Fats in poultry nutrition: Digestive physiology and factors influencing their utilisation

• Digestion and absorption of fat is a complex process.
• Emulsification is central to efficient fat digestion.
• Digestion is strongly related to the chemical structure of fats.
• The metabolisable energy of fat sources is variable.
• Nutritional emulsifiers can improve fat utilisation.

Fats and oils possess the highest caloric density of all known nutrients. In recent years, because of the ever-increasing energy costs, there is greater interest in maximising the use supplemental fats as nutritionists strive to increase the dietary energy density to meet the requirements of high-performing contemporary birds. To maximise their energy yielding potential, there is a need to better understand the physiological basis and factors affecting fat digestion. Compared to other macronutrients, the digestion and absorption of fats is a complex process and involve sequence of physicochemical events requiring breakdown to fat droplets, emulsification, lipolysis and micelle formation. Current knowledge of the principles of fat digestion and absorption in poultry is reviewed, along with factors influencing available energy content of supplemental fats. The supplemental fats are one of the most difficult ingredients to evaluate in terms of available energy. Important variables influencing the energy content of fats include age of the birds, degree of fat saturation, chain length, free fatty acids and fat inclusion level. Potential strategies to improve fat utilisation in poultry diets are also examined.