The NRC released their new edition of Nutritional Requirements for Swine in 2012, and has made updates to reflect the increase nutritional demand of modern pigs. Like previous editions, the values are based off of mathematical models, and the guide comes with software to run the models on at-home computers. Models were created for grower-finish pigs, gestating sows, and lactating sows. Energy utilization has become even more important due to rising feed costs, and NRC emphasizes the use of net energy in determining energy utilization. Literature reviews provide data for dietary energy of specific ingredients, which differs from the French or Dutch systems. NRC also confirms that energy requirements listed do not take into account environmental and animal variables, and that more accurate energy requirements can be predicted by also using the observed animal performance in a facility. The updated guide has a more complex method of predicting amino acid requirement that uses basal gut losses, skin and hair losses, and minimum urinary N loss. The use of co-products in feed often increases fibre, and as a response NRC published the changing threonine requirement when fibre increases in a diet. As well, the models show the changing amino acid requirements throughout the different stages of gestation and lactation, and information for intact males. Some of the limitation of the NRC values are that it does not incorporate nutritional history, or between-animal variation, and cannot be used for cost-benefit analysis. Overall, NRC has addressed many if the current and upcoming nutritional changes, and remains a valuable tool to estimate nutritional information and requirements.