Changes in the Protein Profile of Porcine Liver in Response to Immune System Stimulation

Immune system function has a direct influence on swine growth. Using lipopolysaccharide (LPS) to stimulate the immune system of pigs provides insight on how they handle immunological stress. Several proteins were shown to be part of the liver’s response to LPS. These proteins included heat shock protein (HSP) 60, HSP70, and peroxiredoxin-2. Changes in the abundance of these proteins indicate the extent to which an animal can respond to this immune system stimulation (ISS). Proteins responsible for cellular rescue were found to be increased in abundance in pigs with stimulated immune systems

Degradation of Filamin in Aged Pork Loins Classified by High and Low Star Probe Values

Filamin is necessary to maintain the integrity of muscle structure. Postmortem degradation of filamin results in loss of organizational structure at the Z-disk and improves meat tenderness. Intact and degraded filamin was successfully identified in aged pork loin. The removal of amino acids to form this degradation product is likely the first cleavage of intact filamin observed in postmortem muscle. A significant decrease in abundance of intact filamin in low star probe (SP) value samples demonstrates that degradation of filamin varies when aging period and pH are similar. Filamin degradation was significantly different in SP groups, suggesting that filamin proteolysis and formation of degradation products may have an impact on the SP values of aged pork loin

Proteolysis Influences Tenderness of Aged Pork Loins

Aged pork loins were selected to have similar ultimate pH, color, lipid content, and purge. The star probe values (kg) obtained from these loins were evaluated and loins were sorted into either a low star probe (LSP) group or a high star probe (HSP) group. Loins were evaluated for autolysis of calpain-1 and degradation of troponin-T, desmin, and titin. Results showed calpain-1 was completely autolyzed in all samples. LSP pork loins exhibited more degradation of troponin-T, desmin, and titin, demonstrating proteolysis influences measured tenderness in aged pork

Contribution of Early-Postmortem Proteome and Metabolome to Ultimate pH and Pork Quality

This study's objectives were to identify how subtle differences in ultimate pH relate to differences in pork quality and to understand how early-postmortem glycolysis contributes to variation in ultimate pH. The hypothesis was that elements in early-postmortem longissimus thoracis et lumborum proteome and metabolome could be used to predict quality defects associated with pH decline. Temperature and pH of the longissimus thoracis et lumborum were measured at 45 min, 24 h, and 14 d postmortem. Quality measurements were made after 14 d of aging. Groups were classified as normal pH (NpH; x̄ = 5 . 59 [5.53–5.67]; NpH, n = 10) and low pH (LpH; x̄ = 5 . 42 [5.38–5.45]; LpH, n = 10) at 14 d postmortem. Metabolites from 45 min postmortem were identified using GC-MS. Relative differences between proteins were quantified with two-dimensional difference in gel electrophoreses, and spots were identified with MALDI-MS. Western blot analyses were used to measure phosphofructokinase, peroxiredoxin-2, and reduced and non-reduced adenosine monophosphate deaminase-2 at 45 min and 14 d postmortem. Ultimate pH classification did not affect 45-min-postmortem pH (P = 0.64); 14-d pH was different between groups (P < 0.01). NpH had less purge loss (P < 0.01), was darker (P < 0.01), had lower star probe (P < 0.01), and had less intact day-7 desmin (P = 0.02). More pyruvate (P = 0.01) and less lactate (P = 0.09) was observed in NpH, along with more soluble lactate dehydrogenase (P = 0.03) and pyruvate kinase (P < 0.10). These observations indicate that differences in enzyme abundance or solubility may produce more pyruvate and less lactate. Fructose 6-phosphate was more abundant (P = 0.08) in the LpH group, indicating that phosphofructokinase may be involved in glycolytic differences. Furthermore, greater abundance of heat shock proteins, peroxiredoxin-2 (P = 0.02), and malate (P = 0.01) early postmortem all suggest differences in mitochondrial function and oxidative stability that contribute to quality differences. These results show that even subtle changes in ultimate pH can influence pork quality. The proteome and metabolome at 45 min postmortem are associated with variation in the extent of pH decline

Novel Observations of Peroxiredoxin-2 Profile and Protein Oxidation in Skeletal Muscle From Pigs of Differing Residual Feed Intake and Health Status

This study’s objective was to determine the impact of a dual respiratory and enteric bacterial health challenge on the antioxidant protein peroxiredoxin-2 (Prdx-2) profile and protein oxidation in the skeletal muscle of pigs from 2 lines that were divergently selected for residual feed intake (RFI). The hypotheses were that (1) differences exist in the Prdx-2 profile between 2 RFI lines and infection status and (2) muscle from less efficient high-RFI and health-challenged pigs have greater cellular protein oxidation. Barrows (50 ± 7 kg, N = 24) from the 11th generation of the high-RFI (n = 12) and low-RFI (n = 12) Iowa State University lines were used. Pigs (n = 6 per line) were inoculated with Mycoplasma hyopneumoniae and Lawsonia intracellularis (MhLI) on day 0 post infection to induce a respiratory and enteric health challenge. Uninoculated pigs served as controls (n = 6 per line). Necropsy was at 21 d post infection. Sarcoplasmic protein oxidation, various forms of Prdx-2, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) content were determined. Neither RFI line nor infection status significantly affected protein carbonylation. Under nonreducing conditions, MhLI pigs had a greater amount of a slower-migrating GAPDH band (P = 0.017), indicating oxidative modification. Regardless of health status, the low-RFI pigs had less total Prdx-2 (P = 0.035), Prdx-2 decamer (P = 0.0007), and a higher ratio of hyperoxidized peroxiredoxin relative to Prdx-2 (P = 0.028) than the high-RFI pigs. The increased pool of active Prdx-2 in high-RFI pigs suggests greater oxidative stress in muscle in high- versus low-RFI pigs. The increase in oxidized GAPDH seen in muscle from MhLI pigs—particularly the high-RFI MhLI pigs—may be a response to the greater oxidative stress in the high-RFI MhLI. This work suggests that antioxidant proteins are important in growth and health-challenge situations

Influence of postmortem aging and post-aging freezing on pork loin quality attributes

The objectives were to determine 1) the interaction between aging duration and post-aging freezing on pork loin quality attributes and 2) the relationship between pork loin star probe (SP) and Warner-Bratzler shear force (WBS). Loins from 20 carcasses were collected 1 d postmortem. Chops (n = 9; 2.54-cm thick) were fabricated from each loin and vacuum packaged. Four chops from each loin were aged at 4°C for 1, 8, 14, and 21 d and immediately evaluated (Fresh). Four adjacent chops were aged (1, 8, 14, and 21 d), frozen for 14 d, and thawed for evaluation (Frozen). An additional chop was used for evaluation of sarcomere length, intact desmin, and troponin-T degradation. Purge, objective color, pH, subjective color and marbling score, cook loss, SP, and WBS were evaluated at each aging period. Desmin and troponin-T degradation, and sarcomere length were measured on fresh samples at each day of aging. Post-aging freezing had no significant impact on SP, WBS, pH, and subjective color or marbling score at any aging period. Fresh chop purge increased at each day of aging (P 0.05). Aging, without freezing, for 14 or 21 d did not improve SP or WBS observed at 8 d, corresponding with changes in desmin degradation

Effect of a dual enteric and respiratory pathogen challenge on swine growth efficiency, carcass composition, and pork quality

The objective of this study was to determine the influence a dual respiratory and enteric pathogen challenge on growth performance, carcass composition, and pork quality of high and low feed efficient pigs. It was hypothesized that pigs with greater feed efficiency would have a more negative response to an early growth period dual pathogen challenge than less feed efficient pigs. Pigs divergently selected for low and high residual feed intake (RFI, ~ 68 kg) from the 11th generation of Iowa State University RFI project were used to represent high and low feed efficiency. To elicit a dual pathogen challenge, half of the pigs (n = 12 / line) were inoculated with Mycoplasma hyopneumoniae (Mh) and Lawsonia intracellularis (MhLI) on days post inoculation (dpi) 0. Pigs in a separate room of the barn were not inoculated and were used as controls (n = 12 / RFI line). Pigs were weighed and feed intake was recorded to calculate ADG, ADFI, and G:F for the acclimation period (period 1: dpi -21 - 0), during peak infection (period 2: dpi 0 - 42), and during the remaining growth period to reach market weight (period 3: dpi 42 – slaughter). At ~ 125 kg, pigs were slaughtered using standard commercial procedures. Carcasses were evaluated for composition (weight, fat free lean, loin eye area, 10th rib fat depth) and meat quality (pH decline, temperature decline, Hunter L, a, and b, subjective color and marbling, star probe, drip loss, cook loss, proximate composition, and desmin degradation). Challenged pigs had reduced ADFI during period 2 (P 0.05). Loin chops from the less feed efficient, high RFI pigs, had greater drip loss, greater cook loss, lesser % moisture, greater Hunter L values, and greater Hunter b values (P 0.05). Peak antibody response of Mh was correlated significantly with pH decline, temperature decline, color (Hunter L, a, and b), drip loss, cook loss, 10th rib back fat, % moisture, and % fat (P < 0.05). These results indicate that a MhLI challenge early in growth did not significantly impact ultimate carcass composition or meat quality traits. Further, selection for greater feed efficiency in pigs did not affect their response to pathogenic challenge. The antibody response correlations are indicative of a previously unrecognized relationship between a dual pathogen challenge early in growth and carcass composition and pork quality.</p

Changes in the Protein Profile of Porcine Liver in Response to Immune System Stimulation

Immune system function has a direct influence on swine growth. Using lipopolysaccharide (LPS) to stimulate the immune system of pigs provides insight on how they handle immunological stress. Several proteins were shown to be part of the liver’s response to LPS. These proteins included heat shock protein (HSP) 60, HSP70, and peroxiredoxin-2. Changes in the abundance of these proteins indicate the extent to which an animal can respond to this immune system stimulation (ISS). Proteins responsible for cellular rescue were found to be increased in abundance in pigs with stimulated immune systems.</p

Degradation of Filamin in Aged Pork Loins Classified by High and Low Star Probe Values

Filamin is necessary to maintain the integrity of muscle structure. Postmortem degradation of filamin results in loss of organizational structure at the Z-disk and improves meat tenderness. Intact and degraded filamin was successfully identified in aged pork loin. The removal of amino acids to form this degradation product is likely the first cleavage of intact filamin observed in postmortem muscle. A significant decrease in abundance of intact filamin in low star probe (SP) value samples demonstrates that degradation of filamin varies when aging period and pH are similar. Filamin degradation was significantly different in SP groups, suggesting that filamin proteolysis and formation of degradation products may have an impact on the SP values of aged pork loin.</p

Proteolysis Influences Tenderness of Aged Pork Loins

Aged pork loins were selected to have similar ultimate pH, color, lipid content, and purge. The star probe values (kg) obtained from these loins were evaluated and loins were sorted into either a low star probe (LSP) group or a high star probe (HSP) group. Loins were evaluated for autolysis of calpain-1 and degradation of troponin-T, desmin, and titin. Results showed calpain-1 was completely autolyzed in all samples. LSP pork loins exhibited more degradation of troponin-T, desmin, and titin, demonstrating proteolysis influences measured tenderness in aged pork.</p