Udder conformation traits are one of the most economic traits in dairy cows, greatly affecting animal health, milk production, and producer profitability in the dairy industry. Genetic analysis of udder structure and scores have been developed in Holstein cattle. In our research, we conducted a genome-wide association study for five udder traits, including anterior udder attachment (AUA), central suspensory ligament (CSL), posterior udder attachment height (PUAH), posterior udder attachment width (PUAW), and udder depth (UD), in which the fixed and random model circulating probability unification (FarmCPU) model was applied for the association analysis. The heritability and the standard errors of these five udder traits ranged from 0.04 ± 0.00 to 0.49 ± 0.03. Phenotype data were measured from 1000 Holstein cows, and the GeneSeek Genomic Profiler (GGP) Bovine 100 K SNP chip was used to analyze genotypic data in Holstein cattle. For GWAS analysis, 984 individual cows and 84,407 single-nucleotide polymorphisms (SNPs) remained after quality control; a total of 18 SNPs were found at the GW significant threshold (p < 5.90 × 10⁻⁷). Many candidate genes were identified within 200kb upstream or downstream of the significant SNPs, which include MGST1, MGST2, MTUS1, PRKN, STXBP6, GRID2, E2F8, CDH11, FOXP1, SLF1, TMEM117, SBF2, GC, ADGRB3, and GCLC. Pathway analysis revealed that 58 Gene Ontology (GO) terms and 18 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were enriched with adjusted p values, and these GO terms and the KEGG pathway analysis were associated with biological information, metabolism, hormonal growth, and development processes. These results could give valuable biological information for the genetic architecture of udder conformation traits in dairy Holstein cattle.

Heat stress during late gestation could affect subsequent lactation performance, resulting in damage to the immune function, health, and growth performance of calves. This study aimed to compare the effects of 33 days of summer stress (Summer group, 70.15 < THI < 74.28) with 33 days of winter during late gestation (Winter group, 57.55 < THI < 67.25) on the growth, hormones, oxidative stress, and immune function of calves. Calves (Summer, n = 28; Winter, n = 23) were separated from cows immediately after birth and fed with 2 L colostrum within 2 h and 8–10 h after birth, respectively, and weaned at 60 days of age. Bodyweight (BW) was measured at birth and weaning. Withers height (WH), body length, and chest girth were measured at birth, 30 days, and 60 days of age. The health of calves ranging in age from 1 to 7 days was recorded. Plasma interferon-γ (IFN-γ), superoxide dismutase (SOD), adrenocorticotropin (ACTH), gonadotropin-releasing hormone (GnRH), IgG, cortisol, heat shock protein 70 (Hsp70), growth hormone (GH), insulin, lipid peroxide (LPO), and tumor necrosis factor-α (TNF-α) levels were measured in calves at 0 (before colostrum feeding), 3, 7, 14, 28, and 56 days of age. The pregnancy period of the Summer group was shortened by 1.44 days. The Winter and Summer groups had the same birth weight. One week after birth, the incidence of diarrhea was 57.14% and 21.74% in Summer and Winter groups, respectively. Compared with the Winter group, TNF-α in the Summer group increased significantly before colostrum feeding. ACTH and LPO decreased significantly at 3 days of age, ACTH and TNF-α decreased significantly at 7 days of age, Hsp70 increased significantly, ACTH was significantly reduced at 14 days of age, and Hsp70 increased dramatically at 7 days of age. SOD and TNF-α increased statistically at 28 days of age, LPO decreased significantly, and IFN-γ decreased significantly at 56 days of age, while IgG and GH increased significantly. We conclude that maternal heat stress during late gestation can damage the oxidative stress and immune plasma indexes of offspring before weaning.

In this study, circular RNAs (circRNAs) from Holstein cow mammary tissues were identified and compared between early lactation and non-lactation. After analysis, 10,684 circRNAs were identified, ranging from 48 to 99,406 bp, and the average size was 882 bp. The circRNAs were mainly distributed on chromosomes 1 to 11, and 89.89% of the circRNAs belonged to sense-overlapping circRNA. The exons contained with circRNAs ranged from 1 to 47 and were concentrated from 1 to 5. Compared with the non-lactating cows, 87 circRNAs were significantly differentially expressed in the peak lactation cows. There were 68 upregulated circRNAs and 19 downregulated circRNAs. Enrichment analysis of circRNAs showed that GO analysis mainly focused on immune response, triglyceride transport, T cell receptor signaling pathway, etc. Pathway analysis mainly focused on cytokine-cytokine receptor interaction, T helper 17 cell differentiation, fatty acid biosynthesis, the JAK-STAT signaling pathway, etc. Specific primers were designed for two proximal ends of the circRNA junction sites to allow for PCR validation of four randomly selected circRNAs and carry out circRNA-miRNA interaction research. This study revealed the expression profile and characteristics of circRNAs in mammary tissue from Holstein cows at early lactation and non-lactation, thus providing rich information for the study of circRNA functions and mechanisms, as well as potential candidate miRNA genes for studying lactation in Holstein cows.

Improving the quality of milk is a challenge for zootechnicians and dairy farms across the globe. Long-chain acyl-CoA synthetase 1 (ACSL1) is a significant member of the long-chain acyl-CoA synthetase gene family. It is widely found in various organisms and influences the lactation performance of cows, including fat percentage, milk protein percentage etc. Our study was aimed to investigate the genetic effects of single nucleotide polymorphisms (SNPs) in ACSL1 on milk production traits. Twenty Chinese Holstein cows were randomly selected to extract DNA from their blood samples for PCR amplification and sequencing to identify SNPs of the bovine ACSL1 gene, and six SNPs (5’UTR-g.20523C>G, g.35446C>T, g.35651G>A, g.35827C>T, g.35941G>A and g.51472C>T) were discovered. Then, Holstein cow genotyping (n = 992) was performed by Sequenom MassARRAY based on former SNP information. Associations between SNPs and milk production traits and somatic cell score (SCS) were analyzed by the least-squares method. The results showed that SNP g.35827C>T was in high linkage disequilibrium with g.35941G>A. Significant associations were found between SNPs and test-day milk yield (TDMY), fat content (FC), protein content (PC) and SCS (p < 0.05). Among these SNPs, SNP 5’UTR-g.20523C>G showed an extremely significant effect on PC and SCS (p < 0.01). The SNP g.35446C>T showed a statistically significant effect on FC, PC, and SCS (p < 0.01), and also TDMY (p < 0.05). The SNP g.35651G>A had a statistically significant effect on PC (p < 0.01). The SNP g.35827C>T showed a highly significant effect on TDMY, FC, and SCS (p < 0.01) and significantly influenced PC (p < 0.05). Lastly, SNP g.51472C>T was significantly associated with TDMY, FC, and SCS (p < 0.05). In summary, the pleiotropic effects of bovine ACSL1 for milk production traits were found in this paper, but further investigation will be required on the intrinsic correlation to provide a theoretical basis for the research on molecular genetics of milk quality traits of Holstein cows.

Holstein and Jersey cows, as excellent dairy breeds, have their own advantages in milk yield, milk quality, disease resistance, and heat resistance. However, the adaptability and rumen microbiome changes in Holstein and Jersey cows under heat stress are not clear. Therefore, the main objective of this study was to compare the differences in heat tolerance and the changes in the ruminal microbiome in Holstein and Jersey cows under heat stress. The experiment comprised a 7-day thermo-neutral (TN) period and a 7-day heat stress (HS) period. Five Jersey cows and five Holstein cows with similar parity and days in milk were selected, and rumen fluid was collected from five of them each. Compared with the TN period, heat stress increased the respiratory rate (p < 0.05), whereas decreased the milk yield (p < 0.01) in the Holstein and Jersey cows. Also, heat stress increased the rectal temperature (p < 0.01) in the Holstein cows. Jersey cows had a significantly (p < 0.05) lower level of acetic acid, propionic acid, butyric acid, valeric acid, and TVFA during HS compared with the TN period. Furthermore, high-throughput sequencing revealed that the relative abundance of Bacteroidetes and Prevotella increased while the relative abundance of Firmicutes decreased in Holstein cows during the HS period, whereas Christensenellaceae and Clostridium were more abundant in Jersey cows during the HS period than in the TN period. Simultaneously, the dominant fungi in Holstein cows were Ascomycota, Neocallimastigomycota, and Aspergillus. Correlation analysis also provided a link between the significantly altered rumen microbiota and animal production. These results suggest that heat stress has negatively influenced the physiological parameters, milk production, and rumen microbiota of Holstein and Jersey cows. Changes in the rumen fermentation and ruminal microbiome in Holstein cows may be associated with a better adaptation ability to heat stress. Our findings may inform future research to better understand how heat stress affects the physiology and productivity of dairy cattle breeding in southern China and the development of mitigation strategies.

Non-proteinogenic amino acids, such as L-citrulline and L-theanine, have garnered attention for their potential health benefits, including enhanced immunity, antioxidant activity, and cardiovascular support. The application of natural amino acids in disease treatment and health supplementation is and will remain a research hotspot in pharmaceutics. Plant-derived L-citrulline and L-theanine have demonstrated multifaceted benefits, primarily through mechanisms involving nitric oxide (NO) bioavailability (for L-citrulline) and mitochondrial regulation or immune modulation (for both). Critical gaps are identified: (1) the role of D-amino acids (e.g., D-citrulline and D-theanine) in health and metabolism remains underexplored, particularly regarding chiral-specific bioactivity; (2) derivatives and co-administration strategies of L-forms warrant systematic evaluation for drug. However, while these compounds show promise, evidence is predominantly from animal and cell studies, with limited long-term human data on efficacy and safety. Potential side effects, dosing limitations, and sourcing challenges are discussed. This review emphasizes the need for cautious interpretation of their benefits, acknowledging that while promising, some effects, such as those on muscle protein synthesis, require further validation compared to established nutrients like branched-chain amino acids. By bridging mechanistic insights with translational challenges, this work aims to guide future research toward sustainable nutraceutical production.