A formal description of the growth and composition of bones in male and female broilers

1. This study measured the changes in weight, size, ash, calcium and phosphorus in the skeletons of growing broilers. Ross 308 broilers were sampled at intervals from hatch to 85 d of age. The selected birds were weighed individually, killed by cervical dislocation and defeathered.2. The skeleton of each bird was excised and defleshed and divided into its component bones which were weighed before and after drying and defatting. The length and width of the metatarsus, ulna, humerus, tibia and femur were measured. The ash content of each component of the skeleton was determined. Ca and P contents were measured in the humerus, tibia and pelvis ash of three birds of each sex.3. Gompertz parameters were determined for the feather-free body and for each of the components. Rates of maturing were maintained for all components within a sex, as these are allometrically related. The slope of the plots of the natural logarithms of skeleton ash and feather-free body weight suggested that the ratio between these increased with age and were predicted using allometry.4. Tibial Ca and P formed a constant proportion of ash in the tibia but these proportions were lower in the humerus and pelvis. Hence, caution must be applied when extrapolating tibia values to the contents of the entire skeleton. The proportion of ash found in the skeleton components changed as the broiler grew, which was in a manner that was predictable using allometry with body protein. Fluctuations in the ratio between ash and body protein over the growth period suggested that birds may not be reaching their potential skeleton mineralisation with the feeds provided.