Oxidative Stress and Ultrastructural Changes in Laminar Tissue of Dairy Cows with Acute Laminitis Induced by Oligofructose Overload

This study explored ultrastructural changes and the expression of oxidative stress-related genes and proteins in the laminar tissue of dairy cows with acute laminitis induced by oligofructose (OF) overload. Twelve clinically healthy, non-pregnant Chinese Holstein cows were randomly allocated into two groups: the OF-overload group (n = 6) and the control group (n = 6). 17 g/kg BW of oligofructose (OF) dissolved in 20 mL/kg BW of deionized water was provided to the OF-treated group, while the control group received 20 mL/kg BW of deionized water via a stomach tube. Laminar tissue samples were collected at 72 h post-OF administration. RT-qPCR revealed significantly increased Keap1 mRNA expression (p = 0.0097) and significantly decreased Nrf2 (p < 0.0001), Ho1 (p < 0.0001), and Nqo1 (p = 0.0101) mRNA expression in the OF group compared to the control group. Western blot analysis confirmed corresponding protein-level changes, with significantly increased Keap1 (p = 0.0062) and significantly decreased Nrf2 (p = 0.0008), Ho1 (p = 0.0297), and Nqo1 (p = 0.0004) in the OF group compared with the control group. Immunohistochemical analysis revealed significantly increased cytoplasmic Keap1 distribution (p = 0.0200) and significantly decreased nuclear Nrf2 localization (p = 0.0032) in the OF group than the control group. Ultrastructural examination revealed significant pathological changes in the OF group, including a reduced number of hemidesmosomes (p < 0.01), an increased distance from epidermal basal cells to the lamina densa (p < 0.01), thickened and damaged lamina densa with disorganized collagen fibers, and deformed basal cell nuclei with reduced chromatin relative to the control group. In conclusion, these findings demonstrate that OF-induced acute laminitis is associated with significant dysregulation of the Keap1-Nrf2 antioxidant pathway and severe ultrastructural damage to the dermal–epidermal interface, suggesting that oxidative stress contributes to laminar tissue injury in dairy cows.