A model has been developed to provide estimates of nutrient flows within an outdoor pig farm that is consistent with the scope of OVERSEER® Nutrient Budgets (OVERSEER). The primary focus was on nitrogen (N). The model uses standard industry information as inputs to define the number of animals for different classes and their performance. The amount of feed brought in to the farm system and its quality is user defined or based on default values. Feed utilisation (including bird loss) is defined by the feeding method. The outdoor pig unit is divided into management areas (areas for lactating, mating, and growers and finishers, and an acclimatisation area for replacements). Sows use huts, and can be placed in village’s pre or post farrowing, and any pig class can be placed in sheds or barns as a means to reduce excreta deposition on the block. The model includes waste management options for the bedding and excreta from each form of housing. The nutrient flow and excreta deposited in each management area is estimated. For N, leaching losses were highly dependent on the stock density (the amount of feed intake) and the amount of pasture cover. Pasture cover was dependent on management (for example, stock density, placement and movement of troughs and huts, nose ringing) and hence pasture cover for each
