Abstract :
An Hologic QDR4500A dual energy X-ray absorptiometer (DXA) was used to measure live
body composition in 15 second-cross wether lambs ((Border Leicester × Merino) × Poll
Dorset) aged 6–8 months (17–50 kg) and 13 mature ewes (composite terminal sire line
based largely on Poll Dorset, White Suffolk and Texel breeds) (44–71 kg). After slaughter,
DXA scans were also performed on the whole carcasses. Values determined by DXA including
total tissue mass (TTM), lean tissue mass (LTM), fat tissue mass (FTM) and bone mineral
content (BMC) for the half carcass were evaluated by comparison with chemically determined
composition. In the case of BMC the relationship was with chemically determined
ash content. Live weight and chemically determined lean, fat and ash were strongly related
to DXA-derived values for whole body TTM, LTM, FTM and BMC, respectively (R2 = 0.999,
0.988, 0.980 and 0.977, respectively). Carcass weight and chemically determined lean, fat
and ash were strongly related to DXA-derived values for carcass TTM, LTM, FTM and BMC,
respectively (R2 = 0.998, 0.984, 0.986 and 0.906, respectively). However, because DXA estimates
were different from chemically determined values in this sample of carcasses, they
needed to be adjusted with the use of appropriate regression equations to correct the inbuilt
algorithms used to predict human body composition. These data demonstrate the
efficacy of DXA as a non-destructive method for determining the composition of the whole
body and carcasses of sheep.
