Fat digestion and metabolism: effect of different fat sources and fat mobilisers in broilers’ diet on growth performance and physiological parameters – A review

Commercial broilers have a short production cycle and a high requirement for energy (3000 kcal/kg in starter phase and 3200 kcal/kg in finisher phase). Therefore, the need to add energy rich lipids to their diet is inevitable. Digestibility of fat depends on its multiple properties: chain length, the composition of fatty acids, ratio of saturated/unsaturated fatty acids and free fatty acids. The high cost of vegetable oils and less availability due to their consumption in human diet are the main reasons for searching for cheaper alternative fat sources. Animal oils like poultry and fish oil are the by-product of rendering plants and after refining, they are used in poultry diets as an energy source. Due to presence of impurities and free fatty acids, the digestibility of animal fat is lower. There is a limited amount of bile acids and lipase available during early age and when birds are reared on high energy diet (finisher phase). Supplementation of emulsifier or lipase in broilers’ diet increase fat utilisation. Emulsifiers increase fat digestibility by increasing active surface area of lipid droplets. Lysolecithin and lysophospholipids are produced from hydrolyses of lecithin and phospholipids by phopholipase A2. The bile acids are mainly composed of cholic acid, hyodeoxycholic acid and chenodeoxycholic acid and have strong emulsification properties. Triacylglyceryl acylase (lipase) is an enzyme involved in catalysis and the hydrolysis of lipids. It can be concluded that use of emulsifier and lipase in broiler diet improves growth performance, nutrient digestibility and intestinal histology in broilers.