To investigate the effect of dietary sodium propionate (SP) on muscle metabolism and meat quality in lambs, 12 three-month-old Dorper (ewe) × Suffolk (ram) crossbred lambs with good body condition and a body mass of (22.70 ± 1.91) kg were selected and randomly divided into a control group (fed a basal diet) and an SP group (fed 20 g of SP per animal per day + a basal diet) for a 90-day feeding trial. After slaughter, the longissimus dorsi muscle was collected for the determination of fatty acid composition and muscle metabolic profiles using widely targeted metabolomics based on gas chromatography-mass spectrometry (GC-MS) and ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that dietary SP significantly increased the protein content in the longissimus dorsi muscle (P < 0.05), and decreased the redness, yellowness, pH_{45 min} and pH_{24 h} values (P < 0.05). Meanwhile, dietary SP significantly increased the contents of nonadecanoic acid, arachidic acid, heneicosanoic acid, cis-11-eicosenoic acid, cis-13,16-docosadienoic acid, cis-8,11,14-eicosatrienoic acid, and α-linolenic acid in the muscle (P < 0.05), and decreased the content of cis-10-pentadecenoic acid (P < 0.05). Widely targeted metabolomics analysis identified 1032 metabolites in the longissimus dorsi muscles of the two groups, among which 152 substances were significantly differential metabolites (SDMs). In the SP group, 3-iodo-L-tyrosine, (R)-2-hydroxy-3-phenylpropionic acid, lysophosphatidylserine (18:0), 5’-adenylyl sulfate, and DL-glyceraldehyde-3-phosphate were significantly upregulated. However, carnitine C_9:1, carnitine C_18:1, carnitine C_13:0, and carnitine C_9:0 were significantly downregulated. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that these SDMs were significantly enriched in metabolic pathways such as protein digestion and absorption, fatty acid elongation, amino acid biosynthesis, and unsaturated fatty acid biosynthesis. In conclusion, dietary SP may affect the metabolic homeostasis of lamb muscle by regulating amino acid and lipid metabolism via multiple signaling pathways and targets, thereby increasing muscle protein content, optimizing muscle fatty acid composition, and ultimately improving the eating quality and nutritional value of lamb meat.

The Longissimus dorsi muscle of Sunit sheep was selected to analyse changes in the content and activity of adenosine monophosphate-activated protein kinase (AMPK), glycolysis indicators and meat quality indicators during postmortem aging (4 ℃/0, 24, 48, 72 and 96 h), in order to explore the influence of AMPK content and activity on the glycolysis and the aging process after slaughter and determine the best aging time. The results showed that the content and activity of phosphorylated AMPK (p-AMPK) increased firstly and then decreased, reaching the highest value at 24 h. In regard to glycolysis indicators, the pH decreased significantly within 24 h after slaughter; the contents of muscle glycogen and glucose gradually decreased with increasing aging time; the lactic acid content reached its maximum value at 24 h after slaughter. As for meat quality indicators, the shear force reached its maximum value at 24 h, then decreased, and tended to level off after 48 h; the color parameters a* and b* first increased and leveled off after slaughter, while L* value reached its peak at 96 h after slaughter. The number of volatile flavor compounds identified at 0, 24, 48, 72 and 96 h was 29, 30, 41, 40 and 46, respectively. The largest number of aldehydes was found at 48 h, and the aldehydes contributed to improve the overall flavor of sheep meat. In summary, changes in AMPK content and activity at different time points after slaughter will cause changes in glycolysis indicators and consequently affect changes in meat quality indicators. At 48 h after slaughter, mutton has better quality and flavor, and is suitable for processing and eating.

Five-month-old captive Hulunbuir sheep (Baerhu and short-fat-tailed, n =10 for each) were selected to study the effect of important gene networks related to fat metabolism on fat distribution and fatty acid profile. The results showed that the relative mRNA expression of the fat mass and obesity associated (FTO) and methyltransferase 3 (METTL3) genes in longissimus dorsi and triceps brachii, the relative mRNA expression of the AMP-activated proteinkinase (AMPK) gene in triceps brachii, biceps femoris and subcutaneous fat, and the relative mRNA expression of the carnitine palmitate transferase (CPT1) gene in longissimus dorsi, subcutaneous fat and tail fat were significantly higher in Baerhu sheep than in short-fat-tailed sheep (P < 0.05), and the proportion of saturated fatty acids in longissimus dorsi and biceps femoris, the proportion of polyunsaturated fatty acids in subcutaneous and tail fat, and the proportion of monounsaturated fatty acids in tail fat of Baerhu sheep were significantly higher than those in short-fat-tailed sheep (P < 0.05). The relative mRNA expression of the acetyl-CoA carboxylase (ACC) gene in muscle, and FTO, METTL3, PPARγ (peroxisome proliferators-activated receptor γ) and ACC in subcutaneous fat, the content and mass of intramuscular fat, total carcass fat mass, carcass fat percentage, the proportion of polyunsaturated fatty acids in longissimus dorsi and the proportion of saturated fatty acids in tail fat were significantly lower in Baerhu sheep than in short-fat-tailed sheep (P < 0.05). In conclusion, the differential expression of this gene network can affect fat metabolism and energy metabolism of different strains of Hulunbuir sheep to a certain extent and consequently fat distribution and fatty acid profile.

In order to explore the effect of dietary supplementation of Clostridium butyricum on the volatile flavor substances in the meat of small-tailed Han sheep during postmortem aging and its possible mechanism, the Longissimus dorsi muscle of small-tailed Han sheep slaughtered at the age of six months was taken for postmortem maturation at 4 ℃, and then the volatile flavor substances, the contents of lipid metabolism-related enzymes including adenosine monophosphate activated protein kinase (AMPK), acetyl CoA carboxylase (ACC) and carnitine lipoyltransferase 1 (CPT1) were measured on days 0, 1, 2, 3, 4 and 5. The results of electronic nose test showed that the contents of alkanes, hydroperoxide and nitrogen oxides in the C. butyricum supplementation group were higher than in the control group without C. butyricum supplementation. According to the results of gas chromatography-mass spectrometry (GC-MS), the types of aldehydes, alcohols and ketones in the C. butyricum group were more than in the control group, while the contents of fatty oxidation products such as octanal, nonanal, decanal and heptaldehyde were obviously reduced. The key flavor substances common to both groups, as determined by relative odor activity value (ROAV), included octanal, nonanal, trans-2-decenal and 1-octen-3-ol, nonanal being the greatest contributor to the flavor of lamb meat. Compared with the control group, the contents of AMPK and CPT1 in the C. butyricum group decreased significantly during postmortem aging (P < 0.05), while the contents of ACC in the C. butyricum group were significantly higher than those in the control group at 0, 1, 3 and 5 days postmortem (P < 0.05). The correlation analysis showed that AMPK and CPT1 were significantly positively correlated with nonanal (P < 0.001), while ACC was significantly negatively correlated with nonanal and decanal (P < 0.001). In conclusion, the addition of C. butyricum to the diet can affect the volatile flavor substances in the meat of small-tailed Han sheep during postmortem aging by regulating the AMPK-ACC-CPT1 signaling pathway.

The objective of this study was to investigate the effect of dietary supplementation with Clostridium butyricum on the fatty acid metabolism and meat quality of small-tailed Han sheep. A total of 24 three-month-old small-tailed Han sheep in good body condition and with body mass of (28.85 ± 2.01) kg were selected and randomly divided into two groups: the control group was fed a basal diet (a typical corn-soybean diet), and the Clostridium butyricum group was fed the basal diet supplemented with Clostridium butyricum with a viable count of 5 × 10⁸ CFU/g at a dose of 5 g/d. The feeding period lasted for 90 days. After slaughter, rumen fluid was collected for metagenomic analysis, and Longissimus dorsi muscle was harvested to determine its eating quality, fatty acid composition, and gene expression associated with fatty acid metabolism by gas chromatography (GC) and real-time fluorescent quantitative polymerase chain reaction (qPCR). The results showed that feeding Clostridium butyricum significantly improved the brightness value (L^*), redness value (a^*), pH_{24 h}, and intramuscular fat content (P < 0.05), and reduced the shear force of lamb meat (P < 0.05). In addition, the relative contents of palmitic acid and stearic acid were significantly lower (P < 0.05) and the relative contents of oleic acid, α-linolenic acid, eicosapentaenoic acid were significantly higher in Longissimus dorsi from the Clostridium butyricum group than the control group (P < 0.05). qPCR results showed that dietary supplementation with Clostridium butyricum significantly increased the gene expression of sterol regulatory element binding protein 1C (SREBP-1C), stearoyl-CoA desaturase (SCD), peroxisome proliferator-activated receptor gamma (PPARγ), and acetyl-CoA carboxylase (ACC) (P < 0.05). Metagenomic analysis showed that dietary supplementation with Clostridium butyricum increased the abundance of Firmicutes, Clostridium, and Fibrobacters (P < 0.05), and significantly decreased the abundance of Proteobacteria, Butyrivibrio, and Parabacteroides in rumen fluid (P < 0.05). Correlation analysis showed that the relative abundance of Ruminobacter, Prevotella, and Lactobacillus were significantly positively correlated with unsaturated fatty acids relative contents (P < 0.05). In conclusion, the addition of Clostridium butyricum to the diet can change the microbial composition of the rumen, leading to an increase in the gene expression of SREBP-1C, SCD, PPARγ, and ACC to promote fatty acid deposition, and finally improving the eating quality and nutritional value of small-tailed Han sheep meat.

In this study, we aimed to the effect of dietary selenium supplementation on the antioxidant capacity and quality of mutton during postmortem aging. Forty 18-month-old Erlangshan white cashmere goats in good condition with an average body mass of (41.20 ± 3.34) kg were randomly divided into a control group (fed a basal diet) and a selenium-rich yeast group (fed a basal diet + selenium-rich yeast (0.5 mg/kg)). The feeding experiment lasted for 90 days conducted and the longissimus dorsi muscle was taken after slaughter for the determination of selenium content. Meat quality and antioxidant properties were determined at 0, 24, 48, 72 and 96 h postmortem. The results showed that dietary addition of selenium-rich yeast effectively enriched selenium in goat meat, and significantly reduced the shear force of goat meat during postmortem aging. Feeding selenium-rich yeast had no significant effect on the richness of volatile flavor substances in goat meat during postmortem aging, but it decreased the production rate of various flavor substance, resulting in a significant increase in the contents of 1-octen-3-ol at 96 h and a significant decrease in the contents of 1-heptanol from 0 to 96 h and 1-heptanol and 2-ethylhexanol, nonanal and octanal at 96 h compared with the control group (P < 0.05). Antioxidant enzyme activities were significantly higher in the selenium-rich yeast group than in the control group (P < 0.05); the carbonyl content was significantly lower than that of the control group at 48-96 h (P < 0.05), and the sulfhydryl content was significantly higher than that of the control group (P < 0.05). Additionally, it was shown that the malondialdehyde (MDA) content, an indicator of the degree of fat oxidation, was significantly lower than that of the control group (P < 0.05).