1. Performance, gait score (GS), tibial dyschondroplasia (TD), and tibia bone mineralisation and breaking strength were determined in 2880 male and female Ross 208 broilers fed on diets with two different concentrations of dietary metabolisable energy (ME) (11·00 or 12·00 MJ/kg) and 4 different concentrations of available phosphorus (aP) adjusted for dietary ME content (4·0, 4·5, 5·0 or 5·5 g/kg aP in starter and 3·5, 4·0, 4·5 or 5·0 g/kg aP in finisher diets containing 12·00 MJ/kg).

2. Tibia ash, calcium (Ca) and phosphorus (P) contents in broilers given diets with low ME (11·00 MJ/kg) were greater than those of broilers given diets with higher ME (12·00 MJ/kg). Tibia ash, Ca and P contents increased curvilinearly with increasing dietary aP content. The dietary aP level had no effect on GS.

3. Dietary concentration of ME or aP had no effect on tibia breaking strength.

4. Walking ability, as measured by GS, was negatively correlated with the body weight (BW) of tested birds at 23 and 35 d of age, but the dietary ME content or aP level had no significant effect on GS at 35 d of age.

5. The results indicated that bone mineral content had no clear correlation with the walking ability of broilers.