The objective of this study was to determine the extent to which genetic selection for residual feed intake (RFI) impacts electron leakage and reactive oxygen species (ROS) production in mitochondria from muscle and liver tissue. Understanding how genetic selection for RFI impacts animal physiology and growth efficiency is of the utmost importance as the world population increases. Production efficiency is tied directly to energy use. Mitochondria were used in this study because they produce 90% of the ATP in the body and use a large majority of dietary energy. Mitochondria were isolated from both muscle and liver tissue from pigs genetically selected for RFI (n = 8 per RFI line; 34 ± 4 kg). A 2,7-dichlorofluorscein diacetate assay was used to detect differences in hydrogen peroxide production between the more efficient low RFI line and the less efficient high RFI line. Our hypothesis was that greater efficiency would be linked to less ROS production from the mitochondria. There was less ROS production in mitochondria from the white portion of the semitendinosus in the low RFI line compared with the high RFI line, when both NADH and Flavin Adenine Dinucleotide (FADH2) energy substrates were used (glutamate and succinate, respectively). Additionally, mitochondria from the red portion of the semitendinosus in the low RFI line had less ROS production when succinate was used as an energy substrate (P < 0.05). A positive correlation was observed between RFI and ROS in mitochondria from the LM. These data indicate genetic selection for RFI may influence mitochondrial ROS production and efficiency of pork production. ABSTRACT: The objective of this study was to determine the extent to which genetic selection for residual feed intake (RFI) impacts electron leakage and reactive oxygen species (ROS) production in mitochondria from muscle and liver tissue. Understanding how genetic selection for RFI impacts animal physiology and growth effi ciency is of the utmost importance as the world population increases. Production effi ciency is tied directly to energy use. Mitochondria were used in this study because they produce 90% of the ATP in the body and use a large majority of dietary energy. Mitochondria were isolated from both muscle and liver tissue from pigs genetically selected for RFI (n = 8 per RFI line; 34 ± 4 kg). A 2,7-dichlorofl uorscein diacetate assay was used to detect differences in hydrogen peroxide production between the more effi cient low RFI line and the less effi cient high RFI line. Our hypothesis was that greater effi ciency would be linked to less ROS production from the mitochondria. There was less ROS production in mitochondria from the white portion of the semitendinosus in the low RFI line compared with the high RFI line, when both NADH and Flavin Adenine Dinucleotide (FADH2) energy substrates were used (glutamate and succinate, respectively). Additionally, mitochondria from the red portion of the semitendinosus in the low RFI line had less ROS production when succinate was used as an energ...

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Electron transport in the mitochondria is a primary source of reactive oxygen species (ROS). Excess production of ROS may lead to increased oxidative stress, decreasing nutrient utilization and efficiency. The purpose of this study was to compare mitochondrial ROS production in pigs (n = 7 per line) divergently selected for residual feed intake (RFI). Mitochondria were freshly isolated from liver by differential centrifugation. The production of H2O2 was determined by using 2, 7 ‐Dichlorofluorescein diacetate. Glutamate or succinate was provided as an energy source for complex I and II respectively. Rotenone inhibited electron backflow when using succinate. No differences in H2O2 production between the lines were observed when using glutamate as an energy substrate. When succinate was added, H2O2 production was decreased by 8% in low RFI pigs compared to their high RFI counterparts (46.7 vs. 34.3 nmol H2O2/mg protein/min ± 8.87). Other inhibitors of electron transport, 4,4,4‐trifluoro‐1‐ [2‐thienyl]‐1,3‐butanedione, malonate, or the combination of these, yielded similar results (P<0.05). Altogether, these data indicate that less efficient, high RFI, pigs are more prone to hepatic intracellular oxidative stress. This may explain why low RFI pigs are more efficient at utilizing and partitioning nutrients for growth and metabolism. This research was supported by USDA‐AFRI grant# 2010‐65206‐20670.