In vivo measurement of body composition of chickens using quantitative magnetic resonance

Quantitative magnetic resonance (QMR) is a nuclear magnetic resonance-based method for measuring the fat, lean, and water content of the total body of the live animal. The purpose of this study was to evaluate the use of QMR for measuring the body composition of chickens while comparing QMR results to those obtained by dual x-ray absorptiometry (DXA) and chemical analysis (CA). A total of 191 birds were scanned live (nonanesthetized) by QMR, killed, and then scanned by DXA. The birds were Ross 708 broiler chickens and ranged in weight from 786 to 3,130 g. In addition, 48 of the carcasses were chemically analyzed for total body lipid, water, and ash content. Compared with CA, QMR underestimated the percentage of total body fat by 34% whereas DXA overestimated the percentage of fat by 50% (10.35 ± 3.35 by CA vs. 6.73 ± 3.90 by QMR and 15.55 ± 4.01 by DXA; P < 0.05). Both QMR and DXA measurements of percentage total body fat were highly correlated with the CA measurement (R(2) = 0.94 and 0.68, respectively). Both QMR and DXA estimates of total body water were close to the CA measurement (1,166 ± 277 g by CA vs. 1,214 ± 279 g by QMR and 1,217 ± 255 g by DXA; P > 0.05), with R(2) values of 0.90 and 0.91, respectively. Based on regression analysis, when prediction equations were applied to the entire group of birds, the QMR and DXA measurements of total body water and total body lean mass were in good agreement, with no significant difference (1,125 ± 244 g vs. 1,135 ± 246 g and 1,377 ± 311 g vs. 1,403 ± 309 g, respectively; P > 0.05) and highly correlated (R(2) = 0.97 for both). Likewise, the QMR measurement of total body fat agreed closely with that measured by DXA (164 ± 48 g and 167 ± 47 g, respectively) and was highly correlated (R(2) = 0.72). The results of this study demonstrate that with proper calibration, both QMR and DXA can provide accurate measurements of the body composition of chickens. The major advantage of the QMR method is that no anesthesia is required, thus facilitating the ease of measurement and repeated measurements.