Nutritional Manipulation and Interpretation of Body Compositional Differences in Growing Swine

Summary

The body composition of pigs depends on their genetic background, live weight and sex, but it is also highly influenced by nutrition. Daily body protein formation increases up to 40 to 60 kg live weight, plateaus from 60 up to 120 kg and then decreases towards zero. Daily body fat formation increases almost linearly with increasing body weight and feeding intensity. The percentage of physical dissected muscle and subcutaneous fat in the carcasses varies also with weight and feeding intensity. Female pigs contain more muscle, protein and water in the carcasses than do male castrates. An optimum rate of protein formation occurs only if the animal's daily intakes of essential nutrients and energy are sufficient. Insufficient protein intake reduces growth rate, feed conversion efficiency and meatiness of carcasses. Excess protein intake improves meatiness of carcasses, but it usually reduces daily gain and feed efficiency (gain to feed ratio). Energy intake above that necessary for maintenance and maximal muscle formation increases fat formation. Insufficient energy supply results in satisfactory meatiness of the carcasses, but growth rate and feed efficiency deteriorate. Production of lean and uniform carcasses requires diets optimized for essential nutrients in relation to energy. In terms of energy and protein, the nutritional value of diets should be based on net energy and digestible amino acids. Properly balanced diets, i.e., optimized on basis of net energy and digestible amino acids, have no direct influence on body composition. In pigs fed balanced diets and slaughtered at 90 kg live weight, approximately 55% of the deposited protein and 30% of the deposited fat was found in the muscle of the carcasses.

© American Society of Animal Science 1984