Body composition analysis of chickens by dual energy x-ray absorptiometry

Dual-energy x-ray absorptiometry (DXA) was evaluated as a method for measuring the body composition of growing broiler chickens. A total of 130 chickens, ranging in weight from 400 to 3,290 g, were scanned using a DXA instrument (Lunar DPX-L). Single whole-body scans were acquired and analyzed using pediatric total body research software (neonatal mode) or small animal total body research software (detail or high resolution mode). The DXA measurements provided readings of total tissue mass, percentage fat, fat tissue mass, lean tissue mass, and bone mineral content. After scanning, the bodies of the chickens were frozen, then, after removing the feathers, homogenized for chemical determination of fat, water, and protein content. By chemical analysis, the whole body fat content of the chickens ranged from 2.8 to 27.2%, giving rise to DXA R values (ratio of attenuation coefficients) ranging from 1.415 to 1.339. The accuracy of DXA for measuring total body fat was a function of the scanning program and mode and also the size of the bird. The best agreement between DXA and chemical measurements of percentage body fat were obtained when chickens weighing more than 2,000 g were scanned using either the small animal-detail mode or neonatal mode. None of the scan modes proved to be accurate for measuring the fat content of birds weighing less than 2,000 g. The DXA measurement of lean mass of chickens was found to be highly correlated with both total body protein (R2 = 0.90) and total body water (R2 = 0.93), but was of little value for predicting percentage values for either. The ratio of DXA bone mineral content to total body ash was 0.77; however, the correlation (R2) between the two was only 0.46. These results suggest that although the DXA technique is potentially useful for measuring body composition of chickens, considerable refinement is needed prior to routine application.