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The objective of this study was to investigate the differences in the muscle proteome of grass-fed and grain-fed cattle. Eight Japanese Black Cattle 10 mo of age were separated randomly into 2 groups: 1) grazing (grass-fed) and 2) concentrate (grain-fed) groups. All cattle were first housed individually in a stall barn and fed a combination of concentrate ad libitum and Italian ryegrass hay until 21 mo of age. After this control period, the 4 grass-fed cattle were placed on outdoor pasture, whereas the other 4 grain-fed cattle continued on the concentrate diet. The cattle were slaughtered at 27 mo of age, and tissues from the semi-tendinosus muscle were obtained for use in proteome analysis. Differential expression of muscle proteins in the 2 groups was carried out using 2-dimensional gel electrophoresis (2DE) and Western blot analyses, with subsequent mass spectrometry. Approximately 200 individual protein spots were detected and compared in each group using 2DE, of which 20 and 9 spots, respectively, showed differences in the spot intensity fox' the sarcoplasmic fraction and myofibrillar fraction. In the grazing group, the relative intensity of spots was significantly greater for adenylate kinase 1 and myoglobin in the sarcoplasmic fraction, and for slow-twitch myosin light chain 2 in the myofibrillar fraction (P < 0.05), than the concentrate group. The relative spot intensity of several glycolytic enzymes was significantly greater in the grazing group, such as [beta]-enolase 3, fructose-1,6-bis-phosphate aldolase A, triosephosphate isomerase, and heat shock 27 kDa protein (P < 0.05). Moreover, significantly greater slow twitch of troponin T, troponin I, and myosin heavy chain of semitendinosus muscle was detected in the grazing group than in the concentrate group using Western blot analysis (P < 0.05). Several previous reports have described that the slow-twitch muscle contents affect elements of nutrition, flavor, and food texture of meat. This study revealed muscle fiber type conversion to slow-twitch tissues from fast-twitch tissues occurring with change in the energy metabolic enzyme when cattle were grazed in the latter fattening period. Although analyses of the influence on elements of nutrition, flavor, and food texture were not done for this study, these results show that slow-twitch converted muscle resulting from the grazing of cattle might modify several meat characteristics. Key words: beef cattle, grazing, muscle, myofibrillar protein, proteome analysis, sarcoplasmic protein

Multiple nucleotide sequences of complementary DNA (cDNA) of bovine troponin T (TNT) isoforms expressed in the adult skeletal muscles were determined to facilitate the elucidation of the TnT degradation progress during postmortem aging of muscles. Fresh muscle samples were excised from the lingual, masseter, pectoralis, diaphragm, psoas major, longissimus thoracis, spinnalis, semitendinosus, semimembranosus, and biceps femoris muscles of three Holstein cows within 1 h of slaughter. Complementary DNA fragments of fast and slow TnT isoforms expressed in each muscle were amplified by reverse-transcribed PCR. Consequently, four major fragments of fast TnT and two fragments of slow TnT, all of which contained the complete coding region, were obtained. The sequence determination of these fragments revealed that at least eight and two isoforms were generated by the alternative splicing from bovine fast and slow TnT messenger RNA, respectively. In the fast TnT isoforms, five small variable exons were observed; three of these five exons were in the amino (N)-terminal region. The calculated molecular weight of fast and slow TnT isoforms ranged from 29,816 to 32,125 and from 30,166 to 31,284, respectively. The deduced amino acid sequences revealed that the N-terminal region of all the TnT isoforms was extremely glutamic acid-rich. Reverse-transcribed PCR analysis revealed that expression of each of these isoforms was distributed in a fast or slow muscle-specific manner. Given that TnT degradation has been reported to accompany a decrease in glutamic acid content in the conventional 30-kDa degradation product, the sequence data suggested that the 30-kDa fragment seem to be generated by the proteolytic removal of the glutamic acid-rich N-terminal ends. The multiplicity of TnT isoforms may result in a complicated pattern of TnT degradation on SDS-PAGE gel during beef aging. Key Words: Aging, Amino Acid Sequence, Cattle, Degradation, Troponins

Lactoperoxidase (LPO)-treated yogurt has low hardness and soft, smooth texture, according to research comparing rheological properties of LPO-treated yogurt with those of controls. This research used empirical physical evaluations and dynamic oscillatory testing. Other possible causes of rheological changes would be the impact of radicals on rheological properties. It is possible that oxygen radicals damage and degrade protein. Further research is required to establish the impact of hypothiocyanite ion produced by LPO-catalyzed oxidation on modification or denaturation of milk proteins, producing changes in rheological properties of yogurt.

During meat processing, the splitting of the connectin molecule in striated muscle is important for meat texture because it reduces the meat's elasticity. A new study analyses the differences in molecular weights and partial amino acid sequences of connectin for cattle, chicken and pig skeletal muscles. It is shown that peptide mapping analysis differs according to animal type and amino acid sequences also differ at fibronectin type 3 and immunoglobulin-like domains. It is suggested that different meat textures may be related to connectin breakdown.