FEED Business Worldwide - April, 2011
How lysophospholipids improve the apparent metabolisable energy (AME) in broiler diets
by Bindhu Lakshmibai VASANTHAKUMARI, K.V. CHANDRASEKAR & V. RAVINDRAN
Fats are added to animal feeds to enhance dietary energy density, which leads to increased energy intake and, as a consequence, improved productivity. The addition of fat to diets, besides supplying energy, improves the absorption of fat-soluble vitamins and improves the palatability of the rations. Furthermore, the presence of fat reduces the passage rate of the digesta in the gastrointestinal tract, facilitating better absorption of dietary nutrients.
The efficient utilization of dietary fat requires digestion and absorption of fat in the gastrointestinal tract. The mechanism of fat digestion consists of three sequential steps, namely: (i) emulsification of fat (ii) lipase-catalyzed hydrolysis of fats to fatty acids and monoglycerides at the emulsion-water interface, and (iii) absorption of fatty acids through the intestinal villi (Figure 1). Owing to the insoluble nature of fat in the aqueous phase of digesta, emulsification step is a necessary process in lipid digestion. The rate-limiting step for fat absorption is diffusion through the "unstirred water layer" that lines the microvilli. The size of the micelles formed also determines their absorption by the villi (figure 2).
Bile salts function to emulsify fat to form fat-containing micelles to ease absorption from the intestinal tract. However, in animals, the production of bile salts is limited at birth and during early stages of development. Studies in poultry have indicated that fat digestion is low at early ages due to poor emulsification rather than deficiencies in lipase activity and this has led to considerable interest in the use of emulsifiers as a means of improving the utilization of fats in young birds. Lyso-phospholipids play a significant role in animal nutrition as powerful biosurfactants. The combination of lipophilic and hydrophilic properties of Lysophospholipids allows them to act as biosurfactants when mixed with water and fat. Dietary supplementation of Lysophospholipids has been shown to increase the digestibility and absorption of fat in young chicks and weaning piglets by improving the fat emulsification.
Lysophospholipids formed by the hydrolysis of phospholipids are more hydrophilic than phospholipids because they only have one fatty acid residue per molecule. Hence, lysophospholipids not only have good emulsifying capability inherent in the phospholipids but also capable of forming spherical micelles in an aqueous solution to solubilize water-insoluble substances in transparent state, unlike phospholipids. This property translates to improved emulsification efficacy which makes them better candidates for use in 'oil in water' emulsions such as that occuring in the gastrointestinal tract.
Lysophospholipids also possess the capability to form micelles spontaneously with bile salts, fatty acids and monoglycerides. Lyso-phosphatidylcholine together with linoleic acid has been reported to form very small and stable emulsions of ovalbumin compared with those of phosphatidylcholine. In fact, there exists a hypothesis that if lecithin was not hydrolyzed, the mixed micelles would be abnormal, and the absorption of free fatty acids would be depressed. To test this hypothesis, isolated segments of rat small intestine were infused in vivo with micellar solutions of linoleic acid and taurocholate to which was added 1-palmitoyl, 2-oleoyl lecithin, or 1-palmitoyl lysolecithin (the hydrolytic product of lecithin). Lecithin was found to depress the rate of free fatty acid absorption by 40% in jejunal and ileal segments whereas lysolecithin was associated with normal rates of free fatty acid absorption.
LYSOFORTEâ„¢brand Dry, a biosurfactant nutricine enriched with lysophospholipids, is extremely effective in improving the absorption of oils and fats from feed by the animal. The following unique properties of LYSOFORTE are responsible for the observed efficiency in increasing the rate and efficiency of fat digestion and absorption:
enhanced emulsification leading to the formation of smaller fat/oil droplets in the small intestine, providing more surface area for lipase activity, and
- easier micelle formation due to the very low critical micellar concentration (CMC) of lysophospholipids.
LYSOFORTEâ„¢brand Dry is widely used in animal diets to increase the digestion and absorption of oils and fats and to improve animal performance and feed efficiency. The better weight gains and energy sparing effects exhibited by LYSOFORTE in studies conducted all over the world, highlight the potential for a partial oil or fat replacement application. Research studies in Europe, South East Asia, India and China have demonstrated that LYSOFORTE addition can compensate for up to 8 to 10 kg of oil or fat in broiler diets. This effect is due to enhanced emulsification and absorption of fat from the feed that translates to an increased metabolisable energy of the feed. To further quantify the positive energy sparing effect of LYSOFORTE, a broiler apparent metabolizable energy (AME) bioassay was conducted at Massey University, New Zealand using diets containing 3 different fat sources. This paper summarizes the results of the assay on the effects of LYSOFORTE on the AME of diets containing tallow, palm oil or rice bran oil.
Materials & methods
The AME assay was carried out at the Monogastric Research Centre, Massey University (Palmerston North, New Zealand). The trial was conducted on 28-day old, male Ross 308 birds. Each treatment had 24 birds divided into 6 replicates, with 4 birds per replicate housed in a single cage. The following nine treatments were assayed for AME using the classical total excreta collection method (Table 1). The composition of the normal and reduced ME diets for each fat source is shown in Tables 2 to 4.
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