Betaine, chemically known as trimethylglycine or trimethylaminoetolactone, the molecular formula is C5H11NO2 and the relative molecular weight is 117.15.Amphoteric compound, neutral in aqueous solution, white ribate or leaf crystal, melting point 293℃, can withstand the high temperature of less than 200℃, with strong oxidation resistance, moisture retention.

Betaine metabolism can produce lysine, which provides the framework for the synthesis of carnitine. Meanwhile, it can provide active methyl as the synthetic raw material, which has the ability to increase the synthesis of carnitine. The active form of carnitine is long chain lipophthalic carnitine, namely acid-insoluble carnitine. The increase of methyl content in animals can promote the transformation of carnitine to acid-insoluble carnitine. Long chain fatty acids can be transported to mitochondria for β -oxidation by binding with carnitine to lipoacylcarnitine. The synthesis amount of free carnitine in liver increases, which enhances the transport of fatty acids, thus promoting fatty acid oxidation, and thereby enhancing the activity of lipolytic enzymes in different stages of pig and accelerating fat decomposition. It was found that betaine supplementation increased carnitine content in liver and longissimus dorsi muscle and the ratio of carnitine to lipoylcarnitine, reduced carcass fat and improved carcass quality.

Choline can be synthesized into phosphatidylcholine (PC) with the participation of diacylglycerol, which is an essential component of VLDL and other lipoproteins. During the transport process, choline and other carrier protein fat will be stored in the form of droplets in local tissues and organs. Betaine, as an efficient methyl donor, can save the consumption of choline in animals. The serine produced after betaine demethylation provides the framework for choline synthesis, and provides methyl for choline synthesis by increasing the content of active methyl donor. The addition of betaine in the high-energy low protein diet of laying hens can increase the mRNA expression of apoA1 and ApoB100 in liver and enhance lipid transport in liver, thus preventing fatty liver.