No abstract

No abstract

Postmortem (PM) and mu-calpain-induced degradation of specific skeletal muscle proteins was monitored by SDS-PAGE and Western blotting. Samples were removed from bovine longissimus thoracis (LT) at approximately 45 min PM for the preparation of at-death (0-d) myofibrils (MF). The LT was excised at 1 d PM, vacuum-packaged, and stored at 2 degrees C. Samples were removed for Warner-Bratzler shear force analysis and biochemical analysis at 1, 3, 7, 14, 28, and 56 d PM. The protease mu-calpain was purified from bovine skeletal muscle and used to digest at-death MF at pH 5.6, 4 degrees C, 100 microM CaCl2. Degradation of the proteins titin, nebulin, filamin, desmin, and troponin-T was monitored in the PM and mucalpain-digested samples by using SDS-PAGE and Western blotting. The PM samples that had significantly lower shear force (LSF) values (P < .05) at 1 d PM exhibited faster degradation of these five proteins than the higher shear force (HSF) samples. In LSF samples, the intact titin band (T1) was absent by 7 d PM and nebulin was absent by 3 d PM. In LSF samples, some filamin was degraded by 3 d PM, but in HSF samples degradation was not apparent until 14 d PM. In LSF samples, desmin was degraded more rapidly PM than in HSF samples. Troponin-T was broken down PM to yield two major polypeptides of approximately 28 and 30 kDa; these polypeptides appeared earlier PM in LSF samples. Degradation products, similar to those observed PM, for all five proteins also were detected in Western blots of mu-calpain-digested MF, suggesting the calpain system plays a key role in PM protein degradation. ABSTRACT:Postmortem (PM) and m-calpaininduced degradation of specific skeletal muscle proteins was monitored by SDS-PAGE and Western blotting. Samples were removed from bovine longissimus thoracis ( L T ) at approximately 45 min PM for the preparation of at-death (0-d) myofibrils (MF). The LT was excised at 1 d PM, vacuum-packaged, and stored at 2°C. Samples were removed for WarnerBratzler shear force analysis and biochemical analysis at 1, 3, 7, 14, 28, and 56 d PM. The protease m-calpain was purified from bovine skeletal muscle and used to digest at-death MF at pH 5.6, 4°C, 100 mM CaCl 2 . Degradation of the proteins titin, nebulin, filamin, desmin, and troponin-T was monitored in the PM and m-calpain-digested samples by using SDS-PAGE and Western blotting. The PM samples that had significantly lower shear force (LSF) values ( P < .05) at 1 d PM exhibited faster degradation of these five proteins than the higher shear force (HSF) samples. In LSF samples, the intact titin band ( T 1 ) was absent by 7 d PM and nebulin was absent by 3 d PM. In LSF samples, some filamin was degraded by 3 d PM, but in HSF samples degradation was not apparent until 14 d PM. In LSF samples, desmin was degraded more rapidly PM than in HSF samples. Troponin-T was broken down PM to yield two major polypeptides of approximately 28 and 30 kDa; these polypeptides appeared earlier PM in LSF samples. Degradation products, similar to those observed PM, ...

Establishing relationships among specific quality traits is important if significant progress toward developing improved pork quality is to be realized. As part of a study to examine the individual effects of genes on meat quality traits in pigs, a three-generation resource family was developed. Two Berkshire sires and nine Yorkshire dams were used to produce nine F1 litters. Sixty-five matings were made from the F1 litters to produce four sets of F2 offspring, for a total of 525 F2 animals used in the study. These F2 animals were slaughtered at a commercial facility upon reaching approximately 110 kg. Carcass composition traits, pH measurements, and subjective quality scores were made at 24 h postmortem. Loin samples (n = 525) were collected at 48 h postmortem, and meat quality traits were evaluated. These traits included pH (48 h), Hunter L-values, drip loss, glycolytic potential, ratio of type IIa/IIb myosin heavy chains (IIa/IIb), total lipid, instrumental measures of tenderness using the Star Probe attachment of the Instron, cook loss measurements, and sensory evaluations. Significant phenotypic correlations were found between many carcass, instrumental, and biochemical measurements, and sensory quality traits. Star Probe measurements were significantly correlated with drip loss (0.29), glycolytic potential (0.30), pH (-0.29), total lipid (-0.14), and Hunter Lvalues (0.28). Drip loss was significantly correlated with glycolytic potential (0.36), pH (-0.28), IIa/IIb (-0.10), and Hunter L-values (0.33). Hunter L-values were also significantly correlated with total lipid (0.33) and IIa/ IIb (-0.11). Sensory tenderness, flavor, and off-flavor scores were significantly correlated with drip loss, pH, and glycolytic potential measurements. Marbling score, total lipid, and drip loss were not significantly correlated with sensory juiciness scores, but cooking loss was. Marbling and total lipid were significantly correlated with firmness scores (0.37 and 0.31, respectively). Taken together, the data in this study suggest that changes in some meat quality traits can affect many other meat quality attributes. The correlations yield information that could aid in directing future studies aimed at understanding the underlying biological mechanisms behind the development of many quality traits. ABSTRACT: Establishing relationships among specific quality traits is important if significant progress toward developing improved pork quality is to be realized. As part of a study to examine the individual effects of genes on meat quality traits in pigs, a three-generation resource family was developed. Two Berkshire sires and nine Yorkshire dams were used to produce nine F1 litters. Sixty-five matings were made from the F1 litters to produce four sets of F2 offspring, for a total of 525 F2 animals used in the study. These F2 animals were slaughtered at a commercial facility upon reaching approximately 110 kg. Carcass composition traits, pH measurements, and subjective quality scores were made at 24 h postmortem. Loin samp...

Molecular genetic markers can be used to identify chromosomal regions that contain quantitative trait loci (QTL) that control meat quality and muscle composition traits in farm animals. To study this in pigs, a resource family was generated from a cross between two Berkshire grand sires and nine Yorkshire grand dams. A total of 525 F2 progeny from 65 matings of F1 parents were produced. Phenotypic data on 28 meat quality traits (drip loss, water holding capacity, firmness, color, marbling, percentage cholesterol, ultimate pH, fiber type, and several sensory panel and cooking traits) were collected on the F2 animals. Animals were genotyped for 125 microsatellite markers covering the entire genome. Least squares regression interval mapping was used for QTL detection. Significance thresholds were determined by permutation tests. A total of 60 QTL were detected at the 5% chromosome level for meat quality traits, on Chrs 1, 2, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, 18, and X, of which 9 and 1 QTL were significant at the 5% and 1% genome-wise levels (on Chrs 1, 5, 12, 15, and 17), respectively.