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.

Pigs eating betaine can improve the quality of pork. Betaine is mainly used as a high-efficiency methyl donor to accelerate the β-oxidation of animal cells and the transcription of certain protein genes, thereby reducing animal body fat and increasing protein deposition. Betaine can promote the growth of pigs and improve carcass quality. Betaine inhibits the key enzymes of fat synthesis to reduce fat synthesis and relatively fat deposition. At the same time, by increasing the content of carnitine, it accelerates the β-oxidation of fat and enhances the decomposition of fat.

The oxidation of long-chain fatty acids in the body is carried out in the cell mitochondria, while long-chain fatty acids and ester acyl-coA are difficult to pass through the inner mitochondrial membrane, and the carrier carnitine must be involved. Betaine can increase the synthesis of carnitine in the liver, enhance the carrying of fatty acids, promote the β-oxidation of fatty acids in the mitochondria of fat and muscle cells, and thereby feedback the activity of lipolytic enzymes in different stages of pigs. In order to break down fat, the fat deposits in the body are relatively reduced. Betaine significantly reduces the activity of malate dehydrogenase (MDH), but has no significant effect on glucose-6-phosphate deaminase (G-6-P) and isocitrate deaminase (ICD), that means it has effect of stabilize MDH, so that its activity will not be greatly changed due to lipolysis. For piglets, because the content of these three enzymes in the subcutaneous fat tissue is small, betaine has a tendency to reduce its activity, but the effect is not significant. Therefore, betaine reduces body fat mainly through the way of enhancing lipolysis to reduce carcass fat.