Vitamin K3 MNB (menadione nicotinamide bisulfite complex, CAS 1134-40-3) is the mainstream high-stability commercial form of feed-grade vitamin K3. It is produced from menadione and nicotinamide through a molecular complexation process. The mainstream market specification is MNB 96% (calculated as menadione active ingredient). It appears as a yellow to orange-yellow crystalline powder with low hygroscopicity, good flowability, and ready solubility in water. Through the hydrogen-bonding inclusion effect of nicotinamide, this form effectively shields the oxidation sensitivity of menadione. Compared with the traditional MSB (menadione sodium bisulfite) form, it exhibits significantly better chemical stability during high-temperature pelleting, high-humidity storage, and when combined with strongly oxidizing substances such as choline chloride and trace elements. It also generates less dust and provides higher mixing uniformity. It is widely used in aquafeed, pet food, starter feed for young animals, and compound premixes with stringent quality requirements, making it the preferred commercial form of vitamin K3 for feed companies seeking processing tolerance and shelf life.