Abstract
ObjectivesEfficiency of pork production is critical as demand for animal protein rises with increases in global populations and income. Feed efficiency and response to disease challenge are affected by stressors that increase reactive oxygen species in muscle. Reactive oxygen species are detrimental to growth, as they require the expenditure of energy for tissue repair that could be used for weight gain. Peroxiredoxin-2 (Prdx-2) is an antioxidant enzyme that converts hydrogen peroxide to water using reactive cysteines, thus mitigating oxidation. Prdx-2 can exist in multiple oxidation states (reduced, oxidized, and hyperoxidized) and quantenary structures (dimer and decamer). Prdx-2 concentration is greater in more color stable muscles and may be an indicator of tenderness. The objective of this study was to determine differences in Prdx-2 profile and protein oxidation between pigs that differed in feed efficiency and health status. Materials and MethodsPigs selected for differing feed efficiency based on residual feed intake (RFI) were used in a 2 × 2 factorial design for this study. At 50 ± 7 kg in body weight, high RFI (less efficient) and low RFI (more efficient) barrows were distributed between 2 rooms in the same building. One room was inoculated with a dual respiratory/enteric bacterial health challenge. At 21 d post-infection (projected peak of illness), pigs were necropsied (total = 24, n = 6 per group) and longissimus muscle samples were collected. Reduced and nonreduced sarcoplasmic protein samples (β-mercaptoethanol) were used for western blot analyses. Reduced samples were used to quantify total Prdx-2, while nonreduced samples were used to evaluate hyperoxidized peroxiredoxin, Prdx-2 decamer, and Prdx-2 profile in nonreducing gels (2 distinct bands analyzed). Carbonyl content and diagonal gel electrophoresis were performed on sarcoplasmic protein samples to determine protein oxidation. Statistical analysis was performed using SAS v. 9.4 (SAS Inst. Inc., Cary, NC) with fixed effects of RFI line, infection status, and RFI line × infection status interaction. Gel repetition and necropsy day were included as random effects. ResultsInfection status was significant for the Prdx-2 band comparison in nonreducing gels (P = 0.014) indicating potential differences in posttranslational modifications. Compared to low RFI pigs, high RFI pigs had greater total Prdx-2 (P = 0.035), greater Prdx-2 decamer (P = 0.0007), greater Prdx-2 in the second band of nonreducing gels (P = 0.0006), and less hyperoxidized peroxiredoxin relative to the total immunoreactive protein (P = 0.028). An interaction existed between RFI line and infection status for the Prdx-2 band comparison (P = 0.02), with high RFI challenged pigs having greater ratios, and high RFI control pigs having lesser ratios relative to low RFI pigs. Visual analysis of diagonal gels showed more proteins with intermolecular disulfide formation in low RFI muscle samples. No significant difference was seen for carbonyl content. ConclusionDifferences exist in Prdx-2 profile based on RFI line and infection status. High and low RFI pigs may respond differently to health challenges at the molecular level based on differences in antioxidant protein response. By defining Prdx-2 in livestock muscle, we may be better able to manage animals to meet demand for meat without increasing inputs.
Highlights
The impact of disease challenges on the efficiency of meat animal production is an immensely important aspect of livestock production
Differences were seen in Prdx-2 profile based on residual feed intake (RFI) line and to a lesser extent infection status, contrary to our original hypothesis no significant differences were seen in carbonyl content based on RFI line or infection status
This may be partially explained by the increase in Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) oxidation product in MhLi pigs, high RFI MhLi pigs, potentially leading to an increase in reduced glutathione protein and prevention of more widespread protein oxidation (Kuehne et al, 2015)
Summary
The impact of disease challenges on the efficiency of meat animal production is an immensely important aspect of livestock production. Improving the efficiency of pork production is paramount as global demand for animal protein increases alongside increases in populations and incomes in the developing world. Two factors that have a significant impact on pork production are feed efficiency and response to disease challenges. Both of these factors are influenced by oxidative stress (Bottje et al, 2002; Deblanc et al, 2013; Grubbs et al, 2013; Sies et al, 2017). More in depth research is needed to improve understanding of the relationship between oxidative stress balance and related factors that impact production, such as feed efficiency and health challenge response
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