Estimating body weight and body composition of chickens by using noninvasive measurements

The major objective of this research was to develop equations to estimate B W and body composition using measurements taken with inexpensive instrument s. We used five groups of chickens that were created with different genetic stocks and feeding programs. Four of the five groups were from broiler gen etic stock, and one was from sex-linked heavy layers. The goal was to sampl e six males from each group when the group weight was 1.20, 1.75, and 2.30 kg. Each male was weighed and measured for back length, pelvis width, circu mference, breast width, keel length, and abdominal skinfold thickness. A cl oth tape measure, calipers, and skinfold calipers were used for measurement . Chickens were scanned for total body electrical conductivity (TOBEC) befo re being euthanized and frozen. Six females were selected at weights simila r to those for males and were measured in the same way. Each whole chicken was ground, and a portion of ground material of each was used to measure wa ter, fat, ash, and energy content. Multiple linear regression was used to estimate BW from body measurements. The best single measurement was pelvis width, with an R-2 = 0.67. Inclusion of three body measurements in an equation resulted in R-2 = 0.78 and the f ollowing equation: BW (g) = -930.0 + 68.5 (breast, cm) + 48.5 (circumferenc e, cm) + 62.8 (pelvis, cm). The best single measurement to estimate body fat was abdominal skinfold thi ckness, expressed as a natural logarithm. Inclusion of weight and skinfold thickness resulted in R-2 = 0.63 for body fat according to the following eq uation: fat (%) = 24.83 + 6.75 (skinfold, In cm) - 3.87 (wt, kg). Inclusion of the result of TOBEC and the effect of sex improved the R2 to 0.78 for b ody fat. Regression analysis was used to develop additional equations, base d on fat, to estimate water and energy contents of the body. The body water content (%)= 72.1 - 0.60 (body fat, %), and body energy (kcal/g) = 1.097 0.080 (body fat, %). The results of the present study indicated that the c omposition of a chicken's body could be estimated from the models that were developed.