Tri-State Swine Nutrition Guide : Pig Growth and Development
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 evelopment. The rate of development of the major body components is changing continually, at least until the pig attains its mature size.
Figure demonstrates the relative rates of formation of the major body components (bone, muscle, fat) from birth (3 to 4 lb.) to 300 pounds body weight. 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 also compares the body-tissue development of two differing genotypes. The "industry average" and the "lean" genotypes are depicted, but other genotypes with different development patterns are also present in the swine industry. There is generally a greater difference in body composition between genotypes during the finisher than during the grower period.
Bone development is more rapid in younger animals but declines as the animal reaches market weight. Because of this, a higher die-tary concentration of calcium and phosphorus is required for starter and grower than for finisher pigs. Although the rate of bone formation declines as the animal enters the latter stages of growth, the skeleton is still growing albeit at a slower rate. During the latter growth period, bones widen and become thicker and thus stronger. Finisher pigs therefore have the capacity to deposit calcium and phosphorus in their bone tissue beyond that needed to attain optimum growth responses. The need for the higher deposition of minerals in bone is not necessary for pigs destined for market, whereas gilts that are being retained for the breeding herd need to store additional minerals which can serve as reserves for later reproduction. Consequently, replacement gilts fed a finisher diet containing lower calcium and phosphorus concentrations will likely develop a weaker skeletal structure. Increasing the dietary calcium and phosphorus by 0.10% above that recommended for market swine will result in optimum bone mineralization in replacement animals.
Tri-State Swine Nutrition Guide : Vitamins & Water