Milling News
Choline in animal nutrition: Its role, sources and new approaches
A
by Carlos Lopez, Liptosa, Spain
lthough the first references to choline date from back in the nineteenth century, choline’s role in animal nutrition was not well known until 1930s. In 1850, Theodore Gobley already discovered lecithin, which was followed by the discovery of choline in 1862, when Mr Adolph Strecker heated lecithin from bile, which produced a new nitrogenous chemical. Since then, several researches have established choline to be an essential nutrient, which has four main functions (Zeissel 2006, Garrow 2007, Rajalekshmy 2010): 1. As a required constituent of phospholipids, choline is essential for building and maintaining cell structures, as well as to ensure the normal maturation of the cartilage matrix of the bone and prevent perosis in broilers 2. Choline plays an essential role in regulating fat metabolism in the liver, preventing abnormal accumulation of fat within hepatocytes (fatty liver) by increasing the utilisation of fatty acids in the liver 3. Choline is a precursor of acetyl choline synthesis, which makes possible the transmission of nerve impulses 4. Choline furnishes labile methyl groups for formation of methionine from homocysteine and of creatine from guanidoacetic acid. 5. Also, since choline contains biologically active methyl groups, methionine can serve as a partial alternative to choline. Although, in contrast with most vitamins, choline can be synthetised by most species, this synthesis is often insufficient to satisfy the animal´s needs, making choline an essential component of the diet. Choline is present in several feed ingredients traditionally used for feed formulation – 7374 mg/ kg DM rapeseed meal oil; 2899-3182 mg/kg DM soybean meal oil; 1743 mg/kg DM wheat meal; 1162 mg/kg DM barley; 617 mg/kg DM maize (INRACIRAD-AFZ tables), but little is known about its bioavailability and differences are expected based in crop growth conditions, treatment, season of the year etc. Therefore, to overcome the variation in raw material concentration and the uncertainty of bioavailability, an adequate choline supplementation is required, supplying both the essential and non-essential needs of different animal species. The most common choline source is choline chloride (CC),
66 | August 2020 - Milling and Grain
produced by chemical synthesis, by reaction of methanol and ammonia, which gives rise to trimethylamine (TMA) and subsequent reaction of this with ethylene oxide gives choline. CC is obtained by reacting choline with HCl. Commercially, CC is available in both, liquid and powder form, with differences regarding choline chloride content and equivalent choline activity studied extensively (See Figure 1). However, despite being widely used, chemical choline chloride has some disadvantages: Corrosivity: Liquid choline chloride is very corrosive, requiring special storage, transport and handling procedures. Additionally, choline chloride is highly destructive to vitamins, decreasing its stability in the premixes containing it (Coelho et al. reported Vitamin K retention in six months period was 57 percent lower in a vitamin premix containing CC than in a premix without it, and 50 percent, 40 percent and 37 percent lower retention for Vitamin C, B1 and A respectively) Higroscopicity: Chemical choline chloride is highly hygroscopic, attracting moisture to preparations containing it, which makes uniform mixing difficult, leading into fluidity problems in the final product TMA content: Trimethylamine content should be less than 200-300mg/Kg. Even if within the permitted levels, up to twothirds of the choline can be transformed into TMA during the digestion process, limiting the CC inclusion rate Inclusion rate: Only approximately one-third of the choline is absorbed, requiring a higher inclusion rate in the diet. Considering the problems faced by feed/premix manufacturers due to the above-mentioned disadvantages, new choline sources have emerged in the market as an alternative to the chemical choline chloride. Liptosa, a company specialising in the manufacturing of phytobiotics and nutraceutical solutions have launched recently Natur Colin, a product that serves as an effective replacement Figure 1: Nutritional values Choline chloride % Presentation
75
60
50
50
Liquid
Solid
Solid
Solid Mineral
Excipient
-
Vegetal
Vegetal
Humidity
25
2
2.5
12
Choline equivalent (activity) %
65
52
43
43
Cl %
19
15
12.5
12.5
N%
7.5
6
5
5
Source: FEDNA Figure 2: Dose-equivalences between Choline Chloride 60% and Natur Colin, for various purposes Natur Colin (gr/mt feed) CC 60% (gr/mt feed)
Replacement
Replacement Zootech improvement
300
100
120
600
200
240
1000
333
400
500
600
1500 Rate: 3:1
Rate: 2.5:1