Seventeen Arabian weanlings were used to determine the influence of housing on third metacarpal bone mass. Animals were separated into three treatment groups: Pasture (n = 6), Stall (n = 5), and Partial-Pasture (n = 6). Radiographs of the left third metacarpus were taken every 28 d to determine radiographic bone aluminum equivalence (RBAE). Serum was collected every 14 d and analyzed for osteocalcin, carboxyterminal telopeptide of type I collagen (ICTP), and keratan sulfate. Hip and wither height, BW, and cannon circumference were measured every 28 d. Lateral RBAE in the pastured group increased linearly from d 0 to d 56 (P = 0.001). In the Pasture group, total RBAE increased from d 0 to 56 (P = 0.05) and medial RBAE tended to increase from d 0 to d 28 (P = 0.06). The Partial Pasture group increased from d 0 to 56 in medial (P = 0.02) and tended to increase in total RBAE (P = 0.08). Although the Stall group demonstrated an increase in total RBAE from d 0 to 56 (P = 0.04), the Partial Pasture group tended to have greater total RBAE than the Stall group at d 28 (P = 0.08), and the Pasture group had greater lateral RBAE at d 28 (P = 0.005) and 56 (P = 0.007) than did the Stall group. At d 28, medial RBAE was greater in the Pasture (P = 0.003) and Partial Pasture (P = 0.05) groups than in the Stall group. Pasture and Stall groups tended to decrease in osteocalcin (P = 0.06), whereas Partial Pasture weanlings decreased (P = 0.01) from d 0 to 56. All treatment groups decreased from d 0 to 56 in ICTP (P < 0.01). Pastured weanlings decreased from d 0 to 42 in serum keratin sulfate (P < 0.05), whereas the Stall group decreased from d 0 to 56 (P = 0.05). All treatment groups increased in wither height (P ≤ 0.01), hip height (P ≤ 0.001), and BW (P ≤ 0.01). Both the Pasture and Partial Pasture weanlings demonstrated greater cannon circumference than Stall weanlings on d 28 (P ≤ 0.05) and 56 (P ≤ 0.005). These data demonstrate that pasture rearing or 12-h daily turnout is beneficial to maintaining and increasing bone mineral content in weanling Arabian horses.