The objective of this study was to explore the genetic parameters of conformation traits and milk production traits in Chinese Holstein cattle and to provide a reference for dairy cattle breeding. We collected the phenotypic data of 23 conformation traits and five milk production traits of Chinese Holsteins and used animal models to estimate the genetic parameters of conformation traits and milk production traits. The estimated heritability of conformation traits ranged from 0.11 (angularity) to 0.37 (heel depth) and the genetic correlation between conformation traits ranged from −0.73 (bone quality and rear leg-rear view) to 0.76 (chest width and loin strength). The heritability of milk production traits ranged from 0.23 (somatic cell score) to 0.50 (305-d milk yield). The estimated values of genetic correlation between conformation traits and milk production traits ranged from −0.56 (heel depth and 305-d milk yield) to 0.57 (udder texture and milk fat percentage). There was a positive genetic correlation between most conformation traits and milk fat percentage, but a weak negative genetic correlation with milk yield. Strengthening the moderately and highly heritable milk production and conformation traits, especially the selection of rear udder traits and body shape total score, will be beneficial in improving the performance of dairy cows.

In this study, we examined correlations between the deposition of inosine monophosphate (IMP) and mRNA expression of the adenylate kinase 1 (AK1) gene in Jingyuan chicken. The IMP content was determined by high-performance liquid chromatography. Transcriptome sequencing was used to screen the differentially expressed gene AK1 and real-time quantitative polymerase chain reaction (PCR) to determine the expression level of AK1 mRNA associated with IMP synthesis. IMP and inosine content in the breast muscles of both Jingyuan cocks and hens was found to be significantly higher than that in the leg muscles. Similarly, the expression of AK1 mRNA in the breast muscles of cocks and hens was significantly higher than that in the leg muscles. Moreover, AK1 mRNA expression in cock breast muscles was negatively correlated with IMP content, whereas its expression in cock leg muscles was positively correlated with IMP content. In contrast, the expression of AK1 mRNA in hen breast and leg muscles was significantly positively correlated with IMP content. These findings provide a scientific basis for enhancing the meat flavor of Jingyuan chicken and promoting the development and utilization of local variety resources, as well as constituting a basis for screening IMP-regulated genes. Our study will advance our current understanding of AK1 function.

Currently, the identification of valuable candidate genes affecting milk fat synthesis in dairy cows is still limited, and the specific regulatory mechanism is still unknown. In this study, we used primary bovine mammary epithelial cells(BMECs)as a model and utilized overexpression and knockdown techniques for the PI4K2A gene to investigate the specific mechanisms by which it regulates lipid metabolism in BMECs. We studied whether PI4K2A regulates the inhibition of trans-10, cis-12 conjugated linoleic acid (t10,c12-CLA) on lipid synthesis in BMECs. The results revealed that PI4K2A plays a crucial regulatory role within the cytoplasm of BMECs, positively impacting fatty acid (FA) transport, triacylglycerol (TAG) synthesis, and lipid droplet secretion (p < 0.05 for all effects). Furthermore, PI4K2A promotes cell proliferation and inhibits apoptosis (p < 0.05). This study also confirmed that overexpressing the PI4K2A gene can effectively reduce the inhibitory effect of t10,c12-CLA on lipid synthesis in BMECs. Our findings have deepened the understanding of the regulatory mechanisms of milk fat synthesis and provide potential genetic targets for the improvement of lactation traits in dairy cows.

With growing demand for animal protein and increasing pressure on conventional feed resources, Tenebrio molitor ( T. molitor ) has emerged as a promising alternative protein source due to its high protein content, favorable fatty acid profile, efficient production, and ability to valorize agricultural by-products. This review summarizes the biological and nutritional characteristics of T. molitor , together with the rearing and processing factors affecting its suitability for animal feeding, with particular emphasis on its potential use in ruminant diets. Current evidence indicates that T. molitor larvae, the main form used in feed, have relatively low chitin content and generally good palatability and digestibility. Their nutritional value is influenced by rearing substrate, stocking density, and environmental conditions. Processing methods such as defatting, fermentation, enzymatic hydrolysis, and high hydrostatic pressure may improve nutrient availability and reduce limitations associated with lipid content and chitin. In vitro studies suggest that T. molitor meal can modulate rumen fermentation, with potential benefits for methane reduction, rumen-undegradable protein supply, and post-ruminal nutrient digestibility. However, in vivo evidence remains scarce, and its effects on animal performance are not yet fully understood. Large-scale application is further constrained by safety concerns, regulatory heterogeneity, market acceptance, and cost. Future studies integrating multi-omics, techno-economic analysis, and life cycle assessment are needed to clarify its nutritional, physiological, and environmental impacts and to support standardized production and safety evaluation.

The objectives of this study were to estimate genetic parameters for stayability in Chinese Holstein cattle and to estimate its genetic correlations with routinely collected traits. Although knowledge and genetic breeding technologies for dairy cattle have advanced, the lifespan of dairy cows has been declining, mainly due to increased production stress and associated health problems. This makes the genetic improvement of Holstein cattle crucial for sustainable production. Stayability is an indicator trait reflecting longevity, measured as the survival probability of dairy cows at specific stages. To evaluate temporal differences in herd retention, we defined 7 stayability traits as the ability of cows to remain in the herd for 36 (S36), 42 (S42), 48 (S48), 54 (S54), 60 (S60), 72 (S72), and 84 (S84) months after first calving. Data from 56,630 cows between 2011 and 2020 across 14 dairy farms in Ningxia were considered for stayability analyses. Survival analysis using non-parametric methods showed that cattle with sterility had the longest survival time, while those with abomasal displacement had the shortest survival time. The heritability estimates (±standard error) for S36, S42, S48, S54, S60, S72 and S84 were 0.048 ± 0.006, 0.063 ± 0.006, 0.074 ± 0.007, 0.099 ± 0.007, 0.115 ± 0.007, 0.088 ± 0.007, 0.118 ± 0.008, respectively. The genetic and phenotypic correlations among stayability traits ranged from 0.382 to 0.975 and from 0.090 to 0.799, respectively. Furthermore, the approximate genetic correlations between stayability and routinely collected traits (8 production, 20 conformation, 13 fertility, 13 health traits) were assessed. Stayability showed low to moderate genetic correlations with most of these traits. In summary, developing a selection index that incorporates stayability is expected to improve the longevity of dairy cows. All unfavorable genetic relationships observed between stayability and other routinely collected traits should be accounted for in a selection index, thereby enhancing the lifespan of Holstein cattle while maintaining or improving productive performance.

Lactation traits are important indicators for evaluating the production performance of dairy cows and the economic efficiency of dairy production. Identifying potential regulatory genes is essential for elucidating the molecular mechanisms underlying lactation and facilitating molecular breeding. This study aimed to identify candidate genes and regulatory pathways potentially associated with lactation traits in dairy cows by integrating transcriptome expression profiles of primary bovine mammary epithelial cells (BMECs) from eight Holstein cows with lactation phenotypic data. A gene co-expression network was constructed using weighted gene co-expression network analysis (WGCNA). Co-expression modules associated with lactation traits were identified, and candidate genes were further screened by integrating gene significance, module membership, functional enrichment analysis, random forest analysis, gene-phenotype association analysis, single-gene gene set enrichment analysis (GSEA), ROC curve analysis, and tissue expression profiling. Four co-expression modules, namely MEdarkturquoise, MEsteelblue, MEbrown, and MEskyblue3, were significantly associated with lactation traits (p < 0.05). Genes in these modules were mainly enriched in biological processes and pathways related to ribosome biogenesis, protein translation, the cell cycle, oxidative phosphorylation, and the PI3K-Akt signaling pathway, which may be involved in lactation regulation. Through multi-strategy cross-screening, four candidate genes were ultimately identified. MDM2 was associated with daily milk yield (DYM), RPL37A with total milk solids (TMS), and SLC25A25 and CCNE2 with milk fat percentage (MFP) and fat-to-protein percentage ratio (FPP). Reverse transcription quantitative real-time PCR (RT-qPCR) validation showed that MDM2 and RPL37A were relatively highly expressed in mammary tissue, suggesting that they may be involved in lactation-related biological processes in dairy cows. These findings provide potential candidate regulators and theoretical support for further studies on the molecular mechanisms of lactation traits; however, their functional roles require further validation through in vitro and in vivo experiments.