Daily access to pasture turnout prevents loss of mineral in the third metacarpus of Arabian weanlings

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). Radio graphs of the left third metacarpus were taken every 28 d to determine radi ographic bone aluminum equivalence (RBAE). Serum was collected every 14 d a nd analyzed for osteocalcin, carboxyterminal telopeptide of type I collagen (ICTP), and keratan sulfate. Hip and wither height, BW, and cannon circumf erence were measured every 28 d. Lateral RBAE in the pastured group increas ed 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). Alth ough 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 tha n the Stall group at d 28 (P = 0.08), and the Pasture group had greater lat eral 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 Pas ture (P = 0.05) groups than in the Stall group. Pasture and Stall groups te nded to decrease in osteocalcin (P = 0.06), whereas Partial Pasture weanlin gs 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 (IB less than or equal to 0.01), hip height (P less than or equal to 0.001), an d BW (P less than or equal to 0.01). Both the Pasture and Partial Pasture w eanlings demonstrated greater cannon circumference than Stall weanlings on d 28 (P less than or equal to 0.05) and 56 (P less than or equal to 0.005). These data demonstrate that pasture rearing or 12-h daily turnout is benef icial to maintaining and increasing bone mineral content in weanling Arabia n horses.