Background: Dietary crude protein (CP) acts as a key nutritional factor that affects the growth performance and liver metabolism of fattening Hu sheep, with metabolizable energy (ME) representing a major confounding factor in CP-related responses. To isolate the specific effects of CP on liver metabolism and minimize energy–protein interactions, we standardized dietary ME at 9.4 MJ/kg dry matter. Methods: We then established three isoenergetic CP concentrations: 11.07%, 13.07%, and 15.11%. A total of ninety 4-month-old male Hu sheep (with an initial body weight of 27.09 ± 1.83 kg) were allocated at random to three dietary treatment groups, each containing 30 animals distributed across three replicate pens, and fed pelleted total mixed rations (PTMRs) for 75 days under pen conditions in southern Xinjiang. Exploratory combined transcriptomic and metabolomic profiling of liver tissue was conducted to characterize how graded CP levels modulate growth traits and hepatic metabolic pathways, thereby identifying the appropriate dietary CP level for efficient and sustainable fattening of Hu sheep in this region. Result: Results indicated that animals fed the 15.11% CP diet showed a significantly higher average daily gain (ADG) and cumulative weight gain compared with those fed 11.07% or 13.07% CP (p < 0.05). Exploratory multi-omics enrichment analysis demonstrated significant overrepresentation (p < 0.05) of differentially expressed genes and metabolites in key biological pathways—including bile secretion, AMP-activated protein kinase (AMPK) signaling, steroid biosynthesis, peroxisome proliferator-activated receptor (PPAR) signaling, and oxidative stress-related and oxidative phosphorylation. Correlation analyses characterized two hub genes—ATP6AP1 and LOC101119853—that were significantly and negatively correlated with ADG (p < 0.05), whereas two metabolites—calcidiol and ADP—displayed significant positive relationships with ADG (p < 0.05). Pathway-level comparisons further demonstrated that both the 13.07% vs. 15.11% CP and the 11.07% vs. 15.11% CP contrasts yielded significant enrichment in AMPK signaling and steroid biosynthesis. Notably, calcidiol and ADP both declined numerically in the 13.07% vs. 15.11% CP comparison, whereas only ADP reached statistical significance in the 11.07% vs. 15.11% CP contrast. Conclusions: Collectively, under an ME level of 9.4 MJ/kg, a dietary CP concentration of 15.11% contributes to favorable growth of 4-month-old fattening Hu sheep housed in pens in southern Xinjiang. This level is associated with improved growth performance and coordinated regulation of central hepatic regulatory networks—particularly those involved in energy homeostasis and steroidogenesis—thereby supporting metabolic stability without compromising animal health or production efficiency. These findings provide a preliminary molecular basis for precision protein nutrition in Hu sheep feeding systems and offer translational insights for optimizing ruminant nutrition under arid and semi-arid environmental constraints. All correlations indicate potential associations, not causal relationships.

Chemical depilation presents a promising alternative to traditional shearing for Chinese Merino sheep, aiming to overcome issues of low efficiency and animal stress. Nonetheless, the safety of meat derived from sheep treated with this technology requires comprehensive scientific evaluation. Therefore, this study aimed to investigate the effects of CPA on wool quality, physiological and biochemical parameters, carcass traits, meat quality, fatty acids, and amino acids in sheep. Sheep were treated with different concentrations of CPA for 30 days, and slaughtering was performed at 3, 15, and 30 days post-administration. The CPA treatment (25–30 mg/kg) achieved complete defleecing and significantly increased staple and stretch lengths without affecting fiber length. At the 25 mg/kg dose, certain physiological and biochemical parameters, including mean corpuscular volume, mid-cell count, and lymphocyte percentage, recovered over time, with only short-term fluctuations observed. Moreover, treatment with 25 mg/kg CPA did not affect carcass characteristics, muscle amino acid composition, or meat quality parameters. In conclusion, this study verifies that complete wool shedding can be achieved with CPA at 25–30 mg/kg, while meat quality remains unaffected, providing a scientific basis for its adoption in dual-purpose sheep production.

To identify candidate genes associated with skin tissue responses in Hu sheep raised under different regional rearing environments and to preliminarily explore their potential relevance to low-temperature-related environmental responses, this study used 1-year-old female Hu sheep raised in Anhui and Xinjiang as the experimental animals. Skin tissues were collected from the left scapular region, and their transcriptomic profiles were characterized by integrating histological analysis, RNA sequencing (RNA-seq), differential expression analysis, functional enrichment analysis, protein–protein interaction (PPI) network construction, and RT-qPCR validation. The results showed significant differences between the two groups in body weight, body length, body height, cannon circumference, rectal temperature, and ear temperature. Hematoxylin and eosin (H&E) staining indicated that the Xinjiang group exhibited a denser distribution of hair follicles, a relatively thicker dermis, and a more compact arrangement of collagen fibers, suggesting enhanced insulation-related skin characteristics. Transcriptome sequencing identified 295 differentially expressed genes (DEGs), including 193 upregulated and 102 downregulated genes. GO and KEGG enrichment analyses showed that these DEGs were mainly involved in immune and inflammatory responses, redox processes, extracellular matrix remodeling, and lipid and energy metabolism-related pathways, with significant enrichment in cytokine–cytokine receptor interaction, the chemokine signaling pathway, the NF-κB signaling pathway, glutathione metabolism, and drug metabolism–cytochrome P450. By further integrating PPI network analysis and functional annotation, CXCL13, CCL2, FGF21, GPX3, CYP1A1, HSD11B1, CDO1, and STEAP4 were identified as candidate genes. RT-qPCR results showed that the expression trends of the selected genes were generally consistent with the RNA-seq results. Overall, this study revealed differences in phenotypic traits, skin histological structure, and transcriptomic characteristics between Hu sheep raised in different regions, providing preliminary molecular clues potentially associated with low-temperature-related environmental responses. Given the differences in geographic origin and rearing environments between the two groups, the findings should be interpreted as associative evidence of skin transcriptomic responses in Hu sheep under different environmental conditions—rather than as direct causal evidence that low temperature alone drove these transcriptomic differences.