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. 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.
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.
Article made possible through the contribution of Kemin.