Feed energy evaluation for growing pigs

Abstract

Pigs require energy for maintenance and productive purposes, and an accurate amount of available energy in feeds should be provided according to their energy requirement. Available energy in feeds for pigs has been characterized as DE, ME, or NE by considering sequential energy losses during digestion and metabolism from GE in feeds. Among these energy values, the NE system has been recognized as providing energy values of ingredients and diets that most closely describes the available energy to animals because it takes the heat increment from digestive utilization and metabolism of feeds into account. However, NE values for diets and individual ingredients are moving targets, and therefore, none of the NE systems are able to accurately predict truly available energy in feeds. The DE or ME values for feeds are important for predicting NE values, but depend on the growth stage of pigs (i.e., BW) due to the different abilities of nutrient digestion, especially for dietary fiber. The NE values are also influenced by both environment that affects NE requirement for maintenance (NEm) and the growth stage of pigs that differs in nutrient utilization (i.e., protein vs. lipid synthesis) in the body. Therefore, the interaction among animals, environment, and feed characteristics should be taken into consideration for advancing feed energy evaluation. A more mechanistic approach has been adopted in Denmark as potential physiological energy (PPE) for feeds, which is based on the theoretical biochemical utilization of energy in feeds for pigs. The PPE values are, therefore, believed to be independent of animals and environment. This review provides an overview over current knowledge on energy utilization and energy evaluation systems in feeds for growing pigs.

Keywords: Energy Utilization; Feed Energy Systems; Pigs.

Figure 1

Estimation of the energy requirement for maintenance from energy retention (kcal/BW^0.6/d) and energy intake (kcal/BW^0.6/d) in pigs. Adapted from de Lange and Birkett (2005). FHP = Fasting heat production.

Figure 2

An example of approximate energy utilization of growing pigs fed a corn-soybean meal-based feeds (Kil, 2008). NE_p = Netenergy for production.

Figure 3

Comparison of predicted NE values (kcal/kg) of 16 diets fed to finishing pigs from the French and Dutch NE system (if the dots are placed on the center line, the predicted values are identical between 2 systems).