Variability in bone mineralization among purebred lines of meat-type chickens

The variability of bone traits was assessed in purebred lines of meat-type chickens using dual-energy x-ray absorptiometry. Experiment 1 evaluated changes in bone mineralization and size traits of the tibia and humerus in 4 purebred lines from 6 to 24 wk of age. Experiment 2 compared the same traits of the tibia, radius, and ulna of 9 purebred lines at 6 wk of age. Differences in bone traits among purebred lines were apparent in both experiments. Of the 4 purebred lines compared in experiment 1, line C demonstrated the best phenotypic traits relative to bone quality. Even though line C had the longest tibia, one of the largest bone areas, one of the heaviest BW, and one of the highest bone mineral content (BMC) at 24 wk of age, the tibia of line C did not become less dense in mineral as this line of chickens approached sexual maturity as did the tibia of the other purebred lines of chickens. Specifically, its tibial bone mineral density (BMD) showed age-related increases unlike the other purebred lines of chickens, which showed little change in tibial BMD from 6 to 24 wk of age. In experiment 2, all bone traits as well as BW were different among purebred lines (P<0.001). The 2 purebred lines (7 and 8) with the lightest 6-wk-old BW (2,033 and 2,055 g, respectively) had diverse skeletal traits. Birds of line 7 had the lowest BMD (0.1131 g/cm2), BMC (1.05 g), shortest bone length (69.2 mm), and smallest bone area (8.0 cm2); however, the other purebred line low in BW (line 8) showed the opposite trend in that bones from these birds were the highest in BMD (0.1276 g/cm2), BMC (1.38 g), bone length (74.6 mm), and area (9.2 cm2) when compared with all of the other lines. In conclusion, several purebred lines of meat-type chickens expressed large differences in bone traits, suggesting the potential to genetically select birds for increased BMD.