~A serial real-time ultrasonic measured of backfat and loin muscle area was recorded to examine the rate of change per unit of live weight during the finishing stage of production. Sixty-nine sets of 3 littermates (boar, gilt, and barrow one each) involving the 3 major breeds Duroc, Landrace, and Yorkshire in Taiwan were used in this study. Real-time ultrasonic measurements of backfat and loin muscle area were collected at average body weight (BW) of 57.2, 78.8, 94.2, 113.5, and 128.1 kg. Backfat was measured off the midline at the 3/4 point (TRBF) over the tenth rib. Loin muscle area (LMA) images were collected from the left side of each pig at the 10th rib. Deposition rates were calculated for the dependent ultrasound traits TRBF and LMA in models that included the independent variables BW and BW2. Body weight was regressed on age and age2 for growth rate (GR). The serial measurements data were analyzed using a mixed model (PROC MIXED, SAS) that included the fixed effects of test group, breed, sex, and random effect of animal. Significant breed effects were detected for deposition rate of TRBF (P = 0.0405), LMA (P = 0.0210), and GR (P = 0.0082). Backfat thickness was deposited at a mean of 0.109 mm/kg, whereas LMA was averaged 0.299 cm2/kg deposited across 3 breeds. Average GR across breeds was 677.3 g. Barrows deposited fat at a greater rate (P = 0.0220) and grew at a greater rate (P = 0.0462), when compared with gilts. However, barrows grew at a lesser rate (P = 0.0380) than boars. The results of this study indicated that effects of breed and sex play important roles for rates of backfat and loin muscle deposition and weight per day of age in swine, and therefore, breed- and sex-specific adjustment factor are required.