Betaine, also known as glycine trimethyl inner salt, is a non-toxic and harmless compound. The appearance is white crystalline powder or granule, molecular formula is C5H12NO2 and molecular weight is 118, and melting point is 293°C. It has light sweet taste and is a substance similar to vitamins. Currently widely used in feed breeding industry, betaine is used as a feed additive to increase pig body weight and improve feed conversion efficiency.

Betaine is a buffer against osmotic shock. When the osmotic pressure outside the cell changes dramatically, the cell can absorb betaine from the outside to maintain the normal osmotic pressure balance, and prevent the diversion of water in the cell and the invasion of salts. At the same time, betaine can improve the function of potassium and sodium pump of cell membrane, which can ensure the normal function and nutrient absorption of intestinal mucosal cells. The buffering effect of betaine on osmotic shock plays an important role in maintaining normal physiological functions under stress conditions such as diarrhea of piglets, water change and molting of aquatic animals.

Betaine can stimulate the sense of smell and taste of animals, and it is a good attractant, especially for aquatic animals. It has the functions of increasing food intake and survival rate, reducing feed coefficient, and promoting growth. Scholars from Kagoshima University in Japan measured the point response of carp trigeminal nerve, mandibular page and limb bones to amino acids and betaine. The results showed that betaine has independent taste perception and can enhance the taste perception response of other amino acids. The chemical structure of betaine is suitable for the smell and taste receptors of fish.