Association of mitochondrial biochemistry and electron transport chain protein expression with feed efficiency in Angus cattle

The objectives of this study were to determine the relationships between feed efficiency (FE, gain/feed) and various indices of mitochondria biochemistry in cattle and also to determine if relationships exist between traditional production and carcass traits and various indices of mitochondrial biochemistry. For this 2-yr study, 92 head/year were individually fed for 130 d via a Calan Broadbent Feeding system that allowed for individual animal intake to be recorded. Animals were fed five finishing rations (stepwise) throughout the feeding period. Animals were harvested at a commercial packing plant and muscle ( Sternohyoideus) samples were obtained from all animals. Mitochondria were isolated using differential centrifugation methods. Activities of respiratory chain complexes were measured using spectrophotometric methods. Oxidized protein (carbonyl) and immunoreactive mitochondrial proteins were analyzed using Western blots. Activities of all respiratory chain complexes (I-V) were higher (P < 0.02) in Low compared to High FE steers. A total of 11 respiratory chain proteins and one membrane protein were analyzed. Results concluded that certain proteins were differentially expressed in high vs. low feed efficiency cattle. Significant correlations were found between average daily gain, feed intake, feed efficiency (gain/feed), and residual feed intake with measures of respiratory chain complex activities. There were no significant relationships with mitochondria activity and carcass traits. Weaning weight was significantly related to respiratory chain complex activities. These data aid in the complex understanding of the underlying polygenic trait of efficiency of feed utilization and will lead to a better understand this complex trait.