Why is choline overlooked in monogastric nutrition?

Why is choline overlooked in monogastric nutrition?

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This simple compound is essential for the diet but may not be considered enough

Choline is “the most overlooked nutrient in monogastric nutrition,” according to Ryan Dilger, PhD., of the department of animal sciences at the University of Illinois-Urbana Champaign. He spoke February 23 as part of the Balchem Real Science Lecture Series.

Available in water-soluble and lipid-soluble forms, choline is important for all life stages of birds and mammals for several functions, including neurotransmission, membrane synthesis and lipid transport.

“These three are going to be the top priorities metabolically for the use of choline in the body,” Dilger said. “In general, they’re all relating to overall cellular maintenance and growth across the life stages.”

Choline also has the ability to donate a methyl group to become betaine, which can be used in a variety of roles.

“Owing to the fact that we have both betaine and folate serving as methyl donators here, we know when we have redundancy in the metabolic pathway how critically important that is going to be,” he said.

Water-soluble forms of choline are absorbed faster and elicit a higher concentration or incorporation rate of choline-containing compounds within the body compared with lipid-soluble forms.

Importance of choline in the diet

Dilger said choline deficiency in pigs and chickens leads to clear reductions in growth and reproductive performance, most likely related to accumulation of lipid within the liver.

Choline is important for reproductive function because of the importance of neurodevelopment early on. Dilger said choline deficiency is best defined as perosis in chickens, which causes the inability of the bird to properly form the cartilage within the joint, leading to leg problems – especially in broilers – with slipped tendons.

“Perhaps more overtly from a clinical sign perspective, we know tissue development abnormalities are going to occur with choline deficiency, and mainly being with bone and cartilage formation,” he said.

Dilger added that choline deficiency can manifest quickly, especially in chickens.

“Between lipid accumulation of the liver and perosis in the broiler chicken, these would be the most overt signs that we can point to,” he said.

Poultry have relatively high dietary requirement – higher than pigs. According to the 1994 Nutrient Requirements of Poultry, required choline for broilers is 750‐1,300 mg/kg diet; for laying hens, 1,100‐1,310 mg/kg diet; and for turkeys, 800‐1,600 mg/kg diet.

What are good choline sources?

Dilger said animals generally start out getting choline from water-soluble forms, such as mammals consuming water-soluble forms in milk or avian species through the egg yolk, and then they transition later in life to lipid-soluble forms.

“All of those species, and including humans, are going to transition on to foods that have more of it in the lipid-soluble form,” he said. “In our agricultural species, especially referring to oilseed meals.”

The main source of choline in feedstuffs is corn-soy-based diets. However, the bioavailability of choline will differ depending on the diet.

“Both the ingredient type and the form of choline that’s present are going to be important,” he said, so “it’s important when formulating this to make sure we are meeting the choline requirements,” adding that it is also important to include some form of choline supplement.

Choline requirements for pigs

Pigs have a lower choline requirement compared with chickens, and they can obtain sufficient amounts through milk and practical diets, Dilger said.

According to the 2012 Nutrient Requirements of Swine, choline requirements for starter/grower/finisher pigs are 400‐600 mg/kg diet; and for gestation/lactation are 600‐1,250 mg/kg diet.

Dilger said there is some evidence that higher choline intake may benefit reproductive performance of sows, with increased conception rate and increased total born alive.

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Gene Pesti says:

I have some answers to your question of why choline is overlooked in monogastric nutrition, at least for growing broilers. The main reason is that a clinical choline deficiency per se is difficult to demonstrate with practical diets. There appears to be enough choline present in corn and soybean meal-based diets to prevent perosis. The root problem is in the way requirements are determined. If methionine requirements are determined with an excess of all other nutrients, the methionine requirement will be low. If choline requirements are determined with an excess of all other nutrients, the choline requirement will be low. If broilers are fed the low “requirements” of methionine and choline they will fail to grow maximally. They will be deficient in labile methyl groups that can come from methionine, choline, betaine or dimethyl-thetin (as far as we know). Vitamin B12 and folate (the carriers of labile methyl groups) should have their requirements determined first and be fed in excess since their quantitative needs and costs are very low. Then the most economical source of methyl groups should be chosen. Studies of methionine and choline requirements are rarely conducted this way. And then there is the added complication that if excess protein is fed, it will increase the labile methyl needs for nitrogen excretion through uric acid synthesis in birds. In short, there is not enough information on just how to supplement methionine and choline or betaine to economize broiler growth.

Then there is the practical problem that the amounts and bio-availabilities of choline and betaine in feedstuffs are practically unknown. We demonstrated some time ago that the standard extraction method that was developed for choline assays with soybean meal does not get nearly all the choline that is in corn and other ingredients. Another complication is that many feed ingredients contain considerable amounts of betaine that is almost always ignored. While corn and soybean meal are practically devoid of any betaine, wheat in particular has large amounts, as do many plant- and animal- derived ingredients .

In a nutshell, choline in monogastric nutrition is ignored because there isn’t nearly enough information on either requirements or basal levels in feeds to be very precise. In lieu of good information, producers are forced to feed excesses. Some research funds to quantitate the relationships between interacting nutrients could prove fruitful in the long term.