The objective of this thesis was to determine the impact of health challenge in the form of a dual respiratory and enteric bacterial health challenge on the antioxidant protein peroxiredoxin-2 (Prdx-2) and protein oxidation in the skeletal muscle of pigs selected for differing residual feed intake (RFI), a measure of feed efficiency. It was hypothesized that differences would exist in Prdx-2’s profile based on RFI line and infection status (IS) and that high RFI (less efficient) and health challenged pigs would present a higher degree of protein oxidation due to increased oxidative stress.

Barrows (50à ±7 kg, total n=24) divergently selected for RFI from the 11th generation of the ISU RFI Project were used for this study. To induce a respiratory and enteric health challenge, half of the pigs (n=6 / RFI line) were inoculated with Mycoplasma hyopneumoniae (Mh) and Lawsonia intracellularis (Li) on 0 days post infection (dpi). Uninoculated pigs in a separate room served as controls (n=6 / RFI line). Pig ADG, ADFI, and G: F were calculated during a 21 day acclimation period (dpi -21 to dpi 0) and from inoculation to projected peak infection (dpi 0 to dpi 21). At dpi 21 all pigs were necropsied, and longissimus skeletal muscle samples were immediately collected for analysis. Protein oxidation, various forms of Prdx-2, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) content was measured on longissimus skeletal muscle sarcoplasmic protein.

No significant differences were seen in protein carbonylation, but low RFI pigs showed an increase in disulfide bound creatine kinase and GAPDH in the sarcoplasmic protein of the longissimus skeletal muscle. Further analysis showed MhLi pigs had a greater amount of oxidized GAPDH (P=0.017). Significant differences were seen based on both RFI line and infection status for non-reducing gel Prdx-2 suggesting differences in some posttranslational modifications. There was an increase in total Prdx-2 (P=0.035) and Prdx-2 decamer (P=0.0007) in high RFI pigs while hyperoxidized peroxiredoxin relative to Prdx-2 was increased in low RFI pigs (P=0.028).

Pigs divergently selected for RFI may differ in antioxidant protein profile and oxidative stress response. High RFI pigs’ reduced efficiency appears to be the result of increased Prdx-2 production, resulting greater pool of reduced Prdx-2 to combat oxidative stress challenges.