The
birds fed 500 IU/kg VD3 from 1 to 21 d and 22 to 42 d
had maximal tibial strength and density (54.97% and
38.18%, 81.05% and 37.36%, greater than those of the
controls, P < 0.05), and maximal values at d 63 resulted
from 600 IU/kg VD3; further responses to higher doses
were minimal.