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Procedures and methodology for determining the net energy content of feedstuffs
Feed is the single most expensive input in commercial pork production and a large portion of the cost associated with feed is related to supplying energy. Thus, there have been concerted efforts to develop methods and systems for evaluating the energy content of feed. In this regard, the net energy (NE) system, which takes into account the metabolic utilization of energy, has been proposed as a superior system for characterizing the energy value of feeds. Furthermore, the NE system allows for a more effective use of high fiber feedstuffs and may lead to reductions in feed cost. Various procedures and methods have been used to determination of NE in feeds and feedstuffs; the most common ones being the comparative slaughter (CS) and indirect calorimetry (IC) methods. Each of these methods has its advantages and disadvantages. For instance, although the CS method is regarded as the gold method, it is labor intensive, and requires a large number of animals. The IC method requires fewer animals, takes a relatively short period of time, and can be used for repeated measurement of energy balance, but it also requires sophisticated and often expensive equipment for the required gaseous exchange measurements. Nonetheless, the IC method is the most commonly used method for determining the NE content in swine feed and feedstuffs and require accurate estimation of energy lost as heat and the energy required for maintenance. These estimates, which are influenced by several factors including physiological status and activity level, have direct impact on the NE estimates obtained and therefore it is critical that these are accurately determined. For routine estimation of net energy content, however, prediction equations based on chemical composition measurements of feeds and feedstuffs have been suggested, although questions of acceptability for such equations still exists. In this presentation, the procedures and methods for estimation of NE in feeds and feedstuffs and considerations for design of experimental diet will be discussed. Results of recent studies comparing determined and predicted NE values will be highlighted.
Keywords: net energy, methodologies, feeds, feedstuffs, pigs