The development of secondary hair follicles influences the quality of sheep wool. However, the mechanism by which proteins mediate the fetal development of secondary hair follicles remains unknown. In this study, the histomorphology of secondary hair follicles was analyzed over four stages of fetal development (75, 85, 95, and 105 gestational days). TMT-based quantitative proteomics was used to compare the differential protein profiles of skin tissues between consecutive developmental periods (75 versus 85, 85 versus 95, and 95 versus 105 gestational days). We found that the density of secondary hair follicles and the secondary hair follicles/primary hair follicles ratio increased from 85 to 105 gestational days. Bioinformatic analysis identified 238, 35, and 348 differentially expressed proteins in the respective comparison periods. Focal adhesion, ECM−receptor interaction, and the estrogen signaling pathway all played important roles in secondary hair follicle development. COL1A1, THBS3, ITGA6, COL6A1, and THBS4 were identified as potential candidate proteins in the initiation of secondary hair follicles. This study provides valuable proteomics data on secondary hair follicle development and thus has deepened our understanding of the molecular mechanisms underlying wool quality traits in fine-wool sheep.

This study sought to investigate the impact of different levels of dietary maintenance energy metabolism on nutrient digestibility, rumen microbiota composition, and serum biochemical parameters in Lanzhou fat-tailed sheep rams. A total of twenty rams, each aged eight months and with an initial mean body weight of 27.81 ± 3.38 kg, were selected and randomly assigned to one of four experimental groups. These groups were administered with different levels of metabolizable energy (MEM): low energy (LE), intermediate energy (IE), high energy (HE), and extra high energy (EHE), corresponding to 6.77, 7.22, 7.72, and 8.20 MJ/d, respectively. The results showed a linear increase (p < 0.001) in average daily gain (ADG), dry matter (DM) intake, apparent DM digestibility, and crude protein (CP) digestibility. Conversely, the intake of nitrogen (NI), fecal nitrogen (FN), and manure nitrogen (MN) exhibited a significant linear decrease (p < 0.001). The N utilization efficiency rations of FN/NI and MN/NI linearly decreased (p < 0.001), while RN/NI linearly increased (p < 0.001). Additionally, the intake of gross energy (GE), methane energy (CH4-E), digestible energy (DE), and metabolizable energy (ME) exhibited a linear increase, whereas the ration of FE/GE intake linearly decreased (p < 0.001). The efficiency of energy utilization expressed as a proportion of GE intake (DE/GE intake, ME/GE intake, ME/DE intake, and CH4-E/GE intake) showed linear alterations (p < 0.05) with the increase in the dietary energy supplementation level. The dietary energy level did not exert a significant impact on serum biochemical indices (p > 0.05). At the phylum level, the average abundances of Verrucomicrobiota were significantly reduced in the EHE group compared to the IE group, while the average abundances of Desulfobacterota were significantly lower in the EHE group relative to the LE group. At the genus level, the average abundances of Succiniclasticum were significantly higher in the HE and EHE groups compared to the LE group. In conclusion, the energy level (8.20 MJ/d) significantly enhanced nutrient digestibility, energy, and nitrogen metabolism, and it significantly increased the relative abundances of Succiniclasticum.

Excessive adipose tissue accumulation in sheep disrupts insulin signaling, inducing insulin resistance, and alters energy partitioning mechanisms. These changes adversely affect both ovine health and production efficiency. This study employed whole-genome resequencing to conduct selection signal analysis in long-fat-tailed (Lanzhou fat-tailed sheep) and short-fat-tailed (Hu sheep) breeds, investigating the genetic basis underlying divergent lipid metabolism-related traits between these distinct tail phenotypes. Fifteen healthy adult individuals, each from long-fat-tailed (Lanzhou Large-tailed sheep) and short-fat-tailed (Hu sheep) breeds, underwent whole-genome resequencing. Whole-genome resequencing analyses via F_ST, XP-CLR, and XP-EHH identified 75 significantly selected regions (p < 0.01), revealing eight key candidate genes (DAB1, DPP10, EPHA6, GPC5, KLF12, PAK7, PTPN3, TENM3). Subsequent functional enrichment analysis demonstrated significant enrichment of DAB1 and GPC5 in lipid metabolic processes (GO:0006629). Employing whole-genome resequencing-based selection signal analysis in long-fat-tailed (Lanzhou Large-tailed sheep) and short-fat-tailed (Hu sheep) breeds, this study identified two key lipid metabolism-associated genes (DAB1 and GPC5). These findings provide critical insights for conserving genetic resources and informing molecular breeding strategies targeting divergent tail phenotypes.

Placentation and placental steroidogenesis are important for pregnancy and maternal–fetal health. As pregnancy progresses, the main site of progesterone (P4) synthesis changes from the corpus luteum to the placenta, in which placental trophoblasts are the main cell type for P4 synthesis. Therefore, this study investigated the effects of P4 on apoptosis and steroidogenesis in porcine placental trophoblasts and the underlying molecular mechanisms. Porcine placental trophoblasts were treated with different concentrations of P4 for 48 h in a serum-free medium in vitro. Cell number, steroidogenesis, and relevant gene and protein expression levels were detected. A high dose of P4 (10.0 μM) significantly increased P4 (p < 0.01), androstenedione (p < 0.05), testosterone (p < 0.05), and estradiol (p < 0.05) production in porcine placental trophoblasts compared with that in control cells, while a low dose of P4 (1 × 10⁻³ μΜ) had no marked impact on steroid production. The mRNA expression of apoptosis-related genes (CASP3, CASP8, and Bax) (p < 0.05) and steroidogenesis-related genes (CYP11A1, CYP19A1, and StAR) (p < 0.01) was upregulated, and the expression of HSD3B and HSD17B4 was inhibited (p < 0.05) in the porcine placental trophoblasts treated with high doses of P4. Low doses of P4 had a lighter effect on gene expression than high doses. The expression of apoptosis-related proteins CASP3 (p < 0.05), and Bax (p < 0.01) and steroidogenesis-related proteins CYP19A1 (p < 0.05) and StAR (p < 0.01) was raised, but the proliferation-related protein CCND2 (p < 0.01) was downregulated in the pTr cells treated with high dose of P4. In comparison, a low dose of P4 inhibited the expression of Bax, CYP11A1 (all p < 0.01), and CCND2 (p < 0.05), but the expression of CASP3 (p < 0.05) and StAR (p < 0.01) was upregulated. In summary, excessive P4 can induce the apoptosis of porcine placental trophoblasts and lead to abnormal steroidogenesis in the placenta and hormone imbalance.