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 will affect the digestion and utilization of nutrients. Studies in pigs and poultry have found that betaine can improve the digestibility of dry matter or organic matter in the ileum or total digestive tract. Increasing the level of betaine in broiler diets from 0.05% to 0.10% can improve the digestibility of crude protein and significantly increase the digestibility of crude fiber. Studies on piglets have found that betaine can increase the ileal digestibility of amino acids and increase the digestibility of neutral detergent fiber and acid detergent fiber in the ileum and total digestive tract. Since the intestinal cells of pigs and poultry do not produce fiber degrading enzymes, the increase in the digestive capacity of the digestive tract fiber indicates that betaine may stimulate the fermentation of fiber by intestinal microbes.

Osmotic adjustment refers to maintaining the structure and function of cells by regulating the inflow and outflow of water. As an osmotic regulator, betaine plays an important role in maintaining the morphology and function of intestinal cells. Changes in the water content of cells will affect the ionic strength, which in turn affects the structure of intracellular enzymes and proteins. Betaine accumulates in the organelles of cells subjected to osmotic pressure and ionic pressure to replace inorganic ions, thereby protecting the enzymes and cell membranes in cells from damage by inorganic ions.

Betaine can also increase the volume of cells and the content of free water in cells under high osmotic pressure, thereby maintaining the normal proliferation ability of cells. Since the absorption of nutrients depends on the intact intestinal epithelium, the osmotic adjustment effect of betaine may also improve the digestion of nutrients. Similar to intestinal cells, intestinal microorganisms are also exposed to various osmotic conditions. Betaine plays an osmotic regulation effect in many Gram-negative bacteria and Gram-positive bacteria, helping microorganisms resist osmotic stress.