Linear models for Predicting body weight in crossbred chickens

Prediction of body weight with linear body measurements of 531day-old crossbred chickens was determined by stepwise regression analysis for mixed sexes at 4 and 8 weeks and separate sexes at 12, 16 and 20 weeks. Shank length was the best single predictor of body weight in Isa Brown x naked neck (IBxNa) at 4 weeks (coefficient of determination, R2 = 65%) and in feathered x Isa Brown (FxIB) at 8 weeks (R2 = 96%). In males, body weight was best predicted by drumstick length (DL) in IBxNa (R2 = 90%) at 12 weeks and in Isa Brown x frizzle feathered (IBxF) at 16 (R2 = 85%) and 20 (R2 = 81%) weeks. The best single predictors of body weight in females were body length (BL) (R2 = 91%), body girth (BG) (R2 = 90%) and body width (BW) (R2 = 90%) in naked neck x Isa Brown (NaxIB) at 12, 16 and 20 weeks, respectively. The best partial predictors of body weight were BG and wing length at 4 weeks (R2 =97%) and BG, BL and keel length (KL) at 8 weeks (R2 =97%) in IBxF; BW and DL (R2 =76%) in normal feathered x Isa Brown (NxIB) males at 16 weeks and BW and DL (R2 =97%) in NxIB females at 20 weeks. The higher R2 values obtained in the models for females made prediction of their body weight more accurate than that of the males. In general, the R2 of mixed sexes ranged from 50-97% and 62-97% at 4 and 8 weeks and for males and females, it ranged from 50-90% and 57-91%; 51-85% and 53-90%; 49-81% and 51-90% at 12, 16 and 20 weeks, respectively. Body weight was best predicted at 8 weeks, and irrespective of genotype, sex and age, the best predictors in single or partial state were BG, BL, KL, BW and DL.