The levels of
VD3 that maximized and appeared to reach a plateau
for bone strength and density were calculated to be
521 and 528 IU/kg of the diet, respectively; slightly
higher than the 500 IU/kg factorial estimate from 1 to
21 d. These regression-derived optima were 582 and 604
IU/kg for 22 to 42 d and 640 and 658 IU/kg for 43 to
63 d.