Introduction: Calves in the lactation period exhibit limited disease resistance and stress tolerance, making them particularly vulnerable to health challenges such as diarrhoea. Yeast culture (YC) supplementation has emerged as a promising strategy to enhance health and growth in young ruminants. This study aimed to investigate the effects of YC supplementation on growth performance, antioxidant capacity, immune function, and intestinal microbiota composition in lactating Holstein calves.Methods: A total of 40 lactating Holstein calves were randomly assigned to either a control group or a YC-supplemented group, with the feeding trial lasting 60 days. Growth performance parameters were recorded, serum antioxidant and immune markers were evaluated, and gut microbial diversity and composition were analysed using metagenomic sequencing. Furthermore, correlations between microbial taxa and serum markers were assessed.Results: The results showed that YC supplementation significantly increased average daily gain (ADG) and feed intake, and reduced the incidence of diarrhoea (p < 0.05). Serum levels of total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD), and glutathione peroxidase (GSH-Px) were significantly elevated, while malondialdehyde (MDA) content was significantly decreased (p < 0.05), indicating improved antioxidant status. Immunoglobulin and cytokine levels were also significantly higher in the YC group (p < 0.05). Metagenomic analysis revealed a significant increase in the Chao index and a trend toward higher Shannon diversity in the YC group. YC supplementation notably increased the relative abundance of beneficial bacteria such as Phocaeicola plebeius, Ruminococcus sp., Segatella copri, and Candidatus Scatovivens faecipullorum, while reducing potentially pathogenic bacteria like Candidatus Cryptobacteroides sp. and Dorea sp. Correlation analysis showed that T-AOC was positively associated with P. plebeius and S. copri, while MDA was positively correlated with Candidatus Cryptobacteroides sp. and negatively correlated with Ruminococcus sp. and other beneficial taxa. Similarly, several immune markers exhibited positive correlations with beneficial bacteria and negative correlations with harmful bacteria. Functional pathway analysis suggests that YC may enhance immune responses and antioxidant capacity through activation of the T cell receptor and B cell receptor signalling pathways.Discussion: In conclusion, YC supplementation improved growth performance, enhanced antioxidant and immune functions, and favourably modulated gut microbiota in lactating Holstein calves. These changes collectively contributed to reduced diarrhoea incidence and improved overall health, highlighting yeast culture as a valuable nutritional strategy for calf health management.

Calf diarrhea is a common early-life disorder that adversely affects growth, oxidative balance, immune function, and intestinal microbiota, thereby compromising health and production performance. This study systematically investigates the effects of naturally occurring diarrhea in 7-day-old suckling calves on oxidative stress, immune responses, intestinal barrier integrity, and gut microbiota structure and function. Fecal scores, serum antioxidant and immune indices, and intestinal permeability markers were measured, and fecal samples were subjected to metagenomic sequencing. Diarrhea-affected calves exhibited higher fecal scores, increased oxidative stress indicated by reduced total antioxidant capacity, elevated lipid peroxidation, and altered antioxidant enzyme activities. Humoral immunity was impaired, inflammatory responses were dysregulated, and intestinal barrier function was disrupted. Gut microbial diversity declined, showing a depletion in health-associated taxa and the enrichment of opportunistic pathogens. Correlation analyses revealed that pathogenic bacteria abundance positively associated with diarrhea severity, oxidative stress, inflammation, and barrier disruption, while beneficial genera correlated with antioxidant and immune function. Functional profiling indicated a microbial shift from amino acid metabolism and antioxidant homeostasis toward carbohydrate and energy metabolism under diarrheic conditions. These findings highlight the pivotal role of gut microbiota dysbiosis in diarrhea pathogenesis and provide a foundation for developing microbiome-targeted interventions to improve calf health.

Background: Feline pulmonary Langerhans cells histiocytosis (PLCH) is a rare disorder that results in progressive respiratory failure secondary to pulmonary parenchymal infiltration with Langerhans cells (LCs). A diagnosis of PLCH is proposed based on the clinical features and pathological findings and confirmed based on the infiltrating histiocytic cells. There are few documented cases of feline PLCH, and this case report of PLCH in an African Lion could present new information and aspects of this feline histiocytic disease. Case presentation: An African lion at Hohhot Zoo showing severe hyporexia and dyspnea with subsequent mental depression and emaciation died of exhaustion after a 35-day course of illness. Empirical treatment did not have a significant effect. An autopsy revealed that the lungs were enlarged and hardened due to infiltrative lesions, with many yellowish-white foci in all the lobes and sections. Furthermore, the kidneys were atrophied and had scattered grayish-white lesions on the surface. At the same time, congestion was widely distributed in various locations, including the liver, subcutaneous loose connective tissues, serosal surface and other tissues and organs. Histologically, proliferative histiocytic cells (PHCs) were scattered in the alveolar cavities, bronchioles and submucosa of bronchioles, with evident cellular and nuclear pleomorphism, and thus the alveolar septa were obliterated. The histopathological changes in other organs included chronic sclerosing glomerulonephritis, proliferated Kupffer cells in the liver, adrenal edema and interstitial connective tissue hyperplasia, as well as atrophy of the small intestines and spleen. Furthermore, immunohistochemical analysis results were strongly positive for CD1a, vimentin, S100 and E-cadherin in the membrane or cytoplasm of PHCs, supporting an LC phenotype. Conclusions: Here, we present a rare pulmonary Langerhans cell histiocytosis case in an African lion.

Compound yeast culture (CYC) is known to enhance animal health, but its effects on hepatic immune function are unclear. This study systematically examined CYC’s regulatory effects on the liver of weaned lambs using transcriptomics and integrative bioinformatics. Ten lambs were randomly assigned to a control diet or a basal diet supplemented with 30 g/d per head of Saccharomyces cerevisiae and Kluyveromyces marxianus co-culture (CYC group) for 42 days. Histological analysis showed that CYC improved hepatocyte arrangement and sinusoidal integrity, suggesting enhanced hepatic tissue stability. Cytokine analysis revealed CYC significantly increased IL-6 and IL-1β while reducing IL-10, TGF-β1, TNF-α, and CXCL9, indicating a bidirectional modulation of the immune response. Additionally, CYC enhanced antioxidant defenses by increasing T-SOD, GSH-Px, and T-AOC activities and decreasing MDA content. Transcriptomic sequencing indicated that CYC reshaped hepatic gene expression. Upregulated genes were enriched in immune-regulatory and structural pathways, including PI3K-AKT signaling, ECM–receptor interactions, Toll-like receptor pathways, and cell adhesion molecules. Protein-level validation further confirmed activation of PI3K and AKTAKT phosphorylation with limited engagement of NF-κB signaling. Conversely, downregulated genes were mainly associated with oxidative stress and energy metabolism, such as ROS-related pathways and MAPK signaling. WGCNA identified key hub genes (PTPRC, CD86, and ITGAV), which correlate with pro-inflammatory factors and participate in immune recognition, T-cell activation, and cell adhesion. These data suggest that CYC promotes hepatic immune homeostasis by enhancing immune signaling, stabilizing tissue architecture, and modulating oxidative stress/metabolic processes. This study provides mechanistic insights into CYC’s regulation of liver immune function and supports its targeted application as a functional feed additive for ruminants.