Relationship between the rate of longitudinal bone growth and physeal thickness in the growing fowl.

The thickness of the physeal cartilage (growth plate) was measured and the rate of longitudinal bone growth estimated in the femur, tibiotarsus and tarsometatarsus of different groups of domestic fowl. Birds were either a laying strain or broiler strain fed ad libitum, or a broiler strain on restricted feed. They were killed at different ages from hatching to 10 weeks and the mean thickness of the physeal cartilage and the mean estimated rate of longitudinal bone growth was calculated in the proximal bone extremities. Mean physeal thickness varied from 0.185 to 0.825 mm and longitudinal growth rates between 1.85 and 8.4 mm per week. When growth rates were plotted against physeal thickness the resulting scatter diagram suggested a positive linear relationship between the two. This study provides a range of baseline values for the assessment of proximal physeal thickness in other groups of fowl.