ROLE OF CHOLINE CHLORIDE IN POULTRY (LAYERS & BROILERS) FEED
Choline chloride is used as an important feed additive in animal species, especially chickens.
Choline- chemically known as 2-hydroxyethyl-trimethyl ammonium hydroxide and is referred as vitamin B4. It has recently been claimed as a rediscovered vitamin & performance promoter in poultry. The role of choline in the prevention of conditions such as perosis and liver enlargement in chicks is already well known. Choline was first isolated from ox bile (“chole” in Greek) in 1849. Its nutritional importance has been recognized since 1930 and it is now a common dietary supplement for livestock & poultry. The main function of choline is to act as a lipotropic agent and prevents the abnormal fatty infiltration in liver (Fatty Liver Syndrome) thus ensures proper metabolism of the body & effective utilization of the nutrients. Moreover, it helps in the formation of an excitatory neurotransmitter-acetylcholine, which is responsible for proper functioning of the nervous system and maintains its harmony.
Choline, is a water-soluble colorless compound with vitamin-like properties as not a metabolic catalyst but forms an essential structural component of body tissues (McDonald et al., 2011). Choline is ubiquitously distributed in all plant and animal cells, mostly in the form of the phospholipids, phosphatidylcholine (lecithin), lysophosphatidylcholine, choline plasmalogens and sphingomyelin – essential components of all membranes (Zeisel, 1990). Choline degrades in hot alkali creating trimethylamine. Choline has ability to form salts with many organic and inorganic acids. It is well soluble in water and ethanol, but not in ether. Choline is chemically a strong alkali and hygroscopic nature. Choline is amino ethyl alcohol and have three methyl groups on the nitrogen atom, chemically termed as (2- Hydroxyethyl) trimethylammonium. Chemical formula of choline is C5H14NO+ and of choline chloride is (HOCH2CH2N (CH3)3HCl). Cholinechloride have 139.63 g/mole molecular weight, 2470 c melting point, decompose on heating, 1.1 g/cm³ relative density at 20 °C (70% choline chloride in water) and practically stable at 20-300C.
Choline is present in the unsupplemented diet mainly in the form of lecithin, with less than 10% present either as the free base or as sphingomyelin. Choline is released from lecithin and sphingomyelin by digestive enzymes of the gastrointestinal tract, although 50% of ingested lecithin enters the thoracic duct intact (Chan, 1991). Both pancreatic secretions and intestinal mucosal cells contain enzymes capable of hydrolyzing lecithin in the diet. Within the gut mucosal cell, phospholipase A1 cleaves the alpha-fatty acid, and phospholipase B cleaves both fatty acids. Quantitatively, digestion by pancreatic lipase is the most important process.
Functions of choline chloride are
1. building and maintaining cell structures,
2. fat metabolism of the liver,
3. formation of acetylcholine (essential) and
4. methyl-group donor (non-essential) via betaine.
1. Choline is a metabolic essential for building and maintaining cell structure. Choline is a structural part of lecithin (phosphatidylcholine), certain plasmalogens and the sphingomyelins. Lecithin is a part of animal cell membranes and lipid transport moieties in cell plasma membranes. Phospholipids are present in the cell membrane bilayers, and the primary function of these phospholipids are to regulate cell membrane integrity and porosity. Choline is required as a constituent of the phospholipids needed for normal maturation of the cartilage matrix of the bone.
2. Choline is referred to as a “lipotropic” factor due to its function of acting on fat metabolism by hastening removal or decreasing deposition of fat in liver. Choline plays an essential role in fat metabolism in the liver. It prevents abnormal accumulation of fat (fatty livers) by promoting its transport as lipoprotein and lecithin or by increasing the utilization of fatty acids in the liver.
3. Choline is essential for the synthesis of acetylcholine by mitochondriaat the presynaptic terminal of the neural synapse, a substance that makes possible the transmission of nerve impulses.
4. Choline is a source of labile methyl groups. Choline furnishes labile methyl groups for formation of methionine from homocystine (Figure) and of creatine from guanidoacetic acid. The pathways of choline and 1-carbon metabolism intersect at the formation of methionine from homocysteine. Methionine is regenerated from homocysteine in a reaction catalyzed by betaine: homocysteinemethyl transferase, in which betaine, a metabolite of choline, serves as the methyl donor (Finkelstein et al., 1982). To be a source of methyl groups, choline must be converted to betaine, which has been shown to perform methylation functions. Since choline contains biologically active methyl groups, methionine can partly be spared by choline and homocysteine. Research with lactating dairy cattle suggests that a high proportion of dietary methionine is used for choline synthesis (Erdman and Sharma, 1991; Benoit et al., 2010). The amino acid methionine is the source of the methyl donor S-adenosyl methionine, the metabolite that provides methyl groups in a variety of reactions including the de novo synthesis of choline from phosphatidylethanolamine. When choline is oxidized irreversibly to betaine, betaine can provide methyl groups that recycle homocysteine to methionine
CHOLINE IN POULTRY
The young chicken needs choline more due to inability to synthesize at sufficient rate. Female are less susceptible to choline deficiency, without exact clear mechanism. Egg contains 12-13 mg choline per gram dried whole egg mass. The bird needs 20,00-30,00 mgcholine /kg diet to induce toxicity (Leeson and Summers, 2001). White egg laying strain needs 1300, 900 and 500 mg choline/kg diet during 0-6, 6-12 week of age and 12 weeks to age at first egg, respectively and broiler needs 1300, 1000 and 750 mg/kg diet during 0-3, 3-6 and 6-8 week of age, respectively (NRC, 1994). Choline supplementation improves egg production in layer bird (Rajalekshmy, 2010), whereas weight gain (Igwe et al., 2015), feed conversion efficiency (Hossain, et al., 2014; Igwe et al., 2015) and decrease serum cholesterol (Rahman, 2005) in broiler. The supplementation of choline chloride at recommended rate is optimum for various production parameters. The supplementation of choline chloride @ 2000 mg/kg diet improved weight gain and feed conversion efficiency in quail (Alagawany et al., 2015). Symptoms of choline deficiency include reduced growth, fatty infiltration of liver andperosis in chicks.
CHOLINE CHLORIDE – DIETARY REQUIREMENTS OF BROILERS
Choline supplementation in broilers shows a linear response in weight gain up to 1115mg/kg from 10-22 days of age. Increasing choline content up to 2000mg/kg further increases the weight gain but over and above this value no significant increase in weight gain was observed. Thus, it could be concluded that excess level of choline supplementation had no additional benefit.
CHOLINE CHLORIDE – DIETARY REQUIREMENTS OF LAYERS
Layers, like broilers, have an essential requirement for choline. Choline is required for the formation of a phospholipid lecithin, a component of egg yolk. Current NRC recommendations for choline allowances in laying hens are 105 mg/day for white egg layers and 115 mg/day for those laying brown eggs. On an average for the two groups, it can be concluded that required dietary concentration of choline at feed intake levels of 100 and 110 g/day respectively, is approximately 1100 mg/kg.
There are several factors which influence a hen’s requirement for choline, like age, feed intake and dietary crude protein or methionine levels. It is generally accepted that dietary requirement declines with age, possibly associated with an increasing feed intake. Methionine is the first limiting amino acid for egg production and, given the common function with choline in methyl group donation, interactions between the two nutrients may be anticipated. Choline requirement in layers also varies according to the methionine and cysteine levels in feed. A diet rich in M+C has low requirement of choline and vice-versa.
SALIENT FEATURES OF AN IDEAL CHOLINE CHLORIDE:
1. Low Trimethylamine (TMA) content
2. High Bioavailability
3. Uniform particle size
4. Free from any toxin/contaminant
High Trimethylamine content causes toxicity in birds:
The most important & limiting raw material, which decides the quality of the product, is Trimethylamine (TMA), which is highly corrosive in nature. If its level exceeds beyond the permissible limit i.e.,>200ppm then it causes toxicity in birds. Due to its corrosive action, it causes sloughing of the intestinal mucosa & results into malabsorption (reduced nutrient utilization). Moreover, the fumes generated by TMA when enter the respiratory tract of the bird leads to discomfort that restricts the birds from feeding & ultimately it results into reduced production and may cause even death. So the TMA content in the choline chloride should be low to prevent toxicity and better production.
Bioavailability is the most important parameter, which should be taken into account while selecting an ideal choline chloride. Each carrier particle (corncob) should contain 60% of choline if analysed for its purity.
Uniform Particle Size:
Bioavailability is also attributed to the particle size of the carrier material. The ideal particle size for broilers is 0.3mm while for layers it is 0.5mm. The size should match with the feed in order to prevent selective feeding & to ensure uniform mixing.
No bacterial/toxin contamination:
Since the carrier material used for the production of dry choline chloride is corncob-agro byproduct, which is very much liable to be contaminated with various microorganisms. So, it should be thoroughly checked for the presence of any bacterial contamination like E. coli & Salmonella, as poultry is highly susceptible for these pathogenic microorganisms, which leads to reduced production and mortality in flock.
Choline Nutritional Requirements
The choline requirements for chickens range from 200 to 700 mg/kg of the diet. Generally, adult chickens are thought to synthesize the vitamin in adequate quantities. Feeding young chicks, a diet with excess dietary protein or high in fat increases their choline requirement. Age/Life Stage mg/kg Newly Hatched Chicks (0 – 10 wks) 200-400 Young & Growing (10 – 20 wks) 200-400 Laying hens (Actively laying eggs) 300-500 Breeders (20 wks & older) * 300-500 Broiler/’Meat’ Breed Chicks (0-18 wks) 350-700 Broiler/’Meat’ Breeds* (19 wks & older) 350-700
Global specification of choline chloride:
Description Yellowish brown coloured & granular powder
Choline Chloride %(w/w) NLT 60
Moisture (%w/w) NMT 03
Particle retention on mesh 20 ASTM /18 BSS (%w/w) NMT 20
Density (Tapped) g/ml 0.4 to 0.6
Trimethylamine Content (ppm) NMT 200