Intramuscular connective tissue (IMCT) collagen is an important factor in meat quality. This study analyzed the characteristics of type I and III collagen in the IMCT of the semitendinosus (SD) and longissimus dorsi (LD) of Wuzhumuqin sheep at different growth stages (6, 9, 12, and 18 months). Utilizing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR), collagen types I and III were successfully isolated and shown to contain an intact triple helix structure. Immunofluorescence revealed that these collagens were located in the endomysium and perimysium. Collagen-related genes were significantly expressed in sheep aged 9 and 12 months. The amino acid content increased with age in type I collagen whereas it decreased in type III collagen. Furthermore, type III collagen contained more hydroxyproline (Hyd) than type I collagen. Differential scanning calorimetry (DSC) revealed that the thermal stability of collagen increased with age, accompanied by a decrease in solubility. Semitendinosus muscle had more collagen cross-linkages than LD muscle due to the high pyridinoline (Pyr) content in the endomysium. Finally, a correlation analysis highlighted the multiple correlations between characteristics in different types of collagen during sheep growth. In summary, the collagen characteristics in the IMCT of sheep were impacted by collagen type, muscle type, and age. Furthermore, the various correlations between these characteristics may play an important role in the development of IMCT.

Adipose tissue is a crucial economically significant trait that significantly influences the meat quality and growth performance of domestic animals. To reveal the changes in adipose tissue metabolism during the growth of naturally grazing sheep, we evaluated the thickness, adipocyte morphology, fatty acid profile, and metabolite profile of subcutaneous adipose tissue (SAT) from naturally grazing Sunit sheep at 6, 18, and 30 months of age (referred to as Mth-6, Mth-18, and Mth-30, respectively). The fat thickness and adipocyte number were significantly increased with the growth of the sheep (p < 0.05), and the increase of which from Mth-18 to Mth-30 was less than that from Mth-6 to Mth-18. Additionally, the alpha-linolenic acid metabolism was enhanced and fatty acid (FA) elongation increased with growth. The metabolomic analysis revealed 76 differentially expressed metabolites (DEMs) in the SAT in different growth stages. Interestingly, we observed elongation of FAs in lipids correlated with sheep growth. Furthermore, the expression of acylcarnitines was downregulated, and fatty acid amides, aspartic acid, acetic acid and phosphocholine were upregulated in Mth-18 and Mth-30 compared to Mth-6. Altogether, the study found that the difference in SAT in Mth-6 was great compared to Mth-18 and Mth-30. An increase in fat deposition via adipocyte proliferation with the growth of the sheep in naturally grazing. The DEMs of acylcarnitines, fatty acid amides, aspartic acid, acetic acid, and phosphocholine emerged as potential key regulators of adipose tissue metabolism. These findings illustrate the variation in and metabolic mechanism of sheep adipose tissue development under natural grazing, thus providing valuable insights into improving the edible quality of sheep meat and developing the mutton sheep industry.

This study elucidated the regulatory mechanisms of age-related meat flavor precursors in naturally grazed Sunit sheep of different ages (6, 18, and 30 months) by analyzing their metabolite and mRNA profiles. The longissimus dorsi muscle was sampled from each group and subjected to metabolomics and transcriptomics analyses. A total of 395 differential metabolites (DMs) and 1482 differentially expressed genes (DEGs) were detected across the age groups. As the age increased, the expression levels of GOT1 and GLUL increased, activating arginine biosynthesis and alanine, aspartate, and glutamate metabolism pathways, which promoted the accumulation of umami compounds (L-glutamate and L-glutamine). Meanwhile, the expression level of LPIN1 increased with age, promoting glycerophospholipid metabolism and contributing to the development of lipid-related aroma. FADS1 and FADS2 expressed the highest levels at age Mth_18. This pattern influenced the unsaturated fatty acid biosynthesis pathway and consequently had a regulatory effect on the DHA levels. An amino acid metabolic regulatory network that involved arginine biosynthesis, alanine, aspartate and glutamate metabolisms, and arginine and proline metabolisms was established. This study provided insights into the variations in meat flavor precursors among sheep of different ages and elucidated the underlying regulatory mechanisms.

Horse bone is rich in collagen, with a composition similar to that of human collagen. Collagen peptides supply nutrients needed for human growth that act as antioxidants, lower blood pressure. This study explored the extraction of collagen and the preparation of collagen short peptides from Mongolian horse bones. Bones were collected from horses of varying ages, and the collagen content along with calcium salt distribution were observed through staining and imaging analyses. Next, the bones were processed into a powder and then subjected to ultra-high-pressure processing for degreasing. The degreasing conditions were optimised by single-factor and orthogonal tests. Following this, collagen was extracted using an acid-enzymatic method, and its structural characteristics and thermal stability were assessed. The collagen short peptides were extracted from the collagen samples, and the effects of the enzymatic hydrolysis time, temperature, pH, and enzyme amount on the extraction rate were evaluated. Finally, the resulting collagen peptides were analysed for antioxidant activity. In summary, this experiment optimised the extraction conditions for horse bone collagen, demonstrating that the ultra-high-pressure method minimally affects collagen structure, and the extraction rate was high. Hence our method has significant development potential.

The color of carcass fat is an important factor in meat quality. To investigate the characteristics and changes in lipid metabolism of SAT in Mongolian cattle at 34 M of age compared with the control group, we evaluated the color, relative expression of genes associated with browning, and profiles of lipid metabolites by using qPCR and non-targeted lipidomics techniques. Overall, the yellowness value and relative expression of mitochondrial biogenesis–specific markers, thermogenic, UCP2, and beige adipocyte marker genes in the SAT of 34 M cattle were higher than those control (p < 0.05). Using multivariate analysis, 172 significantly different lipids (SDLs) were identified. Triacylglycerols (TGs) and phosphatidylcholines (PCs) had high relative contents with abundant unsaturated fatty acids. The upregulation of TGs observed in the SAT of 34 M cattle mainly consisted of medium- and long-chain fatty acids. Pathway analysis demonstrated that 172 SDLs were primarily involved in glycerophospholipid, glycerolipid, ether lipid, and sphingolipid metabolism. In summary, yellow fat of naturally grazed cattle was impacted by many factors such as lipid metabolism, browning genes expression and age. These findings provide new insight into the characteristics and metabolic pathways of adipose tissue in natural grazing Mongolian cattle.

Background: The longissimus dorsi muscle of the camel was chosen as the experimental material in order to investigate the impact of plasma electric field assisted freezing on the quality and freezing process of Bactrian camel meat. Methods: The effect of the auxiliary plasma electric field of different field strengths (1 kV/m, 3 kV/m and 5 kV/m) on the freezing velocity of the camel meat and the distribution of ice crystals as well as the diameter and roundness of ice crystal in the frozen meat were studied and analyzing them with the help of the thermodynamic theory. Result: The findings demonstrated that the meat samples in the auxiliary 5 kV/m plasma field environment took 60 min and 30 min, respectively, at -20°C and -35°C, to pass the maximal ice crystal production zone. The tissue sections revealed that at -20°C and -35°C assisted 5 kV/m plasma field freezing, the smallest ice crystal area and grain size were formed, the roundness of the ice crystals was highest. Using Boltzmann’s entropic equation to calculate the system’s entropy, the results revealed that the meat samples frozen by the aided 5 kV/m plasma electric field had the lowest entropy at -20°C and -35°C. The electric field assisted freezing requires less energy to improve the subcooling degree and accelerate the freezing rate of meat samples, proving that the auxiliary 5 kV/m plasma electric field can significantly improve the system frozen meat moisture vitrification degree and can make the crystallization process more controllable.