This episode of the Real Science Exchange podcast was recorded during a webinar from Balchem’s Real Science Lecture Series.
Choline was discovered in 1862 in pig and ox bile (“chole” in Greek). It is a simple nutrient containing five carbons and a nitrogen. Choline is considered a quasi-vitamin since its requirements and de novo synthesis are both higher than the B vitamins it’s similar to. Pigs can synthesize more choline than chickens. Choline is considered to be a conditionally essential nutrient depending on the physiological stage and choline production ability of the species being considered. (3:29)
Choline is involved in cellular maintenance and growth at all life stages. In particular, it’s involved in neurotransmission as a component of both sphingomyelin and acetylcholine. Phosphatidylcholine is a major component of cellular and organelle membranes and is involved in lipoprotein synthesis for the transport of lipids. Choline is converted to betaine upon oxidation, and betaine plays an important role in one-carbon metabolism as a methyl group donor. (8:43)
Dietary-free choline is preferentially used for acetylcholine and phosphatidylcholine synthesis. Phosphatidylcholine is the most abundant form of choline in the body. In general, water-soluble forms of choline are absorbed faster and have a higher tissue incorporation rate than lipid-soluble forms. (14:58)
Clinical signs of choline deficiency include reduced growth and reproductive performance. In pigs and chickens, choline-deficient diets lead to lipid accumulation in the liver. In broiler chickens, perosis is a classic choline deficiency sign and may progress to slipped tendons. From human studies, we know that insufficient methylation capacity during early development increases the risk of neural tube defects and impaired cognitive function. (16:44)
As animals age, their dietary source of choline transitions from water-soluble forms to lipid-soluble forms. Mammalian young receive water-soluble choline from milk, and avian species from the egg yolk. After weaning in pigs and at the hatch in chickens, the dietary choline source transitions to lipid-soluble forms found in oilseed meals. Dr. Dilger goes on to describe choline concentrations in common feedstuffs and supplements. Feedstuff type and processing methods have a profound influence on bioavailable choline content. (19:16)
Dr. Dilger details some of his work with choline and betaine in poultry diets. The requirement for preformed choline is relatively high for poultry because they lack capacity in a particular methyl transferase enzyme responsible for de novo synthesis. They also have relatively high choline oxidase activity which favors the formation of betaine from choline. Betaine is critical as a buffer to counteract the toxic effects of uric acid in the avian kidney. Dr. Dilger describes choline dietary requirements for avian species. (27:38)
Pigs have more efficient methyl transferase activity for de novo synthesis of choline. Sufficient choline is provided by milk and practical diets. For growing pigs consuming corn-soybean meal diets where methionine can completely spare choline, there is little benefit of choline supplementation for growth. Choline requirements increase for gestating and lactating sows. Swine requirements for choline were set in the 1940s and 1950s. Dr. Dilger believes these requirements need a second look given the great changes in pig and crop genetics since the requirements were originally established. To that end, work in his lab has shown that choline intake during gestation and lactation influences sow milk composition, body choline concentrations and forms, metabolomic profiles and brain development of pigs. (35:18)
In conclusion, Dr. Dilger considers choline a pervasive nutrient due to its crucial metabolic roles. Species-specific idiosyncrasies drive choline requirements, and analytical data for choline-related compounds is lacking. Different forms of choline have different metabolic kinetics and the potential for choline deficiency remains a practical issue. (46:15)
In closing, Dr. Dilger answers an extensive set of questions from the audience. Watch the full webinar at balchem.com/realscience. (48:32)
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