There are 2 steps in defining a feeding strategy. The first is to set reproductive targets including the amount of weight gain for sows during different parities and the number of piglets a sow should nurse during lactation. The second step is to set nutritional requirements to meet these specific targets. Models developed for sow nutrition requirements in gestation, attempt to partition nutrient requirements into three components: maintenance, growth of the conceptus and reproductive tissue. These models have led to the factorial approach to defining nutrient requirements in gestating sows.