Pigs of differing genetic development potentials for the three major body components (bone, muscle, fat) have different nutrient requirements. Nutritional requirements for the leaner genotypes require more amino acids for muscle tissue deposition, but the formation of lean tissue also requires additional vitamins and minerals. As pigs mature and as the rate of their body components changes, the diet fed should reflect the pigs' changing requirements for nutrients. For example, younger grower pigs have a high rate of bone growth and therefore have a higher calcium and phosphorus requirement. The requirement for these minerals declines as the pig matures, because the rate of bone formation declines. If an accurate quantitative estimate of the three body component tissues could be determined during each stage of growth for each genetic line, we would be able to more accurately formulate diets that would more closely meet the pig's nutritional requirements. Computer modeling systems using information about the pig's changing composition and accurate information about the "available" nutrients in the diet will be used in the future for diet formulations.
Frequent changing of the pig's diet (phase feeding) will more clearly meet the specific nutrient requirements at the various stages of body development. Phase feeding reduces the oversupply of nutrients provided compared to situations where diets are changed less frequently. Dietary formulations, however, should be matched to the genetic potential of the pig. As specific information becomes available about the rate of bone, muscle, and fat formation for different genetic lines, and as pigs become more uniform within their feeding group, frequent diet changes (phase feeding) can be successfully implemented.