Cattle-yak is a hybrid F₁ generation of cattle and yak, which has a history of more than 3000 years and has shown better production performance and higher economic benefits than those of yaks. However, up to now, there has been no study on the transcriptome-wide m⁶A methylation profile of bovine skeletal muscle and its potential biological function during muscle development. Here, we observed significant changes in the expression levels of muscle-related marker genes and methylation-related enzymes during the development of cattle-yak, and the overall m⁶A content in the Longissimus dorsi muscle of 18-month-old cattle-yak decreased significantly. A total of 36,602 peaks, 11,223 genes and 8388 lncRNAs were identified in the two groups, including 2989 differential peaks (427 up-regulated peaks and 2562 down-regulated peaks), 1457 differentially expressed genes (833 up-regulated genes and 624 down-regulated genes) and 857 differentially expressed lncRNAs (293 up-regulated lncRNAs and 564 down-regulated lncRNAs). GO and KEGG analysis revealed that they were significantly enriched in some muscle-related pathways (Wnt signaling pathway and MAPK signaling pathway) and high-altitude adaptation-related pathway (HIF-1 signaling pathway). Moreover, m⁶A abundance was positively correlated with gene expression levels, while it was negatively correlated with lncRNA expression levels. This indicates that m⁶A modification played an important role in the Longissimus dorsi muscle development of cattle-yak; however, the regulation mechanism of m⁶A-modified mRNA and lncRNA may be different. This study was the first report of transcriptome-wide m⁶A-modified mRNAs and lncRNAs atlas in the Longissimus dorsi muscle development of cattle-yak, one which will provide new perspectives for genetic improvement in bovines.

Long-haired individuals in the Tianzhu white yak population are a unique genetic resource, and have important landscape value. Copy number variation (CNV) is an important source of phenotypic variation in mammals. In this study, we used resequencing technology to detect the whole genome of 10 long-haired Tianzhu white yaks (LTWY) and 10 normal-haired Tianzhu white yaks (NTWY), and analyzed the differences of CNV in the genome of LTWYs and NTWYs. A total of 110268 CNVs were identified, 2006 CNVRs were defined, and the distribution map of these CNVRs on chromosomes was constructed. The comparison of LTWYs and NTWYs identified 80 differential CNVR-harbored genes, which were enriched in lipid metabolism, cell migration and other functions. Notably, some differential genes were identified as associated with hair growth and hair-follicle development (e.g., ASTN2, ATM, COL22A1, GK5, SLIT3, PM20D1, and SGCZ). In general, we present the first genome-wide analysis of CNV in LTWYs and NTWYs. Our results can provide new insights into the phenotypic variation of different hair lengths in Tianzhu white yaks.

Understanding animal growth plays an important role in improving animal genetics and breeding. In order to explore the early growth and development law of Ashidan yak, the body weight (BW), wither height (WH), body oblique length (BL) and chest girth (CG) of 260 female Ashidan yaks were measured. These individuals grew under grazing conditions, and growth traits were measured at 6, 12, 18 and 30 months of age. Then the absolute growth and relative growth of Ashidan yak were calculated, and five nonlinear models (Logistic model, Gompertz model, Brody model, von Bertalanffy model and Richards model) were used to fit the growth curve of Ashidan yak. The fitting effect of the model was evaluated according to MSE, AIC and BIC. The results showed that the growth rate of Ashidan yak was the fastest from 12 to 18 months old, and the growth was slow or even stagnant from 6 to 12 months old. The AIC and BIC values of the Richards model were the lowest among the five models, with an AIC value of 4543.98 and a BIC value of 4563.19. The Richards model estimated body weight at 155.642 kg. In summary, the growth rate of female Ashidan yak changes with the seasons, growing faster in warm seasons and slower in cold seasons. Richards model is the best model to describe the growth curve of female Ashidan yak in five nonlinear models.

Intramuscular fat content is a key factor in determining the quality and value of beef. Intramuscular adipocytes and satellite cells can interact with each other, and both are the source cells for intramuscular fat formation. To better understand the mechanism of bovine adipocytes regulating adipogenic transdifferentiation of muscle satellite cells (MSCs), this study established a co-culture system of bovine adipocytes and bovine MSCs, identified and isolated exosomes secreted by bovine adipocytes, co-cultured exosomes with bovine MSCs, and performed lncRNA sequencing of exosomes. The results showed that lipid droplets appeared in bovine MSCs under the co-culture system, and the expression levels of the PPARγ and CEBPA, which were lipogenesis-related genes, were significantly elevated. In addition, this study identified 3425 lncRNAs in adipocyte-derived exosomes, and the target genes of these lncRNAs were significantly enriched in gene functions and pathways related to transcriptional regulation, cellular differentiation, lipogenesis, and metabolism. It is worth noting that lncRNA-DGAT2 (lncDGAT2) can competitively bind to bta-miR-2455, increase the expression of target gene DGAT2, and promote adipogenic transdifferentiation of MSCs. In summary, bovine adipocytes can regulate the adipogenic transdifferentiation of MSCs through exosomes and exosomal lncRNAs. This study provides new insights into the regulation mechanism of bovine intramuscular fat deposition.

Lactation is a complex physiological process regulated by numerous genes and factors. Circular RNA (circRNA), a non-coding RNA, acts as a molecular sponge that sequesters microRNAs (miRNAs) to regulate target gene expression. Although circRNA has been linked to mammary gland lactation, its specific role in yaks remains underexplored. This study employed circular RNA sequencing (circRNA-seq) to examine the differential expression of circRNAs in yak mammary tissues during lactation and the dry period. Additionally, an enrichment analysis of the differentially expressed circRNAs (DECs) was performed. A competing endogenous RNA (ceRNA) network was then constructed to explore the potential of their roles in lactation and mammary gland development. We detected 18,905 circRNAs in yak mammary tissue, among which 302 showed differential expression. The host genes of these DECs were enriched in functions and pathways associated with yak milk synthesis and composition. Through the construction of a ceRNA network and the enrichment analysis of associated mRNAs, this study identified ceRNAs potentially involved in regulating lactation and mammary gland development. In conclusion, circRNAs in yak mammary tissues were identified and analyzed across lactation and dry periods, establishing a ceRNA network related to lactation regulation. These findings provide novel insights into the regulatory mechanisms governing lactation in yaks (Bos grunniens).

Yanhuang cattle is a specialized beef breed independently developed in China with high economic value. However, the effects of the horned/polled trait on its production performance and the underlying genetic markers are poorly understood. This study aimed to evaluate the impact of horn status and to validate candidate genetic markers for the polled trait in this breed. A total of 60 Yanhuang cattle (30 horned and 30 polled) were used for comparative analysis of growth, carcass, and meat quality traits. Additionally, blood samples from 200 individuals (100 horned and 100 polled) were collected for molecular screening of seven candidate genetic markers previously associated with polledness in cattle. The polled cattle showed significantly higher body weight from 12 months onward. Body height and hip height were significantly greater at 12, 18, and 24 months, while body length displayed significant advantages at 6, 18, 24, and 30 months. Polled cattle also outperformed in chest girth (18 months), abdominal circumference (significant at 18–30 months), and ischial end width (significant at 6–12 months). Regarding slaughter traits, polled cattle exhibited higher carcass weight, along with significantly improved slaughter and net meat rates, though no differences were observed in meat quality. At the molecular level, the P_202ID indel marker was successfully validated in the polled Yanhuang population. Our findings demonstrate that the polled trait is associated with superior production performance in Yanhuang cattle, and the P_202ID marker represents a reliable molecular tool for polled selection, providing a theoretical and technical basis for the genetic improvement and breeding of this breed.