Scientifi cally Speaking …
By Matthew Wedzerai
Matthew Wedzerai holds an MSc in Animal Science (Specialisation: Animal nutrition) from Wageningen University, The Netherlands. He also holds a Diploma in Pig husbandry & Animal Feed, PTC+ College, The Netherlands. He has 7 years’ experience in the pig husbandry and animal feed industry and has been a writer of articles based on scientific research since 2014.
CHOLINE IN POULTRY – REVISITED! Although choline is found in some feed ingredients, it remains essential that birds receive enough choline supplements to meet their total requirements for this vitamin. Latest studies (Jahanian et al., 2018) have highlighted more benefits of supplementing choline, especially to broiler diets. Most of these findings are presented in this article.
WHAT IS CHOLINE? Choline, is a water soluble colourless compound with vitamin-like properties; it is not 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 AVAILABILITY IN SOME FEEDSTUFFS Most of the standard choline chloride contents of feed ingredients, based on chemical analysis of crops, are given in NRC (1993) tables. However, it may be expected that variation in content of choline will occur due to variation in prevailing crop growth conditions. Emmert and Baker (1997) have estimated the bioavailability of choline naturally present in soybean, rapeseed and peanut meals, at 83, 24 and 76 % respectively. Due to differences in choline content, typical corn-based diets require more choline supplementation, compared to, for example, wheat-based diets.
FUNCTIONS OF CHOLINE The most important functions are: • It is a constituent of phospholipids; it is essential in the building and maintenance of cell structure, as well as ensuring normal maturation of the cartilage matrix of the bone, • It is important in the prevention in broilers, of perosis (a disorder of poultry that is characterized by leg deformity and is caused
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by a deficiency of vitamins (as biotin or choline) or minerals (as manganese). • It prevents fatty liver by increasing the utilisation and transport of fat, preventing abnormal accumulation of fat within hepatocytes. • It is a precursor for acetyl choline synthesis, the transmission agent for impulses along the sympathetic nervous system; regulation of protein synthesis • A point to note; growing chickens can use betaine interchangeably with choline for the methylation function, but it cannot replace choline to prevent perosis.
CHOLINE IN POULTRY Due to inability to synthesize at sufficient rate, young chickens need choline more. Choline requirement of growing chicks decreases with age. Females are said to be less susceptible to choline deficiency. It is an important component of the egg since eggs contain 12-13 mg choline per gram. White egg laying strains needs 1300, 900 and 500 mg choline/kg diet during 0-6, 6-12 week of age and 12 week to age at first egg, respectively and broilers need 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 birds (Rajalekshmy, 2010), whereas in broilers, it improves weight gain (Igwe et al., 2015), feed conversion efficiency (Hossain, et al., 2014; Igwe et al., 2015) and decreases serum cholesterol (Rahman, 2005). The symptoms of choline deficiency include reduced growth, fatty infiltration of liver and perosis in chicks (McDonald, 2011).
Broilers
Recommended levels In the study of Emmert and Baker (1997), using a choline-deficient basal diet, a close to linear response to incremental addition of choline chloride up to 1115 mg/kg feed in chicks from 10-22 days of age was observed. Increasing choline chloride to 2000 mg/kg resulted in further weight gain improvements, but to a lesser extent. At a feed intake of 100 g/day, a recommendation of 118 mg choline/day equates to a dietary requirement of 1180 mg/kg, which is similar to that of NRC (1994). According to Leeson and Summers (1991), recommendations for the choline content of layers feed are in the range 1200-1400 mg/ kg. Assuming a dietary background level of approximately 1000 mg/kg, this suggests the dietary supplementation with choline chloride should be in the range 250-500 mg/kg. In a broiler trial with day-old chicks (Jahanian et al 2018) consisting
of 3 dietary treatments (control, 1000 mg/kg of choline or 100 mg/kg of carnitine), the following observations on growth performance, meat quality and carcass yields were observed: Effect on performance Supplementation with choline and/or carnitine improved the FCR values during both the starter and finisher periods. The greatest impacts of this supplementation were observed during the finisher period, and effects were more pronounced by supplemental choline than with carnitine.
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