Abstract: Traditionally, body composition data for poultry is determined
by grinding /homogenizing the whole bird and obtaining a sample for wet chemistry
analysis. The overall process is slow, requires a large amount of freezer space
and the time-lag required for determining body composition reduces the opportunity
to use data in real- time situations. Two studies were conducted to evaluate
Dual-energy X-ray Absorptiometry (DEXA) as a means of measuring body composition
in broilers and broiler breeders. In Trial 1, two hundred and forty Cobb 500
broilers were reared from day-old to 60 days of age. Broilers were extracted
from the flock every 3 days during the 60 day grow-out in order to obtain a
variety of body weights and body composition for developing the body composition
equations. The birds were weighed and scanned using the small animal software
mode of the DEXA scanner (LunarProdigy, GE®).
DEXA provides measurements in grams of Bone Mineral Content (BMC), Fat Mass
(FM) and Lean Mass (LM). It was assumed that the sum of BMC+FM+LM represented
the total body mass. After the scan was performed, the carcasses were frozen
for further chemical analysis. Prior to chemical analysis, the carcasses were
thawed, autoclaved at 110°C with 1 atm pressure for 1-5 h depending upon
Body Weight (BW) and homogenized in a heavy duty blender (Waring Laboratory,
Blender LBC15, Model CB15). Samples of the homogenized carcasses were freeze
dried, weighed, ground and analyzed for total ash, ether extract and crude protein.
The measurements obtained from the DEXA scans were compared with the whole body
chemical analysis for each broiler. Regression analysis of DEXA values (BMC,
FM, LM) and chemical analysis (ash, ether extract and protein) were utilized
to determine possible correlations. Prediction equations were then developed
to adjust the original DEXA results to more accurately predict BMC, fat tissue
and lean mass. The R2 values for the prediction equations using DEXA
values were 0.999, 0.99, 0.96 and 0.99 for total mass, BMC, fat and lean mass
(P<0.0001). In Trial 2, 156 Cobb 500 broiler breeder hens were scanned to
validate the equations developed in Trial 1. The results indicate that the prediction
equations were adequate and a reliable alternative for measuring body composition
in broilers and broiler breeders. The high degree of correlation for all the
variables indicates that with proper calibration the DEXA values can be used
to predict body composition for these birds (R2 = 0.99, 9.99, 0.84
and 0.94 for total mass, BMC, FM and LM, respectively, p<0.001). |