Expression of Mitochondrial Respiratory Complex Genes in Liver Tissue of Cattle with Different Feed Efficiency Phenotypes

Feed efficiency is an economically important trait that is likely influenced by complex molecular mechanisms. We utilized the NRC Beef Cattle Model to predict feed intake based on observed gain (and gain based on observed intake), where the NRC model also accounts for breed type, sex and season. The difference between this NRC-predicted feed intake and observed intake is termed model predicted residual consumption (MPRC). Associations between feed efficiency and mitochondrial respiration have been previously reported in the literature. From a study of 177 animals, RNA was extracted from liver samples from 18 animals at each extreme of the MPRC tails (36 samples). Following microarray analysis, quantitative realtime RT-PCR (qPCR) was used to examine expression of several respiratory complex genes including mitochondrial genes COX1, COX2, COX3 (Complex IV) and CYTB (Complex III), and nuclear genes COX4, COX6A1, COX7A2, COX7B, COX7C (Complex IV), SHDB (Complex II) and NQO2 (Complex I). Although expression for some genes was influenced by sire and family, no relationship between expression of any of these genes was found to be associated with feed efficiency phenotype.