Choline, an essential nutrient with health benefits in humans, is a main component of egg yolk. This article delves into the controversy surrounding choline supplementation in poultry feeds and presents two approaches to choline supplementation.
A key element for health
Choline is an essential nutrient for humans and many other animals including poultry. Choline was formerly classified as a B vitamin (vitamin B4). Layers, much like broilers, possess a crucial need for choline. One of its primary roles is synthesizing the phospholipid lecithin, a key constituent of egg yolk. Phospholipids refer to phosphorus-containing lipids that were first separated from egg yolk by Gobley in 1844 and named lecithin. The components of egg yolk lecithin include phosphatidylcholine (PC), phosphatidylethanolamine, and lysophosphatidyl choline. PC represents about 73% of lecithin content. Egg yolk lecithin is a basic component of special medicinal emulsions and has the potential to become a new generation of drugs. At present, egg yolk lecithin has been used to improve memory in schizophrenia, childhood autism, and Alzheimer’s disease.
Choline plays crucial roles in fat metabolism, nerve function, and the structural integrity of cell membranes. It helps prevent fatty liver syndrome in laying hens by modulating lipid metabolism, and it is considered as a powerful lipotropic agent. PC is the main constituent of very low-density lipoprotein (VLDL) that are required for fat transport from hepatic tissue to yolk through blood.
Choline controversy: How much to supplement?
A number of factors may influence a hen’s requirement for choline, for instance age, feed intake and dietary crude protein or methionine levels. The level of methionine is important because of the relationship with the choline. Choline and methionine are considered as methyl donor nutrients. Choline can be supplemented in addition to methionine, but will not spare the basic methionine requirements for protein synthesis. Numerous reports show that laying hens respond to choline supplementation. Choline exerts a sparing effect on methionine use for methyl group supply. A diet rich in Methionine + Cysteine (M+C) lowers the requirement for choline and vice versa. Laying hens will respond to supplemental choline in practical situations when diets are deficient in methionine and Total Sulfur Amino Acids.
The standard content corrected to choline chloride equivalent in various feedstuffs according to NRC (1994) is given in Table 1, and requirement of choline in Laying hens diet is given in Table 2.
Significant differences between published NRC (1994), and measured values (IEEB, 1997) are obvious in Table 1, with no indication of bioavailability of naturally occurring choline. Therefore, NRC tables for choline content of raw materials are not always valid and their contribution to dietary concentration might be over-estimated, and should be used with caution.
Note: NRC values are in choline hydroxide. They have been converted to choline chloride (equivalent multiply by 1.15). IEEB (Institute European de l’ Environment de Bordeaux, F-3300 Bordeaux); results are based on chemical analysis) are in choline hydroxide. They have been converted to choline chloride (equivalent multiply by 1.15).
According to NRC (1994) Table 2, Layers requires around 110 mg per day, equivalent to approximately 1,100 mg/kg of feed. Brown layers typically require slightly more than white layers due to their tendency to lay larger eggs. A typical diet based on corn and soybean meal (64 % corn, 25 % SBM, and 11 % other) will contain at least 1,000 mg/kg choline from natural sources. The same diet based on wheat and soybean meal will contain even higher amounts. Eventually, Layers hardly require any supplementation with either cereal source. Supplementation may therefore be viewed as a precaution against variable availability of choline from natural sources.
The need for choline supplementation to diets of laying hens has been a controversial issue for decades. However, Commercial recommendation consider higher requirements, and additional supplementation is essential, particularly for breeds of greater longevity and maintenance of healthy liver. Commercial choline chloride supplements are available on the market, and supplemental choline is routinely used in most poultry feeds.
Two schools of thoughts
Two approaches exist when addressing choline supplementation to diets. The first approach involves employing a high level of choline supplementation uniformly across all diets. For instance, this could entail adding 500 mg/kg in all layer diets. This method overlooks any variations in the natural choline levels present within or among cereal sources.
The second approach revolves around treating choline as a nutrient requiring careful balance and monitoring during formulation, considering specific contributions of choline from natural ingredients.
To Conclude
Choline is always beneficial for the birds in production and therefore must be included in layer diets. Adequate choline supplementation in layer diets will overcome the variations in raw material concentration, and the uncertainty of bioavailability.
In general, commercial recommendations for the choline content of laying hens’ diet are in the range 1200-1500 mg/kg. Given a baseline level of around 1000 mg/kg, this indicates that dietary supplementation with choline should ideally fall within the range of 200-500 mg/kg. A recently published article by Hendrix Genetics Layers 2020, advised to add choline in layer feeds in the range of 500- 1000 mg/kg, with 250 mg/kg being the minimum acceptable level. Factors that determine quantity of choline added are: the choice of raw materials, length of production period, birds’ liver health, and safety margins considered.
For more information about layer feed formulation, contact our technical team.