Betaine is a natural compound found in variable concentrations in most living organisms, including plants and animals. Wheat and sugar beets are two common ingredients with a high concentration of betaine. Pure betaine is considered safe (it belongs to the GRAS group) when used within approved limits. Addition of pure betaine in pig and poultry diets is practiced with increasing frequency because betaine has certain functional properties that make it a conditionally essential nutrient (or additive). However, in order to obtain optimum results from betaine, it is important to know what level of betaine is best to use.
Pure betaine is extracted from beets
Betaine for commercial use is extracted from sugar-beet molasses. Although sugar beets contain much less betaine than wheat (about 80 percent less), molasses is a much easier ingredient for the extraction process, which involves chromatagraphic separation and crystallization. Less frequently, betaine may be extracted from vinasse, a by-product of sugar beet ethanol production.
Commercial forms of betaine include anhydrous betaine, betaine monohydrate, betaine monohydrochloride (25 percent hydrochloride), and betaine monophosphate salt. No specific form has been shown to offer any substantial benefits over the others, assuming the reduced pure betaine concentration is taken into account in the non-anhydrous products.
The story of betaine
There are many betaines, and they are all characterized as a zwitterion; a chemical compound that has both a positive and a negative charge on different atoms, but on balance it is neutral. The first such compound was discovered in sugar beets (hence the name, betaine) in the 19th century, and its proper chemical name today is trimethylglycine, although it is also known as glycine betaine. Other betaines have not been studied in animal nutrition, and thus, only beet-derived betaine is considered in this discussion.
Because betaine is a methyl derivative of the amino acid glycine, it contains three chemically reactive methyl groups (CH3). This property gives betaine one of its two biological functional roles, that of a methyl donor. The second role is that of a natural organic osmolyte involved in the regulation of water osmosis that maintains water equilibrium across all biological membranes.
Betaine inside the organism
Animals are capable of synthesizing betaine to cover their needs, under most conditions. Betaine synthesis is by oxidation of the well-known vitamin choline. Supplying pure betaine in the diet has been shown to spare the more expensive choline, which is also being added in the diets of pigs and poultry. As a methyl donor, betaine can also replace methionine, an expensive amino acid. As such, dietary betaine supplementation can reduce the need for methionine and choline fortification, assuming of course, prices are favorable for such sparing effect to be of any practical importance under commercial conditions. Betaine can also act as a lipotropic agent, reducing, in some studies, carcass fat deposition in growing pigs by as much as 15 percent when used at only 0.125 percent in feed.
Finally, betaine has been shown to improve nutrient digestibility due to the osmotic protection it offers to intestinal bacteria that enables them to develop more stable gastrointestinal conditions. Naturally, the most important role of betaine is that of preventing cellular dehydration, but quite often this role is taken for granted, and as such it is overlooked.
Betaine against dehydration
Excess dietary betaine, not utilized as a methyl donor, can be used to regulate cell hydration during times of water scarcity. During heat stress, cells respond by gathering inorganic ions, such as sodium, potassium, and chloride, and organic osmolytes such as betaine. In this role, betaine is the most efficient compound, because it does not have the negative aspects of inorganic ions in destabilizing proteins. As an osmolyte, during water stress conditions, betaine can protect the kidneys from high concentrations of electrolytes and urea, improve the function of macrophages, regulate water balance in the gut, and prevent premature cellular death, with implications in embryonic survival.
From a practical point of view, it has been reported that betaine supplementation can sustain gut health in weaned pigs, by preventing villus atrophy and supporting the activity of proteolytic enzymes. In a similar function, birds suffering from coccidiosis showed signs of improved gut health when their diet contained supplemental betaine.
Based on experimental and empirical evidence, it can be argued that dietary supplementation with pure betaine can slightly improve nutrient digestibility and lead to enhanced growth and feed conversion in broilers, turkeys, and ducks. In addition, betaine in poultry diets may lead to less carcass fat and more breast meat. Of course, the exact magnitude of such effects can be very variable. In addition, under practical conditions, it can be accepted that the relative bioavailability of betaine compared to methionine is 60 percent, or in other words, it can be said that 1 kg anhydrous betaine can replace 0.6 kg of added methionine. In regards to choline, it has been estimated that on average betaine can replace about 50 percent of added choline in broilers, and 100 percent in laying hens.
Nevertheless, following a more conservative approach that allows for the fact that choline has further biological roles, it is recommended to replace no more than 25 percent of added choline with pure betaine. A meta-analysis of the effects of dietary betaine supplementation on pig performance and carcass characteristics, including 19 studies, indicated that betaine did not significantly affect growth rate, but it did improve significantly feed efficiency (2-8 percent) and carcass yield, while reducing backfat deposition (10-20 percent). The methionine and choline sparing effect of betaine in pigs is not well documented and as such it is not considered of practical significance at the moment.
There is no doubt that betaine can offer substantial benefits to animals stressed by the lack of water, which will benefit the most from betaine. These include (1) heat-stressed animals, especially broilers during the summer months, (2) lactating sows that almost always consume less water than they need, and (3) all animals drinking saline water.
It is best to limit betaine inclusion rate to no more than 1 kg per metric ton of complete feed, in all species that have been identified as being able to benefit from betaine supplementation. At inclusion levels that exceed this recommendation, betaine efficiency appears to diminish as the dose increases. Nevertheless, under specific cases, betaine inclusion rate may be increased up to 2 kg per metric ton for a short period of time. This can be the case of extreme heat stress, or in very young animals that do not consume enough feed and water, or when prices for Methionine or choline are extremely high.