A Study on the Mechanism of N-Carbamylglutamate’s (NCG) Effects on the Liver Transcriptome and Metabolism of Cold-Stressed Mongolian Ewes and Fetuses

Chronic cold stress disrupts hepatic metabolism and fetal development of Mongolian sheep in northern pastoral zones, while systematic nutritional mitigation strategies remain poorly characterized. N-carbamylglutamate (NCG) promotes endogenous arginine synthesis; however, its hepatic regulatory roles against cold stress in pregnant ewes and fetuses remain unclear. This study explored the potential protective effects of NCG via integrated hepatic transcriptome and metabolome analysis. Twenty-four late-gestation ewes were assigned to warm control, cold stress, and cold stress + NCG supplementation groups. Hepatic mRNA, lncRNA, circRNA, and miRNA sequencing, untargeted LC-MS metabolomics, multi-omics conjoint analysis, and qRT-PCR verification were performed using ewe and fetal liver tissues. The results indicated that cold stress potentially was associated with mTOR, PI3K/AKT, amino acid, and energy metabolic pathways, inducing extensive transcriptomic and metabolic alterations. NCG supplementation might reverse cold-induced transcriptional and metabolic disorders and restore glutathione and cysteine–methionine metabolism. qRT-PCR validated the differential expression of core hub genes AK4, AHCY, and RRM2, linking transcriptomic and metabolic reprogramming. Divergent hepatic molecular responses to NCG were observed between ewes and fetuses. Multi-omics correlation analysis suggested that maternal NCG may modulate hepatic energy and amino acid metabolism through mTOR and redox-related pathways under cold stress and potentially exert transgenerational hepatic effects on fetuses. These findings provide preliminary omics-based mechanistic hypotheses and a theoretical basis for nutritional intervention against cold stress in sheep production.