Mitochondria are organelles that participate in respiration and metabolism to generate ATP. The numbers of mitochondria and their functional capacity may underlie feed efficiency in livestock. Low feed efficient dairy cows contain fewer liver mitochondria than their high feed efficient counterparts (Kennedy et al., 2021). Dairy cows with high residual feed intake (RFI) require more energy (feed) per unit of milk production than those with low RFI and mitochondrial genes are differentially expressed between the two phenotypes (Dorji et al., 2021). Beef steers with a low RFI have greater muscle mitochondrial succinate dehydrogenase activity than their high RFI counterparts indicating that they may have greater numbers of mitochondria and/or activity in the tissue (Fernandez et al., 2020). Because mitochondrial DNA is heritable, an improved understanding of mitochondria copy number and genotype may lead to new genomic selection tools. Sanglard et al (2022) performed low pass sequencing of mitochondrial and nuclear DNA to determine copy number and mitochondrial DNA variations in over 2,000 beef cattle. Results demonstrate that up to 30% of mitochondrial DNA is controlled by genetics. Moreover, mitochondria copy is heritable and likely to respond to selection. For details, please see Sanglard et al (2022) in this issue.
