Body weight is an important economic trait for sheep and it is vital for their successful production and breeding. Therefore, identifying the genomic regions and biological pathways that contribute to understanding variability in body weight traits is significant for selection purposes. In this study, the genome-wide associations of birth, weaning, yearling, and adult weights of 460 fine-wool sheep were determined using resequencing technology. The results showed that 113 single nucleotide polymorphisms (SNPs) reached the genome-wide significance levels for the four body weight traits and 30 genes were annotated effectively, including AADACL3, VGF, NPC1, and SERPINA12. The genes annotated by these SNPs significantly enriched 78 gene ontology terms and 25 signaling pathways, and were found to mainly participate in skeletal muscle development and lipid metabolism. These genes can be used as candidate genes for body weight in sheep, and provide useful information for the production and genomic selection of Chinese fine-wool sheep.

Tibetan goat is an ancient breed, which inhabits the adverse conditions of the plateaus in China. To investigate the role of selection in shaping its genomes, we genotyped Tibetan goats (Nagqu Prefecture, above 4500 m) and three lowland populations (Xinjiang goats, Taihang goats and Huanghuai goats). The result of PCA, neighbor-joining (N-J) tree and model-based clustering showed that the genetic structure between the Tibetan goat and the three lowland populations has significant difference. As demonstrated by the di statistic, we found that some genes were related to the high-altitude adaptation of Tibetan goats. Functional analysis revealed that these genes were enriched in the VEGF (vascular endothelial growth factor) signaling pathway and melanoma, suggesting that nine genes (FGF2, EGFR, AKT1, PTEN, MITF, ENPEP, SIRT6, KDR, and CDC42) might have important roles in the high-altitude adaptation of Nagqu Tibetan goats. We also found that the LEPR gene was under the strongest selection (di value = 16.70), and it could induce upregulation of the hypoxic ventilatory response. In addition, five genes (LEPR, LDB1, EGFR, NOX4 and FGF2) with high di values were analyzed using q-PCR. Among them, we found that LEPR, LDB1 and FGF2 exhibited higher expression in the lungs of the Tibetan goats; LEPR, EGFR and LDB1 exhibited higher expression in the hearts of the Huanghuai goat. Our results suggest that LEPR, LDB1, EGFR and FGF2 genes may be related to the high-altitude adaptation of the goats. These findings improve our understanding of the selection of the high-altitude adaptability of the Nagqu Tibetan goats and provide new theoretical knowledge for the conservation and utilization of germplasm resources.

With the intensive development of the sheep industry and increasing global temperatures, heat stress in sheep has become an increasingly severe and important issue in recent years. The level of N⁶-methyladenosine (m⁶A) RNA methylation changes in response to stress plays important roles in stress responses. However, the role of m⁶A in the heat stress response of sheep remains unclear. To explore this issue, we measured heat stress protein (HSP) expression, liver function indexes, m⁶A on RNA, m⁶A-related enzyme expression, and tissue damage in sheep that had been subjected to heat stress. At the transcriptome level, our results showed significant increases in m⁶A on RNA and increased mRNA levels of HSPs (HSP70, HSP90, and HSP110) and m⁶A-related enzymes [METTL3 (methyltransferase-like 3), METTL14 (methyltransferase-like 14), WTAP (wilms tumor 1-associated protein), FTO (fat mass and obesity-associated protein), ALKBH5 (alkB homologue 5), YTHDF1-3 (YTH domain family proteins), and YTHDC1-2 (YTH domain-containing proteins)] following heat stress. At the protein level, the expression of METTL3, YTHDF1-2, and YTHDC2 showed no significant differences following heat stress. However, in contrast to its mRNA level after heat stress, the protein expression of YTHDF3 was reduced, while the expression of HSPs (HSP70, HSP90, and HSP110), METTL14, WTAP, FTO, ALKBH5, YTHDF3, and YTHDC1 increased in line with their measured mRNA levels. Histological experiments revealed that heat stress caused varying degrees of damage to sheep liver tissue. Moreover, immunohistochemical staining indicated that the m⁶A-related enzymes were expressed in sheep hepatocytes, and differences in expression patterns were observed between the control and heat stress groups. In summary, differences in the level of m⁶A and the expression of m⁶A-related enzymes in the liver of sheep were observed after heat stress. This indicates that m⁶A is involved in the regulation of heat stress in sheep. Our findings provide a new avenue for studying the responses to heat stress in sheep.

Inner Mongolia and Liaoning cashmere goats in China are well-known for their cashmere quality and yield. Thus, they are great models for identifying genomic regions associated with cashmere traits. Herein, 53 Inner Mongolia cashmere goats, Liaoning cashmere goats and Huanghuai goats were genotyped, and 53,347 single-nucleotide polymorphisms (SNPs) were produced using the Illumina Caprine 50K SNP chip. Additionally, we identified some positively selected SNPs by analyzing Fst and XP-EHH. The top 5% of SNPs had selection signatures. After gene annotation, 222 and 173 candidate genes were identified in Inner Mongolia and Liaoning cashmere goats, respectively. Several genes were related to hair follicle development, such as TRPS1, WDR74, LRRC14, SPTLC3, IGF1R, PADI2, FOXP1, WNT10A and CSN3. Gene enrichment analysis of these cashmere trait-associated genes related 67 enriched signaling pathways that mainly participate in hair follicle development and stem cell pluripotency regulation. Furthermore, we identified 20 overlapping genes that were selected in both cashmere goat breeds. Among these overlapping genes, WNT10A and CSN3, which are associated with hair follicle development, are potentially involved in cashmere production. These findings may improve molecular breeding of cashmere goats in the future.

Crossbreeding improves and enhances meat quality and is widely used in sheep production; however, the molecular mechanisms underlying the meat quality of various crossbred sheep remain unknown. In this study, male Southdown, Suffolk and Hu sheep were crossbred with female Hu sheep, and the transcriptomes and metabolomes of the longissimus dorsi muscle of the F1 generation were sequenced to explore how different sire breeds affect meat quality. The results showed that 631 differentially expressed genes and 119 significantly altered metabolites contributed to muscle development characteristics and meat quality-related diversity (P < 0.05). These genes and metabolites were significantly enriched in lipid metabolism pathways, including arachidonic acid metabolism and PPAR signaling. Several candidate genes were associated with muscle growth, such as MYLK3, MYL10, FIGN, MYH8, MYOM3, LMCD1, and FLRT1. Among these, MYH8 and MYL10 participated in regulating muscle growth and development and were correlated with meat quality-related fatty acid levels (|r| > 0.5 and p < 0.05). We selected mRNA from four of these genes to verify the accuracy of the sequencing data via qRT-PCR. Our findings provide further insight into the key genes and metabolites involved in muscle growth and meat quality in hybrid sheep populations.