MAPK8 and magnesium deficiency: In our current study, apart from systematic research on the relationship between magnesium deficiency and TJs, we innovatively investigated the relationship between magnesium deficiency and oxidation, antioxidants, and cell apoptosis as well as the corresponding signalling molecules (Nrf2, MLCK and JNK) in animal intestines, aiming to determine the possible mechanism of fish intestinal structural integrity with magnesium treatment.