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Background: Sphingolipids (SL) are key regulators of inflammatory processes, yet their roles in dairy cows remain poorly understood. This study investigated the effects of inflammation (plasma haptoglobin concentration), ketosis, and mastitis on plasma SL profiles in Holstein cows sampled seven days postpartum. From a cohort of 427 cows across 25 farms, 80 animals were classified into four groups: inflammation (n = 20), ketosis (n = 19), mastitis (n = 21), and healthy controls (n = 20). Plasma SL were quantified by targeted HPLC-MS/MS, while cytokines were quantified with a 15-plex bead-based assay. Both univariate and multivariate analyses were applied to assess pathological effects, along with SL ratios and correlations between SL and cytokines.

Results: Systemic inflammation detected through the haptoglobin measure induced the most pronounced alterations in SL metabolism, characterized by elevated dihydrosphingomyelins (DHSM) and lactosylceramides (LacCer), higher C22-24:C16 ratios, and lower unsaturated:saturated ratios in ceramides (Cer) and sphingomyelins (SM). Although total Cer, SM, and the Cer:SM ratio remained unchanged, specific reductions were observed in both Cer and SM in C14, Cer C18:1, SM C16:1, and SM C23:1, whereas SM C25:0 and C26:0 increased. Sphingosine-1-phosphate (So1P) was positively correlated with IL-10 as well as IL-1α and TNFα, while C18-20 Cer correlated positively with multiple pro-inflammatory cytokines and chemokines such as CXCL8 and CCL2. Ketosis induced subtler changes, primarily an increase in plasma DHSM and DHSM:SM ratio (driven by C16:0), an increase in C22-24:C16 DHCer ratio, and a decrease in both LacSo:LacCer and unsaturated:saturated ratios in C23-SM. In this group, So1P correlated positively with CXCL8 and CCL2. Moreover C18-20 Cer and DHCer were positively associated with CXCL8, CCL2, CCL3, and CCL4, which also showed correlations with most LacCer species. Analysis of chronic mastitis cases yielded a clear separation from controls in multivariate analysis but only minimal changes in SL concentrations and ratios, maybe due to the localized nature of the inflammatory response.

Conclusions: In summary, heightened inflammatory response in early post-partum is associated with the strongest systemic effects on SL metabolism, followed by ketosis, while mastitis induced only modest alterations. These findings highlight condition-specific patterns of SL regulation postpartum and suggest potential immunometabolic biomarkers of disease.

Background: Selective breeding for disease resistance is an effective strategy to control duck hepatitis A virus type 3 (DHAV-3) in waterfowl. However, the mechanism underlying resistance remains poorly understood, particularly those associated with antioxidant defense, intestinal development and host-microbiota interactions.

Method: A total of 100 1-day-old Pekin ducklings were used in this study with 50 DHAV-3 susceptible and resistant ducks, respectively. Samples were collected at 7 days post-hatching (D7), D21 and D42, 10 birds per group. We compared DHAV-3 resistant and susceptible ducks during early development with respect to immune organ indices, antioxidant capacity, intestinal morphology, barrier-related gene expression and cecal microbiota.

Result: Resistant ducks exhibited higher spleen indices and stronger antioxidant capacity, characterized by increased superoxide dismutase, reduced glutathione, and total antioxidant capacity, along with lower malondialdehyde levels at D7 and D21. In contrast, susceptible ducks showed compensatory thymus hypertrophy and delayed development of antioxidant defense and intestinal maturation. Ileal morphology revealed greater villus height and width with more regular arrangement in resistant ducks at D7, whereas these differences diminished at D21 and D42. Gene expression analysis demonstrated higher early expression of the tight junction proteins CLDN1 and CLDN3 in resistant ducks, while susceptible ducks displayed elevated MUC2 and OCLN, suggesting stress induced compensatory responses. Cecal microbiota analysis revealed distinct colonization patterns in early development. Resistant ducks were enriched with Firmicutes and beneficial genera such as Enterococcus and Lactobacillus, whereas susceptible ducks harbored higher abundances of Bacteroidota and potentially opportunistic taxa. Microbial diversity increased with age in both groups, but resistant ducks displayed more orderly succession and enrichment of SCFA producing genera, including Subdoligranulum and Phascolarctobacterium, which positively correlated with plasma antioxidant indices.

Conclusion: DHAV-3 resistant ducks exhibit early advantages in antioxidant defense, intestinal barrier development and colonization by beneficial microbiota, which collectively contribute to enhanced disease resistance. These findings highlight the synergistic roles of host physiology and gut microbiota in shaping resistance. In the future, integrating genomic selection with microbiota modulation and antioxidant interventions may accelerate the breeding of highly resistant duck lines and provide scientific evidence and practical strategies for controlling duck viral hepatitis.