The objective of this study was to explore the relationship between calf birth traits and their susceptibility to diseases before reaching adulthood. A total of 5253 birth traits of Chinese Holstein calves were examined, including gestation length (GL), calf weight at birth (CW), and calving ease score (CES), which ranges from 1 (easy) to 5 (very difficult). Furthermore, monthly medical records were scrutinized for pneumonia and diarrhea in these calves. The study assessed five aspects of disease manifestation in calves: age at first onset, frequency of illness, longest duration of treatment, and total duration of treatment. The link between age at onset and disease manifestation prior to adulthood was analyzed using general linear models and regression models. The GL of calves significantly correlated with the risk of pneumonia, with the risk decreasing as the GL increases. A higher CES was associated with a later onset of diarrhea in calves. Furthermore, the CES was significantly negatively correlated with the duration of diarrhea treatment in calves. These results suggest that implementing different preventive measures for calves with different birth traits and modifying treatment protocols for affected calves could enhance the productivity of dairy cows and reduce losses on farms.

Global warming exacerbates heat stress in dairy cows, while traditional indicators like the Temperature-Humidity Index (THI) struggle to accurately reflect individual physiological response variations. This review systematically analyzes the dynamic changes in the bovine immune system under heat stress and proposes immune-related biomarkers as a novel strategy for early warning and individualized assessment. Research reveals that heat stress compromises the innate immune barrier function of cows, suppressing neutrophil chemotaxis and antimicrobial peptide synthesis, leading to a decline in the opsonophagocytic index and endotoxin translocation. Expression of intestinal tight junction proteins (e.g., Claudin-1, Occludin) is significantly downregulated (by ~40%), causing endotoxin translocation (serum LPS increases ~3-fold) and disruption of the blood-milk barrier, increasing mastitis risk by 2–3 times. Regarding adaptive immunity, the proliferation and differentiation of T/B cells are impaired, the CD4+/CD8+ T cell ratio decreases, antibody affinity maturation is suppressed, and the efficiency of immune memory formation post-vaccination is reduced. Concerning mammary immunity, the number of viable granulocytes in milk decreases, mammary epithelial cells increase, pro-inflammatory cytokine levels rise, and the risk of clinical mastitis increases 2–3 fold. Furthermore, heat stress induces metabolic reprogramming, gut microbiota dysbiosis, oxidative stress, and activation of the hypothalamic-pituitary-adrenal (HPA) axis. Novel biomarkers, such as Heat Shock Proteins (HSPs), Neutrophil-to-Lymphocyte Ratio (NLR), cytokine profiles (e.g., IL-6/TNF-α), acute-phase proteins (e.g., Haptoglobin, Hp), and epigenetic markers, provide crucial targets for heat-tolerant breeding and early intervention, promising to enhance the climate resilience of the dairy industry.

Introduction: Subclinical mastitis in dairy cows is an asymptomatic inflammatory condition of the mammary gland during lactation. It is frequently associated with reduced milk yield, impaired milk quality, and an elevated risk of progression to clinical mastitis. The dysregulation of immune homeostasis characterizing this subclinical state represents a significant yet often overlooked concern in dairy herds.Methods: We characterized T cell subsets in cows with Staphylococcus chromogenes-induced subclinical mastitis and healthy controls.Results: We found that S. chromogenes infection induced an increase in the percentage of γδ T cells and a decrease in CD4⁺CD8⁺ double-positive (DP) T cells within milk cells, while significantly elevating the percentage of γδ T cells expressing CD44. Cell sorting combined with quantitative RT-PCR has indicated that infection by S. chromogenes may activate γδ T cells. Specifically, in subclinical mastitis milk, the expression levels of five cytokines—IFN-γ, IL-2, TNF-α, IL-17, and GZMB—were significantly higher in WC1⁺ γδ T cells compared to healthy cows. Furthermore, these cells released elevated levels of PRF1, which directly killed target cells infected with bacteria compared to the levels observed in healthy cows.Discussion: Our results reveal, for the first time, the significant role of γδ T cells in S. chromogenes -induced subclinical mastitis, providing new insights into the immune protective mechanisms against subclinical mastitis in cows.

Bovine foot rot, an infectious disease caused by Fusobacterium necrophorum , leads to significant economic losses in the dairy farming. Research on bovine foot rot has primarily focused on the isolation and identification of the pathogen, as well as treatment methods. However, few studies have reported on the host’s immunological characteristics following infection. In this study, we employed an eight-color flow cytometry panel to characterize T-cell immune responses in dairy cows after infection by the F. necrophorum naturally-induced foot rot. We found that dairy cows with natural F. necrophorum-induced foot rot exhibited significantly increased percentages of NK cells, NKT cells, CD4 ⁺ CD8 ^- (helper) T cells, and CD4 ⁺ CD8 ⁺ (double-positive) T cells compared to healthy cattle, while the proportion of WC1 ⁺ γδ T cells remained unchanged. However, the frequency of CD44 ^High expressing cells was significantly elevated across all these T-cell subsets, suggesting their differential activation upon host infection with F. necrophorum . Compared with healthy cows, those with natural F. necrophorum -induced foot rot showed a significant increase in the percentages of effector memory T cells within NK and CD4 ⁺ CD8 ⁺ T cell populations, and of central memory T cells within CD4 ⁺ CD8 ⁺ and CD4 ⁺ CD8 ^- T cells, respectively. Our results, for the first time, revealed a potential role of CD4 ⁺ CD8 ⁺ T cells and NK cells in the defense of F. necrophorum naturally-induced foot rot in cows.