(1) Background: The Hu sheep is a renowned breed characterized by high reproduction, year-round estrus, and resistance to high humidity and temperature conditions. However, the breed exhibits lower growth rates and meat yields, which necessitate improvements through selective breeding. The integration of molecular markers in sheep breeding programs has the potential to enhance growth performance, reduce breeding cycles, and increase meat production. Currently, the applications of SNP chips for genotyping in conjunction with genome-wide association studies (GWAS) have become a prevalent approach for identifying candidate genes associated with economically significant traits in livestock. (2) Methods: To pinpoint candidate genes influencing growth traits in Hu sheep, we recorded the birth weight, weaning weight, and weights at 3, 4, 5, 6, and 7 months for a total of 567 Hu sheep, and genotyping was performed using the Ovine 40K SNP chip. (3) Results: Through GWAS analysis and KEGG pathway enrichment, we identified three candidate genes associated with birth weight (CAMK2B, CACNA2D1, and CACNA1C). Additionally, we found two candidate genes linked to weaning weight (FGF9 and BMPR1B), with CACNA2D1 also serving as a shared gene between birth weight and weaning weight traits. Furthermore, we identified eight candidate genes related to monthly weight (FIGF, WT1, KCNIP4, JAK2, WWP1, PLCL1, GPRIN3, and CCSER1). (4) Conclusion: Our findings revealed a total of 13 candidate genetic markers that can be utilized for molecular marker-assisted selection, aiming to improve meat production in sheep breeding programs.

Most sheep are seasonal estrus, and they breed in autumn when the days get shorter. Seasonal estrus is an important factor that affects the productivity and fertility of sheep. The key point to solve this problem is to explore the regulation mechanism of estrus in sheep. Therefore, in this study, transcriptomic sequencing technology was used to identify differentially expressed mRNAs in the hypothalamus, pituitary and ovary of Small Tail Han sheep (year-round estrus) and tan sheep (seasonal estrus) among luteal, proestrus and estrus stages. There were 256,923,304,156 mRNAs being identified in the hypothalamus, pituitary and ovary, respectively. Functional analysis showed that the photosensor, leucine and isoleucine biosynthesis pathways were enriched significantly. It is speculated that photoperiod may initiate estrus by stimulating the corresponding pathways in hypothalamus. ODC1, PRLH, CRYBB2, SMAD5, OPN1SW, TPH1 are believed to be key genes involved in the estrogen process. In conclusion, this study expanded the database of indigenous sheep breeds, and also provided new candidate genes for future genetic and molecular studies on the seasonal estrus trait in sheep.

Hu sheep are renowned for their adaptation to high‐temperature, humid environments and their high fecundity. Despite serving as the founder species for sheep breeding in China, the genetic mechanisms underlying these desirable traits and the breed's origin have remained unresolved. To address the longstanding challenges in understanding their adaptations and origins, comprehensive analyses utilizing genetic data is conducted from over 300 Hu sheep and ≈200 other Chinese native sheep. The study unveils the migration history of sheep and the formation of the Hu sheep in eastern China. By employing multiple screening methods, this study identifies that the BMPR1B , UNC5C , and GRID2 synergistically contribute to the high fecundity trait in Hu sheep. The coexistence of beneficial genotypes in these genes increase the likelihood of multiple births. Notably, the results suggest a potential coevolution between environmental adaptation and reproductive traits in this breed. Overall, the study provides novel insights into the genetic origin and adaptation of Hu sheep, offering new perspectives for molecular breeding in sheep and other livestock species.

(1) Background: Litter size is one of the most important economic traits of sheep. The FecB locus has been extensively studied due to its significant impact on litter size in Hu sheep, and BMP15 and GDF9 have also been reported as major genes associated with litter size in sheep. This study aimed to identify variants of BMP15 and GDF9 and perform an association analysis of these variants with litter size in the Hu sheep breed. (2) Methods: In this study, exons of the BMP15 and GDF9 genes were fully sequenced to identify polymorphisms in Hu sheep. Population genetic parameters and haplotype frequencies were estimated, and an association analysis between these polymorphic loci and litter size was performed. Additionally, the protein structures of the wild-type and mutated BMP15 and GDF9 genes were predicted. (3) Results: The polymorphisms of the BMP15 and GDF9 genes were investigated within their exon regions, revealing mutations at four previously reported sites: BMP15 c.31_33CTTdel and GDF9 (G2, G3, and G4) in Hu sheep, with no novel variants were detected. Genetic analysis indicated that the GDF9-G3 and GDF9-G4 loci have low polymorphisms, whereas the BMP15 c.31_33CTTdel and the GDF9-G2 locus are moderately polymorphic. The mutation sites in the BMP15 and GDF9 genes were under Hardy–Weinberg equilibrium. Association analysis revealed that the BMP15 c.31_33CTTdel and GDF9 (G2, G3, and G4) mutations are not associated with litter size in Hu sheep. Protein structure prediction indicated that the mutations in BMP15 and GDF9 resulted in alterations to their tertiary structures. (4) Conclusions: In this study, four reported mutations in the BMP15 and GDF9 genes can also be detected in the Hu sheep breed. In these mutations, the G2 and G3 mutations of GDF9 did not alter the amino acid sequence, while the BMP15 c.31_33CTTdel mutation and the GDF9 G4 mutation resulted in protein structure alteration. Furthermore, the BMP15 c.31_33CTTdel mutation and the GDF9 mutations (G2, G3, G4) were associated with an increased tendency in litter size. However, no significant difference was observed (p > 0.05). This study provides valuable insights for improving the lambing performance of Hu sheep.

Pituitary pars tuberalis (PT) plays an important role as the transmission center in the seasonal reproduction of animals. It helps convert external photoperiod signals into intrinsic seasonal reproduction signals. In sheep PT, specific expression patterns of several genes (including short photoperiod-induced gene CHGA and long photoperiod genes EYA3 and TSHβ) under different photoperiods are crucial characteristics during this signal transduction. Recent studies have revealed the role of epigenetics in regulating the expression of seasonal reproductive key genes. Therefore, we explored whether microRNAs and LncRNAs regulated the expressions of the above key genes. Firstly, the expression of miR-25 and CHGA showed a significant negative correlation in sheep PT. Results of the dual luciferase reporter assay and miR-25 overexpression indicated that miR-25 could inhibit the expression of CHGA by specifically binding to its 3′UTR region in pituitary cells. Then, expression negative correlation and dual luciferase reporter analyses were used to screen and identify the candidate LncRNA (Lnc107153) targeted by miR-25. Finally, the results of fluorescence in situ hybridization and Lnc107153 overexpression suggested that Lnc107153 and miR-25 were involved in the epigenetic regulation of CHGA expression. However, the expressions of EYA3 and TSHβ were not regulated by miRNAs. These results will provide new insights into the epigenetic regulatory network of key genes in sheep seasonal reproduction.

(1) Background: The Hulunbuir sheep is a Chinese local sheep breed with good meat quality and exceptional cold-stress resilience. However, the growth performance of the Hulunbuir sheep is lower when compared to that of commercial breeds. Growth traits such as body weight and body size are critical, as they directly influence the meat production in sheep farming. Employing genome-wide association studies can identify SNPs and candidate genes related to growth traits in Hulunbuir sheep. (2) Methods: The chest girth (CG), cannon circumference (CC), hip width (HW), body height (BH), and body length (BL) of 799 Hulunbuir sheep were measured. All the animals were divided into three groups according to their age (Group 1: 0–6 months old, Group 2: 12–24 months old, Group 3: 48–70 months old). Subsequently, genotyping was carried out using the Sheep 40K liquid chip. A multi-trait genome-wide association study (MT-GWAS) was performed for each group of animals. (3) Results: A total of three candidate genes (SLC9C1, VSTM2A, FRG1) associated with body size traits were identified through GWAS analysis and KEGG pathway enrichment for Group 2. (4) Conclusions: This study identified three candidate genes related to body size in Hulunbuir sheep, providing genetic targets for marker-assisted selection (MAS) in Hulunbuir sheep.