Walnut green husks (WGHs), by-products of walnut production, are believed to possess antimicrobial properties, making them a potential alternative to antibiotics. In this study, the antibacterial activities of three extracts, derived from WGH, against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli were investigated, and the antibacterial mechanisms of an anhydrous ethanol extract of WGH (WGHa) were examined. The results showed that WGHa exhibited inhibitory effects on all tested bacteria. The ultrahigh-performance liquid chromatography–tandem mass spectrometry analysis revealed that the major active compounds present in WGHa were terpenoids, phenols, and flavonoids. Treatment with WGHa resulted in the leakage of intracellular ions and alkaline phosphatase; a reduction in intracellular ATP content, ATPase activity, and nucleic acid content; as well as cellular metabolic viability. The transmission electron microscopy images showed varying degrees of cell deformation and membrane damage following WGHa treatment. The transcriptome sequencing and differentially expressed gene enrichment analyses revealed an up-regulation in pathways associated with RNA degradation, translation, protein export, and oxidative phosphorylation. Conversely, pathways involved in cell movement and localization, as well as cell wall organization and carbohydrate transport, were found to be down-regulated. These findings suggest that WGHa alters cell membrane permeability and causes damage to the cell wall. Additionally, WGHa interferes with cellular energy metabolism, compromises RNA integrity, and induces DNA replication stress, consequently inhibiting the normal growth and proliferation of bacteria. These findings unveiled the antimicrobial mechanisms of WGHa, highlighting its potential application as an antibiotic alternative.

In this study, Candida utilis, Lactobacillus plantarum, and non-starch polysaccharide enzymes (cellulase, laccase, β-glucanase, xylanase, and mannanase) were employed to examine the effects of various microorganism–enzyme combinations on the nutritional composition, fiber structure, and fermentation quality of corn stover and wheat straw. Furthermore, the synergistic effects of these treatments were assessed through the use of in vitro rumen fermentation. The results showed that the microorganism–enzyme combinations significantly increased the crude protein content (p < 0.05), while reducing the acid detergent fiber and neutral detergent fiber levels (p < 0.05) in both substrates. The fermentation broth pH decreased (p = 0.06 for corn stover; p < 0.05 for wheat straw) as a result of the treatments, with a significant increase in the lactate concentration (p < 0.05). The reducing sugar levels varied across the treatments (p < 0.05). Mycotoxin analysis revealed trace amounts of zearalenone, well below the Chinese feed hygiene standard. Scanning electron microscopy showed structural modifications, including fiber breakage and surface wrinkling, in the treated substrates. In vitro rumen fermentation demonstrated significant changes in the NH₃-N production and volatile fatty acid profiles (p < 0.05). In conclusion, the addition of different microorganism–enzyme combinations can effectively improve the nutritional composition, fiber structure, and fermentation quality of corn stover and wheat straw. Among the treatments, the T3 group (25% each of C. utilis, L. plantarum, cellulase, and laccase, with a total addition ratio of 0.3% w/w) exhibited the most pronounced improvement in nutritional value for both corn stover and wheat straw. These findings suggest that microorganism–enzyme combinations effectively enhance the nutritional and fermentative quality of agricultural residues.

This study was conducted to investigate the effects of dietary supplementation with rumen-protected arginine (RP-Arg) on growth performance, rumen fermentation parameters, microbial diversity, and blood physiological and biochemical indices in fattening Altay sheep. A total of 24 healthy, 6-month-old Altay male lambs were randomly assigned to three groups, with eight replicates per group. The control group received a basal diet, while the experimental groups were supplemented with either 0.50% or 1.00% RP-Arg on a dry matter basis, respectively. The results indicated that RP-Arg supplementation had no significant effect on feed intake, growth performance, or slaughter performance of the lambs (p > 0.05), whereas backfat thickness decreased linearly (p < 0.05). With increasing RP-Arg levels, serum low-density lipoprotein cholesterol, leptin, and catalase activity increased linearly (p < 0.05), while blood ammonia, alanine aminotransferase, and Ig M exhibited a significant quadratic increase (p < 0.05). RP-Arg supplementation led to a linear decrease in ruminal propionate and valerate concentrations (p < 0.05). Analysis of bacterial diversity revealed that the class Vampirivibrionia and the order Gastranaerophilales were biomarkers for the 0.50% RP-Arg group, while several taxa within the phyla Proteobacteria and Thermoplasmatota served as biomarkers for the 1.00% RP-Arg group. In summary, although supplementation of a forage-based diet with RP-Arg partially modified rumen microbial composition and fermentation profile, and regulated several blood biochemical parameters, it did not translate into any beneficial effects on growth performance. Larger-scale studies are therefore warranted to further elucidate the role of RP-Arg in fattening lambs.

This study investigated breed-related differences in the flavor chemistry of the longissimus thoracis muscle from Cele Black sheep (CLH), Australian White × Hu crossbred sheep (AH), and Hotan sheep (BDT). Eighteen yearling rams (six animals per group) were evaluated. Free amino acids (FAAs) were quantified by LC–MS/MS, and free fatty acids (FFAs) and volatile organic compounds (VOCs) were analyzed by GC–MS, followed by multivariate analysis, relative odor activity value (rOAV) analysis, and correlation analysis. Muscle samples from the three breeds showed comparable pH, lightness, and shear force values, whereas BDT exhibited higher redness and yellowness values. Breed-related differences were mainly observed in specific flavor-related compounds. Glutamic acid was higher in CLH (27.77 μg/g) and BDT (27.11 μg/g) than in AH (21.21 μg/g; p < 0.05). Stearic acid (C18:0) was higher in BDT (63.72 μg/g) than in CLH (41.10 μg/g) and AH (36.37 μg/g; p < 0.01). Docosatetraenoic acid (C22:4n-6) was higher in AH (9.33 μg/g) than in CLH (7.31 μg/g) and BDT (7.29 μg/g; p < 0.01). A total of 201 VOCs were annotated in raw-muscle headspace. Although overall VOC profiles were broadly similar among breeds, differences were observed in specific VOCs and annotated odor attributes, and rOAV analysis identified multiple compounds as potential aroma contributors. Correlation analysis followed by false discovery rate (FDR) correction showed that only Ile and Lys were significantly negatively correlated with o-xylene, whereas the associations of Tyr, C20:3n-6, and C22:4n-6 with VOCs were exploratory and did not remain significant. These co-variation patterns may reflect shared upstream metabolic or oxidative pathways rather than direct precursor–product conversion. These findings characterize breed-related differences in the flavor-associated chemical profiles of raw lamb muscle; however, their implications for cooked-meat aroma and perceived flavor require further validation through descriptive sensory analysis and cooked-meat VOC measurements.

This study aimed to investigate the changes in the meat quality characteristics of Duolang sheep using rumen metagenomic and muscle metabolomic analyses across different age groups. A total of 24 three-month-old male Duolang sheep were selected and reared, and samples of longissimus thoracis muscle and rumen contents were collected at 4, 6, and 8 months of age to evaluate meat quality, metabolites, rumen metagenome, and volatile fatty acids (VFAs). The results indicated that the lightness (L*_45min) and yellowness (b*_45min) of the longissimus thoracis muscle at 45 min post-slaughter were significantly higher at 4 and 6 months than at 8 months of age (p < 0.05). In terms of ruminal VFAs, butyrate concentration was significantly higher at 6 months than at 4 months (p < 0.05), and valerate concentration exhibited a quadratic relationship with age (p = 0.02). With increasing age, the relative abundances of Prevotella and Fibrobacter increased, whereas those of Methanobrevibacter and Bacteroides decreased (p < 0.05), leading to shifts in functional pathways related to amino acid, lipid, and carbohydrate and energy metabolism. Untargeted metabolomics revealed that muscle betaine and inosine peaked at 4 months of age, whereas L-arginine, L-proline, and inosinic acid were most abundant at 6 months of age (p < 0.05). Correlation analysis revealed that the b*_45min was positively associated with ruminal concentrations of propionate, butyrate, and valerate, as well as with the relative abundances of key Selenomonadales taxa (p < 0.05). Inosinic acid exhibited a positive correlation with the abundance of the genus Sodaliphilus and ruminal butyrate concentration (p < 0.05), while Sodaliphilus abundance was negatively correlated with inosine (p < 0.05). In summary, this study demonstrates that age-related variations in the meat quality of Duolang sheep are closely associated with rumen microbial ecology and muscle metabolites, offering novel insights into the molecular mechanisms underlying meat quality formation and identifying potential biomarkers.