Studies were conducted to evaluate the potential link between mitochondrial function and biochemistry with the phenotypic expression of feed efficiency (FE) in a single line of broilers fed the same diet. Mitochondria isolated from low FE birds had lower respiratory chain coupling but oxidative phosphorylation capability was either equal or superior to that of mitochondria from broilers with high FE. Higher H2O2 production and higher protein carbonyls (oxidation) was also consistently observed in mitochondria or homogenate from low FE broilers. Respiratory chain complex activities, except for Complex IV activity in the duodenum, were lower in mitochondria from low FE birds. There were differences in gene and protein expression of certain mitochondrial and extra-mitochondrial proteins, but there was no indication that the lower complex activity and respiratory chain coupling in mitochondria from low FE birds is due to a generalized decreased in gene or protein expression. However, three mitochondrial proteins (COX II, cyt c1, and cyt c) and vinculin, a focal adhesion regulator, appear to be differentially expressed with broiler FE phenotype in several tissues. To our knowledge, these studies are the first to demonstrate functional and biochemical differences in mitochondria isolated from tissues of broilers with low and high FE. Furthermore, differences in expression of mitochondrial proteins between high and low FE birds could be exploited to develop FE biomarker(s) to aid selection programs in identifying breeder replacement stock with inferior or superior FE.
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