Measurement of changes in body composition of piglets from birth to 4 kg using quantitative magnetic resonance (QMR)*
The purpose of this study was to use quantitative magnetic resonance (QMR) to measure changes in the body composition of piglets during growth from birth to 4 kg body weight. Using QMR, 60 pigs were scanned an average of 5 times starting at 2.7±1.3 days of age (1.95 kg) and finally at 13.1±4.3 days (4.14 kg). Regression analysis revealed that the rates of total body growth and fat and lean deposition were linear throughout this period. Subsequently, a second group of 235 pigs (109 males and 126 females) were scanned twice, first at 2.7±1.2 days of age and then at 13.4±3.1 days of age. The mean (±SD) rate of total body growth was 230±57 g/day. The rates of fat and lean deposition were 40±13 g/day and 191±52 g/day, respectively. The rates of both fat and lean deposition were highly correlated ( P<0.001) with total body growth rate (R 2=0.81 and 0.93, respectively) and the coefficient of determination between the rates of fat and lean deposition was 0.71 ( P<0.001). The results of this study demonstrate that QMR is a useful method for measuring changes in body composition in neonatal pigs. Furthermore, the results indicate that during the period of growth from birth to 4 kg, the rates of both fat and lean deposition are linear and highly correlated with total body growth.