The major cost of poultry feed is energy, accounting for more than 70% of the feed costs. Therefore, accurate formulation of feed energy with adequate ingredient energy values is paramount for the effective formulation of poultry feed. Currently, apparent metabolizable energy (AME) is still used to assess the available energy in ingredients and feed for poultry. However, the limitations of AME have been recognized since the 1940s. Net energy (NE), the energy system measuring the actual energy used for maintenance and production, is more accurate for the feed formulation to meet the requirement of the animals, which has been used in other animals such as ruminants and swine. In poultry, the use of the net energy system has been halted due to the difficulty in achieving accurate measurement of NE or, more exactly, the inability to predict NE for feed and ingredients. Also, the benefit of using NE vs AME has not been demonstrated on a large scale or conceptually accepted by many poultry nutritionists. Henceforth, there is a need to ensure the NE values are accurately measured and predicted so as to make the application of the NE system in poultry production realized in the near future. Herein, this presentation will discuss the approaches for the measurements or prediction of NE of diets and ingredients for poultry from a methodological point of view. The indirect calorimetric system, using both closed and opened circuit chambers, has been used to measure the heat production of animals. Then accurate NE values of diets can be achieved by simultaneously measuring the AME of the feed with a total excreta collection method. Potentially, the NE values of ingredients can also be measured, albeit caution must be made to avoid flawed design and calculations. The NE of ingredients and feed can be calculated with available prediction equations, such as those recently published, given the available key nutrient composition and AME values. Particular attention should be drawn to the accuracy of diet and ingredient AME values for such prediction, as AME accounts for a large proportion of the calculation for NE. The NE requirement levels for different poultry are another important aspect of implementing the NE in poultry in this presentation. In addition, the potential of using table values and near-infrared spectroscopy will also be discussed.
Overall, NE has been considered an accurate energy system for feed formulation and practical approaches to estimate NE of ingredients and feed available for poultry.