The pig is a fast-growing animal with the potential of achieving more than a hundredfold increase in body weight before 12 months of age. For pigs to achieve this rapid weight increase, large quantities of nutrients are needed for tissue development. The rate of development of the major body components is changing continually, at least until the pig attains its mature size.
Body tissues with the highest rate of formation in younger pigs are bone and muscle.
Finisher pigs continue to deposit muscle and bone, but their rate of deposition declines, whereas body fat increases rapidly as body weight increases. Because pigs differ genetically in the rate and the development of these three major body components, the dietary nutrient requirements will reflect these changing body-development patterns. Figure 5 also compares the body-tissue development of two differing genotypes. There is generally a greater difference in body composition between genotypes during the finisher than during the grower period. Relative Rates of Body Development and Nutrients Needed at Various Production Phases.