Characterizing membrane phospholipid hydrolysis of pork loins throughout three aging periods.

Three chops from 20 pork carcasses were aged for 1, 8, and 21 days. Electrospray ionization-tandem mass spectrometry was used to comprehensively analyze profiles of phospholipids from each sample (n = 60). Total phospholipid quantity decreased 4-folds (P < .01) from 1 to 21 days of aging in pork loins. Phosphatidylinositol (PI) and phosphatidylserine (PS) increased by 30% and 73%, respectively, from 1 to 21 days of aging in pork loins (P < .01). This increase was mainly due to relative percentage increase from PI 38:4 (18:0-20:4) and PS 36:2 (18:0-18:2; P < .01). The results also showed that the relative percentage of lysophosphatidylcholine increased by 35% after short term aging (8d), and phosphatidic acid increased by 10-folds after extended aging (21d; P < .01). These results documented that phospholipids undergo enzymatic hydrolysis during aging, but also indicated that lipid species containing 18:2 or 20:4 within PI and PS were slightly more resistant to enzymatic hydrolysis compared with the other phospholipids.

Predicting aged pork quality using a portable Raman device.

The utility of Raman spectroscopic signatures of fresh pork loin (1 d & 15 d postmortem) in predicting fresh pork tenderness and slice shear force (SSF) was determined. Partial least square models showed that sensory tenderness and SSF are weakly correlated (R2 = 0.2). Raman spectral data were collected in 6 s using a portable Raman spectrometer (RS). A PLS regression model was developed to predict quantitatively the tenderness scores and SSF values from Raman spectral data, with very limited success. It was discovered that the prediction accuracies for day 15 post mortem samples are significantly greater than that for day 1 postmortem samples. Classification models were developed to predict tenderness at two ends of sensory quality as "poor" vs. "good". The accuracies of classification into different quality categories (1st to 4th percentile) are also greater for the day 15 postmortem samples for sensory tenderness (93.5% vs 76.3%) and SSF (92.8% vs 76.1%). RS has the potential to become a rapid on-line screening tool for the pork producers to quickly select meats with superior quality and/or cull poor quality to meet market demand/expectations.

Effects of heat stress and insulin sensitizers on pig adipose tissue.

Heat stress (HS) negatively impacts several swine production variables, including carcass fat quality and quantity. Pigs reared in HS have more adipose tissue than energetically predicted, explainable, in part, by HS-induced hyperinsulinemia. Study objectives were to evaluate insulin's role in altering fat characteristics during HS via feeding insulin-sensitizing compounds. Forty crossbred barrows (113 ± 9 kg BW) were randomly assigned to one of five environment by diet treatments: 1) thermoneutral (TN) fed ad libitum (TNAL), 2) TN and pair-fed (TNPF), 3) HS fed ad libitum (HSAL), 4) HS fed ad libitum with sterculic oil (SO) supplementation (HSSO; 13 g/d), and 5) HS fed ad libitum with dietary chromium (Cr) supplementation (HSCr; 0.5 mg/d; Kemin Industries, Des Moines, IA). The study consisted of three experimental periods (P). During P0 (2 d), all pigs were exposed to TN conditions (23 ± 3 °C, 68 ± 10% RH) and fed ad libitum. During P1 (7 d), all pigs received their respective dietary supplements, were maintained in TN conditions, and fed ad libitum. During P2 (21 d), HSAL, HSSO, and HSCr pigs were fed ad libitum and exposed to cyclical HS conditions (28 to 33 °C, 58 ± 10% RH). The TNAL and TNPF pigs remained in TN conditions and were fed ad libitum or pair-fed to their HSAL counterparts. Rectal temperature (TR), respiration rate (RR), and skin temperature (TS) were obtained daily at 0600 and 1800 h. At 1800 h, HS exposed pigs had increased TR, RR, and TS relative to TNAL controls (1.13 °C, 48 bpm, and 3.51 °C, respectively; P < 0.01). During wk 2 and 3 of P2, HSSO pigs had increased 1800 h TR relative to HSAL and HSCr (~0.40 and ~0.42 °C, respectively; P ≤ 0.05). Heat stress decreased ADFI and ADG compared to TNAL pigs (2.24 vs. 3.28 and 0.63 vs. 1.09 kg/d, respectively; P < 0.01) and neither variable was affected by SO or Cr supplementation. Heat stress increased or tended to increase moisture content of abdominal (7.7 vs. 5.9%; P = 0.07) and inner s.c. (11.4 vs. 9.8%; P < 0.05) adipose depots compared to TNAL controls. Interestingly, TNPF pigs also had increased adipose tissue moisture content and this was most pronounced in the outer s.c. depot (15.0 vs. 12.2%; P < 0.01) compared to TNAL pigs. Heat stress had little or no effect on fatty acid composition of abdominal, inner, and outer s.c. adipose tissue depots. In summary, the negative effects of HS on fat quality do not appear to be fatty acid composition related, but may be explained by increased adipose tissue moisture content.

Porcine epidemic diarrhea virus reduces feed efficiency in nursery pigs.

Porcine epidemic diarrhea virus (PEDV) infects enterocytes and in nursery pigs, results in diarrhea, anorexia, and reduced performance. Therefore, the objective of this study was to determine how PEDV infection influenced growth performance and repartitioning of amino acids and energy in nursery pigs. A total of 32 barrows and gilts, approximately 1 wk post-wean (BW = 8.46 ± 0.50 kg), and naïve for PEDV were obtained, weighed, and allotted based on sex and BW to one of two treatments: 1) Control, PEDV naïve and 2) PEDV-inoculated (PEDV) with eight pens of two pigs each per treatment. On day post-inoculation (dpi) 0, PEDV pigs were inoculated via intragastric gavage with PEDV isolate (USA/Iowa/18984/2013). Pig and feeder weights were recorded at dpi -7, 0, 5, and 20 in order to calculate ADG, ADFI, and G:F. Eight pigs per treatment were euthanized on dpi 5 and 20, and tissues and blood were collected. At dpi 5, all PEDV pigs were PCR positive for PEDV in feces. Overall, PEDV pigs tended (P < 0.10) to increase ADFI, which resulted in reduced (P < 0.05) feed efficiency. At dpi 5, PEDV pigs had reduced (P < 0.05) villus height and increased (P < 0.05) stem cell proliferation in the jejunum compared with Control pigs. Pigs inoculated with PEDV had increased (P < 0.05) serum haptoglobin and increased insulin-to-glucose ratios compared with Control pigs at dpi 5. Markers of muscle proteolysis were not different (P > 0.05) between treatments within dpi; however, at dpi 5, 20S proteasome activity was increased (P < 0.05) in longissimus dorsi of PEDV pigs compared with Control pigs. Liver and jejunum gluconeogenic enzyme activities were not different (P > 0.05) between treatments within dpi. Overall, PEDV-inoculated pigs did recover the absorptive capacity that was reduced during PEDV infection by increasing proliferation of intestinal stem cells. However, the energy and nutrients needed to recover the epithelium may be originating from available luminal nutrients instead of muscle proteolysis and gluconeogenesis. This study provides insight into the effects of an enteric coronavirus on postabsorptive metabolism in nursery pigs.

Temporal proteomic response to acute heat stress in the porcine muscle sarcoplasm.

Heat stress (HS) is an important topic in the swine industry, costing hundreds of millions of dollars in economic losses annually, figures that could easily rise in light of global climate change. Muscle biology during HS is particularly important given skeletal muscle's large proportion to the body and its ultimate conversion to meat. Here we report the proteomic changes that occur during acute HS (37°C and 40% relative humidity) lasting 2, 4, or 6 h in the muscle sarcoplasm of growing pigs in comparison with 6 h of thermal neutral (TN; 21°C and 70% relative humidity) conditions ( = 8 per treatment). The red and white areas of the semitendinosus muscle were used to compare the differential effects of HS on oxidative or glycolytic muscles. The results support the hypothesis of proteomic profile differences between the acute HS and TN groups. Altered abundance ( < 0.05) of several proteins occurred in as little as 2 h of HS, affecting metabolism, cell structure, and chaperone, antioxidant, and proteolytic activity. We determined that the muscle HS response is both fiber type and time specific. Overall, more differences were observed in the red semitendinosus than in the white semitendinosus, although the time point at which differences were observed varied. These data show that as little as 2 h of HS has measurable effects on muscle proteins, indicating that acute HS has the potential to impair muscle function and growth.

Proteomic features linked to tenderness of aged pork loins.

There is considerable evidence that the protein component of fresh pork makes a major contribution to tenderness. In particular, the proteomic profile can be linked to postmortem events including pH decline, tissue oxidation, and protein degradation. The objectives for this study were to determine differences in sarcoplasmic proteomes that contribute to tenderness variation in aged pork longissimus dorsi muscles (LM). A defined set of pork loins selected to be similar in pH, color, and lipid yet different in tenderness were used. Pork loins were assigned to tenderness groups based on their star probe values; a high star probe group (HSP; n=12 mean star probe 7.75 kg) and low star probe group (LPS; n=12 star probe 4.95 kg) Samples were selected for proteomic experiments based on star probe values, and selected samples were within specified ranges for ultimate pH (5.54-5.86), marbling score (1.0-3.0), and percent total lipid (1.61-3.37%). Two-dimensional difference in gel electrophoresis (2D-DIGE) and mass spectrometry were used to examine sarcoplasmic protein abundance and potential modifications. Proteins spots that were significantly different across groups were selected for identification. Results from 2D-DIGE showed that HSP samples had significantly more abundant metabolic, stress response, and regulatory proteins in the sarcoplasmic fraction compared with LSP samples. The stress response protein peroxiredoxin-2 was more abundant in HSP samples as determined by 2D-DIGE ( ≤ 0.01; 2 spots) and western blot assay ( = 0.02). Low star probe samples showed significantly more degradation of the structural protein desmin in 2D-DIGE ( < 0.01) and western blot assay ( < 0.01). These results demonstrate that extreme proteolytic differences influenced measured tenderness of LSP and HSP samples and that soluble desmin and peroxiredoxin-2 may be used as biomarkers to differentiate between tough and tender aged pork products.

Influence of feed efficiency classification and growing and finishing diet type on meat tenderness attributes of beef steers.

Enhancing feed efficiency (FE) in cattle continues to be an important goal in the beef industry. Previous research suggests improving FE may alter calpain system activity, potentially having negative effects on meat tenderness. The objective of this study was to assess the potential influence of beef cattle FE on postmortem meat tenderness. During the growing phase, 181 crossbred steers were fed for 76 d at the University of Missouri on a whole shell corn-based diet (MU-Corn; = 90) or a roughage-based diet (MU-Rough; = 91). Within diet, steers were classified for FE based on residual feed intake (RFI) calculations. Within each growing phase diet, the 12 most feed efficient (HFE; average RFI -3.33 ± 0.77) and 12 least feed efficient (LFE; average RFI 2.90 ± 0.94) steers (48 steers total) were selected and shipped to Iowa State University for the finishing phase. Steers were fed in pens with GrowSafe bunks and equally assigned to a cracked corn-based finishing diet (ISU-Corn) or a byproduct-based finishing diet (ISU-Byp) for the 87-d finishing phase. After a 24-h chill, rib sections were collected from all carcasses and aged for 2 or 14 d prior to analysis of calpastatin activity and calpain 1 autolysis (d 2), troponin-T degradation (d 2 and 14), proximate composition (d 2), and Warner-Bratzler shear force (WBSF; d 14). Data were analyzed as a 2 × 2 × 2 factorial, with steer or steak as the experimental unit ( = 6 per treatment combination). There were no 3- or 2-way interactions ( ≥ 0.12) noted for any data, with the exception of steak lipid content, which tended ( = 0.08) to be affected by FE × Iowa State University diet. Steaks from LFE steers had greater lipid content compared with steaks from HFE steers within ISU-Byp, with no differences due to FE within ISU-Corn. Growing diet did not affect calpastatin activity, calpain 1 autolysis, or troponin T degradation ( ≥ 0.12); however, MU-Rough had greater WBSF than MU-Corn ( = 0.05). Day-2 calpastatin activity tended ( = 0.10) to be greater in steaks from HFE vs. LFE steers, although no differences due to FE classification were observed for calpain 1 protein, troponin-T degradation, or WBSF ( ≥ 0.13). Finishing diet did not affect calpastatin activity, calpain 1 autolysis, d-2 troponin-T degradation, or WBSF ( ≥ 0.24); however, d-14 troponin-T degradation was greater in ISU-Corn than in ISU-Byp ( = 0.005). In this study, using phenotypic extremes for FE revealed a tendency for greater calpastatin activity only in highly feed-efficient steers; however, these data indicate that high-fiber diets may negatively impact meat tenderness, and further work is needed to clarify the influence of diet type on parameters of meat tenderness.

Postmortem protein degradation is a key contributor to fresh pork loin tenderness.

The objective of this study was to determine factors that influence tenderness independent of variation in pH, color, or marbling. To achieve the objective, 2 sample groups were chosen from a population of 159 pork loins aged 11 to 16 d. Predetermined ranges (ultimate pH, 5.54 to 5.86; marbling score, 1.0 to 3.0; percent total lipid, 1.61 to 3.37%) were defined for inclusion of individual loins in the study. The pork loins with the greatest ( = 12) and least ( = 12) Instron star probe values were assigned to 2 classification groups. The high star probe group had an average star probe that was 2.8 kg greater than the low star probe group (7.75 vs. 4.95 kg). Pork quality and sensory characteristics of pH, subjective and instrumental color values, cook loss, sensory tenderness, chewiness, juiciness, pork flavor, and off flavor were determined on fresh, never frozen pork chops. Lipid content, sarcomere length, myosin heavy-chain profile, and calpain autolysis were determined. Degradation of troponin-T, desmin, filamin, and titin were evaluated on the protein extracts from each sample. Pork loin pH, subjective color scores, Minolta L values, sarcomere length, and myosin heavy-chain composition were not different across groups. Chops from the low star probe group had a significantly greater marbling score (2.3 vs. 1.9) and lipid content (2.61 vs. 2.23%). Calpain-1 was completely autolyzed in both high and low star probe samples, demonstrating that calpain-1 potentially had been active in all samples. Low star probe whole-muscle protein extracts had more troponin-T ( < 0.01), desmin ( < 0.01), and filamin degradation ( < 0.01) than high star probe samples. Both classification groups showed degradation of titin. Remarkably, some high star probe samples still had observable intact bands of titin on SDS-PAGE gels. These results demonstrate that significant variation in instrumental tenderness is observed within a moderate pH range. Lipid content and proteolysis both appear to contribute to this variation.

A systematic review and meta-analysis of tenderness metrics in control groups used in comparative nutrition experiments.

This review reports the pork quality attributes, Warner-Bratzler Shear Force, Slice Shear Force, Star Probe, pH, marbling, color (Minolta L*/L or Hunter L*/L), and sensory tenderness evaluation, in control groups used in comparative nutrition experiments over the past 20 yr. The original aim of this study was to evaluate if changes in pork quality based on the above metrics occurred over time. To address this question, it was anticipated that data may come from 3 sources with decreasing relevance: representative retail pork surveys, representative post-harvest carcass surveys, and control groups from comparative nutrition experiments. To identify the study population, a review of studies reported in Centre for Agricultural Biosciences International Abstracts (Web of Knowledge; 1994-2014) was conducted. Two national level surveys of retail pork and 146 relevant nutritional experiments studies, with 228 control groups, were identified by the search. It was not possible to conduct a meta-analysis of the retail pork surveys based on only 2 time points. For the comparative studies, a random effects meta-analysis was conducted with year as a covariate to assess the impact of time on the outcome. In the absence of modifiers, there was no evidence of meaningful change in the mean Warner-Bratzler Shear Force, pH, color, marbling, or sensory scores over the study period. There was evidence of substantial between-study heterogeneity in the characteristics of control pigs used over the years for Warner-Bratzler Shear Force and measures of color. The absence of publicly-available representative surveys of pork quality meant the changes in pork quality over time were not clear. If changes in pork quality have occurred, the data suggest that pigs used as controls in experiments may have become less representative of commercial pigs over time and the translatability of study findings from nutrition experiments might be reduced over time. Alternately, if commercial pigs have not changed, then control pigs reflect this. The study does not address if control groups in other experimental intervention studies had similar tenderness patterns as reported here for nutritional interventions. A large amount of potentially available data was excluded from the analysis due to incomplete reporting in the original study reports.

Identification of potential serum biomarkers to predict feed efficiency in young pigs.

Identification of biomarkers for feed efficiency in livestock will aid in the efficient production of high-quality protein to meet the demands of a growing population. The overall objective of this research was to identify biomarkers in serum for swine feed efficiency and to discover pathways affected by divergent selection for residual feed intake (RFI). Serum was collected from young pigs (between 35 and 42 d of age) from 2 lines of pigs that have been genetically selected to be either more efficient (low-RFI) or less efficient (high-RFI). After blood collection, during finishing, pigs from each line were placed on either a low-energy/high-fiber diet or a traditional high-energy/low-fiber diet to test for any diet effects on RFI. Subsets of 6 pigs per line within each diet were used in 3 independent experiments. Pigs with extreme RFI phenotypes from the low-energy/high-fiber diet were used to confirm the results from the first 2 comparisons. Two-dimensional difference in gel electrophoresis and mass spectrometry were used to identify proteins with different abundances between RFI line or finishing diet. Three proteins had consistent and significant ( < 0.05) RFI line differences for both diets: gelsolin, vitronectin, and serine protease inhibitor A3 (serpinA3). Abundance of gelsolin, a protein with roles in actin filament assembly and immune response, was greater in the more efficient low-RFI pigs (9 to 39%). Vitronectin was also more abundant in the low-RFI pigs (39 to 56%) and has known roles in blood homeostasis and may regulate adiposity. SerpinA3 is a member of a very large family of proteins referred to as serine protease inhibitors. A total of 14 spots that were more abundant in the low-RFI line, some at least twice as abundant, were identified as serpinA3. Multiple isoforms of serpinA3 have been reported (serpinA3-1 to serpinA3-4 in pigs and serpinA3-1 to serpinA3-8 in cattle) with serpinA3 having many different functions dependent on isoform. Gelsolin, vitronectin, and serpinA3 are 3 proteins that may play direct and important biological roles in the pathways that control RFI and, ultimately, feed efficiency through energy utilization and homeostasis. These data demonstrate that serum proteins can be a useful source of potential biomarkers for feed efficiency and provide information on pathways with distinct expression patterns between animals that differ in feed efficiency.

Proteomic changes to the sarcoplasmic fraction of predominantly red or white muscle following acute heat stress.

UNLABELLED: Acute heat stress negatively impacts both human health and livestock production. In order to characterize the skeletal muscle cellular response to acute heat stress, the muscle sarcoplasmic proteome was analyzed via 2-D DIGE. Pigs (n=8 per treatment) were exposed to one of the three treatments for 12 h: heat stress (HS; 37 °C), thermal neutral (TN; 21°C), or TN while pair-fed (PFTN; 21 °C, feed limited based on HS group consumption). After euthanasia, the semitendinosus muscle was excised, separated into predominately red (RST) and white (WST) fiber type portions, and sarcoplasmic proteins were extracted. Spots determined in 2D-DIGE to be different due to HS were identified using ESI-MS or LC-MS/MS. Several proteins involved in glycolysis, glycogenesis, and glycogenolysis were increased or modified, indicating enhanced glycolytic capacity in response to HS. In the WST, HS decreased abundance of tubulins and soluble actin and increased phosphorylated cofilin 2 abundance, indicating a loss of microtubule structure and a likely increase in stable actin microfilaments. HS increased manganese superoxide dismutase abundance, but decreased peroxiredoxin 2 abundance, indicating an antioxidant response to HS. The proteomic response to HS suggests marked cellular changes in carbohydrate metabolism, structure, and antioxidant machinery in skeletal muscle. SIGNIFICANCE: This paper examines the proteome response of skeletal muscle to acute (short duration, high intensity) heat stress (HS). Defining changes in the sarcoplasm proteome increases our understanding of the mechanisms of how muscle responds to HS. Moreover, demonstration of a fiber type differential response to HS illustrates the dynamic nature of muscle. The experimental design of the experiment allows for the differentiation between the true effects of HS and HS-induced hypophagia. Data such as these will provide the foundation for developing future mitigating solutions and preventative therapies to reduce the detrimental effects of acute heat stress on muscle function and metabolism.

Investigation of the efficacy of albumin removal procedures on porcine serum proteome profile.

Improving the ability to predict livestock performance using biomarkers will provide a benefit for livestock genetic evaluation and improvement. The most practical biological sample to screen for development of biomarkers is serum due to the ease of collection. However, protein profiles in serum are complex and dynamic. Strategies are needed to manage variation in serum proteins used for biomarker identification. Albumin is the most abundant protein in serum, comprising over 50% of the overall protein content, and has historically been depleted from serum before biomarker identification. The objective of this study was to investigate the use of gel-based proteomic techniques to evaluate the need for porcine albumin depletion in biomarker identification. Albumin is known to bind many proteins in the blood, thus potential biomarkers could be removed during albumin depletion. Using two-dimensional difference in gel electrophoresis (2D-DIGE), we show whole serum can be used for biomarker discovery. The data obtained show that albumin removal methods are effective for porcine sera. Over 85% of the protein spots resolved on at least half of the gels were changed in abundance between whole and albumin depleted sera. Of the 204 protein spots significantly altered in abundance, 59 were changed over 400%. However, albumin removal also altered the serum proteome in an unpredictable manner; in the depleted sera, 86 protein spots were increased in abundance and 118 were decreased. Furthermore, the abundance of 59.4% of the protein spots in the albumin depleted samples had a larger standard error than whole sera. However, the resolution of albumin in 2D-DIGE analysis of whole sera permitted the detection and quantification of substantial numbers of proteins. Thus, it is proposed that whole serum can be used in a gel-based proteomics system for the identification of porcine biomarkers.

Impact of supplementing vitamin C for 56, 90, or 127 days on growth performance and carcass characteristics of steers fed a 0.31 or 0.59% sulfur diet.

The objective was to examine differential timing of vitamin C (VC) supplementation during the finishing period (for the first 56, 90, or 127 d) on performance, VC, and glutathione (GSH) concentrations and carcass traits of steers receiving a 0.31 or 0.59% S diet. Angus steers (n = 42) were stratified to pens by initial BW (304 ± 13 kg) and GeneMax marbling score (4.3 ± 0.12), and pens were randomly assigned to 1 of 7 treatments (6 steers/pen and 1 pen/treatment), including a high-S (HS; 0.59% S) control (HS CON), HS CON + 10 g VC∙steer(-1)∙d(-1) for the first 56 d of the finishing period, HS CON + 10 g VC∙steer(-1)∙d(-1) for the first 90 d of the finishing period, HS CON + 10 g VC∙steer(-1)∙d(-1) for the entire 127-d finishing period (HS VC127), low-S (LS; 0.31% S) diet + 10 g VC∙steer(-1)∙d(-1) for the first 56 d of the finishing period (LS VC56), LS diet + 10 g VC∙steer(-1)∙d(-1) for the first 90 d of the finishing period, or LS diet + 10 g VC∙steer(-1)∙d(-1) for the entire 127-d finishing period. Jugular blood and ultrasound measures were taken from all steers before feeding on d 0, 56, 90, and 127, and liver biopsies and ruminal hydrogen sulfide measurements were collected on d 121 or 122. Steers (n = 40) were harvested on d 127, and carcass data were collected. Data were analyzed by ANOVA as a completely randomized design with the fixed effect of treatment. Because individual intake data were collected, steer was the experimental unit. Final BW and ADG were greater (P ≤ 0.03) and DMI tended (P = 0.09) to be greater in the LS steers compared to HS steers, but G:F did not differ (P = 0.41) by treatment. A treatment × time effect (P = 0.04) for DMI was noted, likely due to lesser DMI between d 91 and 127 for all treatments except the HS VC127 and LS VC56. Plasma VC concentrations of LS steers were less (P = 0.05) than the HS steers. Total (P = 0.06) and reduced (P = 0.03) plasma GSH were greater in HS steers supplemented with VC than the HS CON, but liver GSH were not different due to S or VC (P ≥ 0.13). The ratio of oxidized to reduced liver GSH was greater (P < 0.01) in HS CON than HS steers supplemented with VC. Marbling score, LM area, KPH, and quality grade were not different (P ≥ 0.19) due to diet, but LS steers had greater (P = 0.05) back fat than HS steers. In conclusion, steers fed a HS diet had poorer live performance and unexpectedly greater plasma ascorbate concentrations than the LS-fed steers. Interestingly, increasing days of VC supplementation across the HS diets increased GSH indices, suggesting that although HS diets may negatively affect antioxidant capacity of cattle, supplementing VC may help correct this.

Composition and quality characteristics of carcasses from pigs divergently selected for residual feed intake on high- or low-energy diets.

The objective was to determine the extent to which feeding low-energy, high-fiber (LEHF) and high-energy, low-fiber (HELF) diets impacts meat quality and carcass composition of pigs divergently selected for residual feed intake (RFI). Two experiments were conducted in the divergently selected Iowa State University RFI lines: Exp. 1 evaluated carcasses of generation (G) 8 pigs fed on commercial feeders; Exp. 2 evaluated composition, pork quality, sensory, and postmortem proteolysis of pigs fed on electronic single-space feeders in G 8 and 9. Pigs (N = 177) in Exp. 1 were randomly assigned a pen (mixed sex and line; N = 8). Groups (n = 3) of pigs were slaughtered at a mean BW of 121.5 kg. Pigs in Exp. 2 (G8: n = 158; G9: n = 157) were randomly assigned to 1 of 6 pens of each diet per G. Pigs from G8 were slaughtered at a mean BW of 122.5 kg and G9 at a mean of 128.4 kg. Data were analyzed using the mixed procedure of SAS. Fixed effects were line, diet, sex, and all appropriate interactions. Random effects were group, pen, litter, and sire and covariate of off-test BW. For Exp. 2, G was added as a fixed effect and sensory day was added as a random effect when applicable. In Exp. 1, carcasses from low RFI (LRFI) pigs were leaner and had less fat depth (P < 0.01). Carcasses from pigs fed the LEHF diet had a lighter HCW and greater estimated percent lean than pigs fed HELF diet (P < 0.01). In Exp. 2, LRFI pigs on the HELF diet had the greatest loin depth (P < 0.01). Chops from HRFI pigs had greater drip loss, color scores, lean tissue a*, and percent lipid and lesser percent moisture than LRFI ( P< 0.05). Chops from pigs on the LEHF diet had lesser muscle L* values and greater percent moisture than chops from pigs fed the HELF diet (P < 0.05). Chops from LRFI pigs were juicer than those from HRFI pigs (P < 0.05). Protein extracted at d 2 postmortem from LRFI pigs on the LEHF diet had a greater 38 kDa desmin degradation product than protein from LRFI pigs fed the HELF diet (P < 0.05). Day 5 postmortem extracted protein from HRFI pigs had greater 38 kDa desmin degradation product than LRFI (P = 0.05). Pigs fed LEHF (P < 0.01) had adipose with a greater iodine value than adipose from HELF fed pigs. Pork sensory quality from pigs differentially selected for residual feed intake was not influenced by energy content of the diet the pigs were fed.

Effects of duration of vitamin C supplementation during the finishing period on postmortem protein degradation, tenderness, and meat color of the longissimus muscle of calf-fed steers consuming a 0.31 or 0.59% sulfur diet.

High-S (HS) diets have been identified as a causative agent in the development of oxidative stress in cattle, which in postmortem muscle can negatively alter meat quality. Vitamin C (VC) is a potent antioxidant produced endogenously by cattle; however, exogenous supplementation of VC may be useful when HS diets are fed to cattle. The objective of this study was to examine the impact of duration of VC supplementation, for the first 56, 90, or 127 d, during the finishing period on meat color and tenderness of the longissimus thoracis (LT) collected from calf-fed steers consuming a 0.31 or 0.59% S diet. Angus steers ( n= 42) were stratified to pens by initial BW (304 ± 13 kg) and GeneMax marbling score (4.3 ± 0.12), and each pen was randomly assigned to 1 of 7 treatments (6 steers/pen, 1 pen/treatment), including HS (0.59% S, a combination of dried distillers grains plus solubles and sodium sulfate) control (HS CON), HS CON + 10 g VC·steer·(-1)d(-1) for the first 56 d (HS VC56), 90 d (HS VC90), or 127 d (HS VC127), low S (LS; 0.31% S) + 10 g VC·steer·(-1)d(-1) for the first 56 d (LS VC56), 90 d (LS VC90), or 127 d (LS VC127). Steers were harvested (n = 40) and, after a 24-h chill, rib sections (LT) were collected. pH was determined on each rib section before division into 3 sections for determination of 1) 7-d retail display and color and Warner-Bratzler shear force (WBSF), 2) 14-d WBSF determination, and 3) protein degradation and collagen content (2 d postmortem). Data were analyzed by ANOVA as a completely randomized design, with the fixed effect of treatment. Individual feed intake was recorded, and steer was the experimental unit. The HS steers had a greater and lesser percent of the 80- and 76-kDa subunits of calpain-1 (P ≤ 0.05), respectively, and tended to have less (P = 0.08) troponin T degradation (d2), and more (P = 0.02) collagen than LS steers. Increasing days of VC supplementation decreased (P = 0.05) the percentage of the 80 kDa subunit of calpain-1 in HS steers but actually increased it in LS steers (P= 0.003). Supplementing VC, regardless of dietary S, did not affect meat collagen, WBSF, or color (P ≥ 0.12). a* and b* values were greater (P ≤ 0.05) in the LS treatments compared to the HS treatments. Increasing the days of VC supplementation to steers fed a HS diet appears to alleviate the negative effects of the HS diet on calpain-1 but has no effect on muscle tenderness or meat color.

Carcass composition of market weight pigs subjected to heat stress in utero and during finishing.

Objectives were to investigate the effects of prolonged gestational and/or postnatal heat stress on performance and carcass composition of market weight pigs. Pregnant gilts were exposed to gestational heat stress (GHS, 28°C to 34°C, diurnal) or thermal neutral (18°C to 22°C, diurnal) conditions during the entire gestation or during the first or second half of gestation. At 14 wk of age (58 ± 5 kg), barrows were housed in heat stress (32°C, HS) or thermal neutral (21°C, TN) conditions. Feed intake and BW were recorded weekly, and body temperature parameters were monitored twice weekly until slaughter (109 ± 5 kg). Organs were removed and weighed, and loin eye area (LEA) and back fat thickness (BF) were measured after carcass chilling. Carcass sides were separated into lean, separable fat, bone, and skin components and were weighed. Moisture, lipid, and protein content were determined in the LM at the 10th rib. Data were analyzed using a split plot with random effect of dam nested within gestational treatment. Carcass measurements included HCW as a covariate to control for weight. Planned orthogonal contrast statements were used to evaluate the overall effect of GHS in the first half, second half, or any part of gestation. Gestational heat stress did not alter postnatal performance or most body temperature parameters (P > 0.10). However, ADFI in the finishing period was increased (P < 0.05) in response to GHS, particularly in pigs receiving GHS in the first half of gestation. Gestational heat stress during the first half of gestation decreased head weight as a percent of BW (P = 0.02), whereas GHS in the second half of gestation decreased bone weight as a percent of BW (P = 0.02). Heat stress reduced ADG, BW, and HCW (P < 0.0001). Lean tissue was increased in HS pigs on both a weight and percentage basis (P < 0.0001), but LEA was similar to TN carcasses (P = 0.38). Carcasses from HS barrows also had less carcass separable fat (P < 0.01) and tended to have less BF (P = 0.06) compared with those from TN barrows, even after controlling for HCW. However, percent intramuscular fat did not differ between treatments (P = 0.48). The LM from HS carcasses had a greater moisture to protein ratio (P = 0.04). HS barrows also had decreased heart (P < 0.001) and kidney (P < 0.0001) as a percent of BW compared with TN pigs. In summary, GHS may affect head and bone development, subsequently affecting carcass composition. Chronic HS during finishing results in longer times to reach market weight and a leaner carcass once market weight is achieved.

Liver and skeletal muscle mitochondria proteomes are altered in pigs divergently selected for residual feed intake.

Animals selected for residual feed intake (RFI) can be used as a model to elucidate molecular explanations for differences in growth efficiency. The objective of this study was to determine the extent to which the protein profile and posttranslational modifications of mitochondria from skeletal muscle and liver relate to feed efficiency gains in pigs divergently selected for RFI. Mitochondria were isolated from the longissimus dorsi (LD) muscle and the liver from pigs (n = 9 each for the high and low RFI line; BW = 95.8 kg). Mitochondria protein profile differences were determined using two-dimensional difference in gel electrophoresis. Proteins were identified using electrospray ionization mass spectrometry. In the line comparison, the ß subunit of ATP synthase, heat shock protein (HSP) 60, and HSP70, were identified as being increased in mitochondria from the liver of the low RFI line (23 to 50%; P < 0.1). These differences were not observed in the other comparisons. In the LD, proteins identified as being different between RFI phenotypes included HSP70 and subunit 1 of the cytochrome bc1 complex. These data indicate that genetic selection for RFI tends to result in a consistent change in mitochondrial protein profile. In contrast, classification by phenotype demonstrates that phenotypic differences in RFI are not specifically associated with alterations of the mitochondria protein profile.

Calpain-1 activity in bovine muscle is primarily influenced by temperature, not pH decline.

The objectives of this study were to 1) determine the conditions (temperature and pH) that exist in early postmortem muscle of normally chilled and delay chilled beef carcasses to provide a model for in vitro work and 2) determine the mechanism by which early postmortem temperature/pH conditions found in beef muscle influence the enzymes that regulate the aging process in vitro. For objective 1, 7 finished beef animals (HCW 385 ± 8 kg) were harvested with the right sides subjected to normal chilling (2.3°C) approximately 1.25 h postmortem and the left sides subjected to ambient temperature (delay chilling; 22.6°C) for an additional 4.75 h postmortem and then allowed to chill at 2.3°C. Delay chilled carcasses had a more rapid pH decline (P < 0.05) and a slower rate of carcass cooling (P < 0.05). No differences were observed between normally chilled and delay chilled samples for sarcomere length or postmortem proteolysis of troponin T (TnT; P > 0.10). Warner-Bratzler shear force (WBSF) was reduced in steaks from normally chilled carcasses at 14 d (P < 0.05), while results indicated a strong, positive correlation between 14-d WBSF and 3-h longissimus dorsi muscle (LM) temperature (r = 0.67, P < 0.01) as well as a strong, negative correlation between 14-d WBSF and 6-h LM pH (r = -0.65, P < 0.02). These results were used to design the methodology for objective 2, where isolated myofibrils were subjected to µ-calpain digestion at 4 or 22°C with either a fast or slow initial pH decline. As expected, digestions with a fast initial pH decline had lower pH values in the early time points of the incubation (P < 0.05). No differences were detected in µ-calpain activity or in the degradation of intact TnT between the fast and slow pH decline treatments (P > 0.10); however, warmer digestions resulted in a tendency for increased activation of µ-calpain (P < 0.10) and a significant reduction in intact TnT (P < 0.05). Additionally, a temperature × time interaction was revealed in µ-calpain activity and in the degradation of intact TnT (P < 0.05). Specifically, assayed calpain activity was lower at 0.17, 0.33, 1, and 3 h and greater at 72 h in warmer digestions, while intact TnT disappearance was greater as both time and digestion temperature increased. Meat aging and µ-calpain activity are influenced by both temperature and pH, but more research is necessary to fully realize their relationships.

Differences in phosphorylation of phosphoglucomutase 1 in beef steaks from the longissimus dorsi with high or low star probe values.

The objective of this study was to use proteomics to identify alterations of proteins that are related to tenderness. The longissimus dorsi (LD) were removed from ten beef carcasses at 24 h postmortem, and the two with the highest (HSP; average kg of force=6.57) and lowest star probe values (LSP; average kg of force=3.75) at 14 days postmortem were identified. Two-dimensional PAGE was used to compare the sarcoplasmic fraction of the LD from HSP and LSP steaks. A series of spots identified as phosphoglucomutase 1 (PGM1) were identified. Only the most alkaline isoform was identified as being unphosphorylated. The least phosphorylated isoform (isoform 5) had a greater density of the total protein (P<0.05) and phosphorylated protein (P<0.05) in the samples from HSP steaks compared to the samples from LSP steaks. This study illustrates the importance of identifying posttranslational modifications of proteins in the search for biomarkers.

Relationship between gilt behavior and meat quality using principal component analysis.

Pig on-farm behavior has important repercussions on pig welfare and performance, but generally its relationship with meat quality is not well understood. We used principal component analysis to determine the relationship between meat quality traits, feeding patterns, scale activity, and number of conflict-avoidance interactions. The first principal component indicated that gilts with greater daily feed intake stayed longer in the feeder and their meat had increased intramuscular fat (IMF), was lighter in color, and, in the second principal component, had better juiciness, tenderness, chewiness, and flavor. Meat from gilts with lower scale activity scores appeared to have more IMF but greater drip losses (DL). The third principal component suggested that dominant gilts could gain priority access to the feeder, eating more and growing fatter. In conclusion, except for the slight associations with IMF and DL, gilt scale activity and conflict-avoidance behaviors were not good indicators of final meat quality attributes.