Growth, development and chemical composition of the pig. IV. Relative growth of visceral organs.

The relative growth of the kidneys, spleen, liver, heart, lungs and G.I. tract were studied in a group of 90 pigs, serially slaughtered over a live weight range of 10 to 132 kilograms. The relationships between organ weights and body weight, body protein and body fat were examined by the allometric equation: Y = aXb, or in logarithmic terms: log Y = log a + b log X. The growth coefficients (b) of organ weights relative to body weight and body composition were similar for both sexes (P greater than .13), except that heart growth relative to body fat was significantly (P less than .04) higher for females (b = .54) than for castrated males (b = .50). A significant sex difference (P less than .05) in lung weight was also noted after adjustment to common body weight; there were no significant sex differences in organ weights after adjusting to common body protein and body fat. The spleen, heart and lungs grew at a faster rate relative to body weight and body composition than the kidneys, liver and digestive tract. The growth coefficients ranged from .44 to .87, indicating that the visceral organs develop at a slower rate relative to body weight and body composition.