Choline is a small-molecular organic compound being essential to maintain the normal biological functions of animals and poultries; it is also the component of some important bio-active substances such as lecithin and acetyl Choline. Chloride, being

paid more and more attention, is widely used as feed additive in Choline chloride form.

1, The role of Choline in the organic metabolism and the growth of animals and poultries, as well as the relationships among Choline, methionine, and betaine.

Choline is a strong-base quaternary ammonium hydroxide, and choline chloride is the hydrochloride of Choline, whose water solution shows weak-acid.

Choline has four functions in the organic metabolism and the growth of animals and poultries as follows:
① It can be transferred into betaine and provides unsteady methyl or formed methionine combined with homocysteine;
② As an important component of lecithin, Choline plays an important role in the prevention of tibial dyschondroplasia of poultries and limb expansion of pigs;
③ Choline can promote fat transport in lecithin form or prevent abnormal fat accumulation by improving fatty acids utilization rate of the livers, thus it plays a key role in liver fat metabolism;
④ Participating in neural conduction. Choline is the precursor of a neurotransmitter named acetyl Choline and an important component of serums sphingomyelin. Choline chloride has significant effectiveness on promotion the growth and development of animals and poultries, improvement of meat and eggs qualities, and reduction of feedstuff consumption.
Methionine is an essential amino acid, and betaine is also called Tri-methyl ammonioacetate is an effective methyl donator.
The relations among Choline, methionine, and betaine are as follows:
① All of them can provide unsteady methyl playing an important role in many metabolisms;
②Betaine is the intermediate of Choline being a methyl donator．Betaine inverted from Choline transfers methyl to homocysteine to synthesize methionine;
③ Choline and betaine can not replace of methionine to use in protein synthesis. However, in dietary feedstuff seriously lack of Choline, betaine may protect methionine from being used as methyl donator, and the savage of methionine will promote growth.

2, Research on the application of choline chloride in feed additives
2.1 Evaluation of choline chloride availability
Research shows that the rate of biological utilization of Choline in feedstuff materials is fairly low; therefore, Choline is generally added to dietary feedstuff in choline chloride form. For the relative low prices of choline chloride and betaine, they can be added to the dietary feedstuff of broilers to replace of part methionine to reduce the cost, this has obtained good effects on the aspects of production performance and economical efficiency.

Betaine, the methyl donator intermediate of Choline, has been used widely in aquaculture industry as a nutrient additive and food attractant. Research showed that betaine could significant promotion of the growth of common carps (Cyprinus carpio), reduction of the liver steatosis of grass carps (Ctenopharyngodon idellus), and significant food-attracting response, thus it can shorten intake time and improve feedstuff transferring rate.

Choline firstly has been separated from pig bile at the end of 1940s and has been proved its good prevention effect in limb expansion of pigs.

2.2 Research on the choline chloride carriers and anti-moisture adsorption & anti-caking & methods
In feedstuff industry, Choline is directly added in choline chloride water-soluble solution form or absorbed in carriers to feedstuff. For choline chloride is the hydrochloride of Choline, whose molecular has polarity, thus it is extremely easy to absorb moisture, this bring somewhat difficulties to production, processing, storage, and feeding. Generally, choline chloride is mainly available in dust produced by even-absorbing choline chloride water solution in a certain carrier and drying. Therefore, the choice of carriers has important effect on anti-moisture and anti-caking in the production. The carriers of choline chloride have various species mainly silicon dioxide and botanical materials. They can be roughly divided into three types: agro-byproducts, natural minerals, and artificial synthetic compounds. Agro-byproducts mainly include wheat bran, corn grits powder, corn stalk powder, rice husk powder, peanut hull powder, starchy residue of tuberous species, etc. Natural minerals mainly include boiling stone, bentonite, sepioiite, and expanded pearlite, etc. Artificial synthesis material is mainly hydrazine silicic acid. To solve the moisture absorption & blocking problems of choline chloride, relative researches have been conducted on carrier choice and anti-caking agents’ addition. The general requirements of carrier choice are as follows:
① The carrier surface should be rough, suitable for the package of choline chloride and reduction of contact with external;
② They should have moderate mesh size (generally in the range of 60-80 meshes) and apparent density (generally in the range of 0.3～0.5 g/mL) to avoid uneven blending and graded sediment in use, suitable for package;
③ They should contain fairly low water content, and they own are not easy to absorb moisture and block;
④ Stable chemical property and moderate acid-base degree. The anti-caking agent of choline chloride has been developed successfully, for example, glycerol triacetate can form a moisture-absorbing layer in choline chloride surface to block the contact of choline chloride with moisten air.