The cause of such a phenotype is still unclear and may be due to cell damage during cryopreservation, resulting from overaccumulation and composition of lipids. In cattle embryos, in vitro culture conditions have been shown to impact the number of lipid droplets within blastomeres. Thus far, the impact of breed on embryonic lipid content has not been studied. In the present study were compared the colour, lipid droplet abundance, lipid composition, mitochondrial activity and gene expression of in vivo-collected Jersey breed embryos, which are known to display poor performance post-freezing, with those of in vivo Holstein embryos, which have good cryotolerance. Even when housed and fed under the same conditions, Jersey embryos were found to be darker and contain more lipid droplets than Holstein embryos, and this was correlated with lower mitochondrial activity. Differential expression of genes associated with lipid metabolism and differences in lipid composition were found. These results show genetic background can impact embryonic lipid metabolism and storage.