Magnesium oxide is the most commonly used inorganic magnesium source in animal feed. Its core function is to provide the macronutrient mineral element magnesium, which participates in the activation of over 300 enzymes in the body, energy metabolism, neuromuscular conduction, and bone mineralization. In breeding, it is particularly important for ruminants, as it can effectively prevent hypomagnegic spasm (grass spasm), and at the same time help perinatal dairy cows prevent postpartum hypocalcemia by regulating the difference of cations and anions in the diet. In monogastric animals, magnesium oxide is used to maintain bone health and electrolyte balance, and to assist in the normal functions of nerves and muscles. It should be noted that the bioavailability of magnesium in magnesium oxide is relatively low. However, due to its high magnesium content and low cost, it remains the most mainstream choice in complete compound feed. When adding it, the dosage should be precisely controlled based on the animal species, growth stage and dietary calcium and phosphorus levels. Excessive use may cause diarrhea or interfere with the absorption of other mineral elements.