Physical and mathematical modelling of the energy requirements of the outdoor sow
With the increase in recent years of the popularity of outdoor pig production systems throughout the UK, it is important to address the welfare and production issues which arise from this method of farming. Outdoor sows are exposed to widely varying environmental conditions which affect their heat loss. Temperature, radiation, windspeed and precipitation are all important variables affecting heat loss, as is the sow's use of available shelter. It is currently unclear as to the amount of additional feed required to compensate for the adverse weather conditions likely to be encountered outside. Outdoor sows may also require additional energy for the potential increased degree of activity. In order to be able to predict heat loss under different meterological conditions a mathematical model is necessary. This study constructs such a model to determine the energy requirements of the outdoor sow, taking into account the variable insulation provided by subcutaneous fat and other tissues and the extent to which shelter can modify the effects of the environment. The effect of these factors is assessed using physical models of outdoor sows to estimate heat loss as a result of different environmental conditions. A behaviour study was carried out to assess the use of available shelter by outdoor sows. The mathematical model then allows an assessment to be made of the welfare implications of outdoor production systems.