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.

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.

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.

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.

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.

Evidence of decreased muscle protein turnover in gilts selected for low residual feed intake.

The objective of this study was to evaluate the contribution of muscle protein turnover (synthesis and degradation) to the biological basis for genetic differences in finisher pigs selected for residual feed intake (RFI). Residual feed intake is defined as the difference between expected feed intake (based on the achieved rate of BW gain and backfat depth of individual pigs) and the observed feed intake of the individual pig. We hypothesized that protein turnover would be reduced in pigs selected for low RFI. Twelve gilts from a line selected for 7 generations for low RFI and 12 from a contemporary line selected for 2 generations for high RFI were paired by age and BW and fed a standard corn-soybean diet for 6 wk. Pigs were euthanized, muscle and liver samples were collected, and insulin signaling, protein synthesis, and protein degradation proteins were analyzed for expression and activities. Muscle from low RFI pigs tended to have less µ- and m-calpain activities (P = 0.10 and 0.09, respectively) and had significantly greater calpastatin activity and a decreased µ-calpain:calpastatin activity ratio (P < 0.05). Muscle from low RFI pigs had less 20S proteasome activity compared with their high RFI counterparts (P < 0.05). No differences in insulin signaling intermediates and translation initiation signaling proteins [mammalian target of rapamycin (mTOR) pathway] were observed (P > 0.05). Postmortem proteolysis was determined in the LM from the eighth generation of the low RFI pigs versus their high RFI counterparts (n = 9 per line). Autolysis of µ-calpain was decreased in the low RFI pigs and less troponin-T degradation product was observed at 3 d postmortem (P < 0.05), indicating slowed postmortem proteolysis during aging in the low RFI pigs. These data provide significant evidence that less protein degradation occurs in pigs selected for reduced RFI, and this may account for a significant portion of the increased efficiency observed in these animals.

Effect of low voltage electrical stimulation on protein and quality changes in bovine muscles during postmortem aging.

This experiment was conducted to determine the influence of low voltage electrical stimulation (ES) on the tenderness development of beef round muscles. Eight steers were slaughtered, and ES applied to one side of each carcass within 90 min of exsanguination. Steaks from M. longissimus dorsi, semimembranosus, adductor, and gracilis were vacuum packaged and aged at 4 °C for 9 d. Star probe, sensory evaluation, Western blot assays of troponin-T and µ-calpain autolysis and 2D-DIGE were conducted. ES resulted in accelerated (P<0.05) pH decline of the longissimus in the first 24h postmortem. ES did not influence (P>0.05) proteolysis and tenderness, but did alter the predominance of metabolic proteins in the soluble fraction of muscle. Aging for 9 d improved tenderness (P<0.05). The data confirmed that low voltage ES at 90 min of exsanguination had no effect on proteolysis and tenderness development in the longissimus dorsi, semimembranosus, adductor or gracilis in beef.

Divergent genetic selection for residual feed intake impacts mitochondria reactive oxygen species production in pigs.

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.

Profile of biochemical traits influencing tenderness of muscles from the beef round.

The objective of this study was to define the biochemical differences that govern tenderness and palatability of economically important muscles from the beef round using cuts with known tenderness differences. At 24h postmortem, the longissimus dorsi (LD), gracillus (GR), adductor (AD), semimembranosus (SM), sartorius (SAR), vastus lateralis (VL), and vastus intermedius (VI) muscles were removed from ten market weight beef cattle. Sensory and biochemical characteristics were determined in each cut and compared with the LD. The GR, SAR and VI had sensory traits similar to the LD while the SM, AD and VL differed. The GR, SAR, AD, and SM all had multiple biochemical characteristics similar to the LD, while the VI and AD had numerous biochemical differences. While no one biochemical characteristic can be used to predict tenderness across all muscles, analysis of the biochemical characteristics revealed that in most beef round cuts postmortem proteolysis provided a good indication of the tenderization occurring during aging.

Myosin light chain 1 release from myofibrillar fraction during postmortem aging is a potential indicator of proteolysis and tenderness of beef.

The objective of this study was to identify proteins in bovine longissimus dorsi muscle that are related to tenderness. Two dimensional difference in gel electrophoresis (2D-DIGE) was used to compare the sarcoplasmic fractions from steaks that differed in star probe values at 14 days postmortem. The intensity of myosin light chain 1 (MLC1) was greater in the sarcoplasmic fraction prepared from steaks that had lower star probe values. It was hypothesized that µ-calpain catalyzes the release MLC1 into the sarcoplasmic fraction. Myofibrils from beef longissimus dorsi were purified and incubated with µ-calpain and the appropriate buffer controls. µ-Calpain was added at 1.23 µg (0.0875 U) of pure µ-calpain/mg myofibrillar protein. Incubations of one and 120 min had a greater abundance of MLC1 in the supernatants than the control incubations. As a consequence of µ-calpain proteolysis, MLC1 is rapidly released from the myofibril and is a potential indicator of proteolysis and improvement in beef tenderness.

Effects of selection for decreased residual feed intake on composition and quality of fresh pork.

The objectives of this study were to determine the extent to which selection for decreased residual feed intake (RFI) affects pork composition and quality. Pigs from the fifth generation of selection for decreased RFI (select) and a randomly selected line (control) were utilized. Two experiments were conducted. In Exp. 1, barrows (22.6 ± 3.9 kg) from select and control lines were paired based on age and BW. The test was conducted in 8 replicates of pairs for the test period of 6 wk. Calpastatin activity and myosin isoforms profile were determined on samples from the LM. Control barrows were heavier (59.1 vs. 55.0 kg; P < 0.01) at the end of the test period. Calpastatin activity was greater (P < 0.01) in LM of select barrows than control barrows. In Exp. 2, composition and quality of gilts (114 kg) from control and select lines were determined. The model included fixed effects of line, slaughter date, melanocortin-4 receptor (MC4R) genotype, barn group, line × slaughter date, genotype × line interactions, a covariate of off-test BW, and sire, pen, and litter fitted as random effects. The select line (n = 80) had 0.043 kg less (P < 0.05) RFI per day than the control line (n = 89). Loin quality and composition were determined at 2 d postmortem. Desmin degradation was measured at 2 and 7 d postmortem. Purge, cook loss, sensory traits, and star probe texture were measured at 7 to 10 d postmortem on cooked chops. Residual correlations between RFI and composition and quality traits were calculated. Compared with the control line, carcasses from the select line tended to have less (P = 0.09) backfat, greater (P < 0.05) loin depth, and greater (P < 0.05) fat free lean. Loin chops from the select line had less (P < 0.01) intramuscular lipid content than loin chops from control line. Significant residual correlations between RFI and both tenderness (r = 0.24, P < 0.01) and star probe (r = -0.26, P < 0.01) were identified. Selection for decreased RFI has the potential to improve carcass composition with few effects on pH and water-holding capacity. However, decreased RFI could negatively affect tenderness and texture because of decreased lipid content and decreased postmortem protein degradation.

Identification of genetic markers associated with residual feed intake and meat quality traits in the pig.

Residual feed intake (RFI) has become increasingly important and is being considered as a more reasonable approach to evaluate feed efficiency in livestock. However, the cost and technical difficulties in measuring this trait restrict the extensive adoption of RFI selection, and this makes marker assisted selection (MAS) a feasible tool. In addition, the effects on meat quality caused by low RFI selection have yet to be clarified. In this study, 11 SNPs from eight candidate genes were evaluated in a Yorkshire pig experimental population (n=169) consisting of a low RFI selection line and a randomly selected control line. Associations of these SNPs with RFI, growth rate, carcass composition, and meat quality measures including water holding capacity, pH at 2d postmortem, meat color and sensory traits were analyzed. The SNPs FTO p.Ala198Ala and TCF7L2 c.646+514A>G showed significant (P<0.05) and suggestively significant (P<0.1) associations with RFI, respectively. The MC4R SNP p.Asp298Asn was associated with backfat but it was not with ADG and meat quality attributes. Both SNPs within HNF1A were associated with intramuscular lipid content and sensory juiciness. The SNPs ACC1 c(*)384C>T and TCF7L2 c.646+514A>G were significantly (P<0.05) associated with ADG. The SNPs CTSZ p.Arg64Lys and TCF7L2 c.646+514A>G were associated with both visual scoring of meat color and the objective L-value measure of meat color. This study has identified potential genetic markers suitable for MAS in improving RFI, ADG, and meat color traits, but these associations need to be validated in other larger populations.