The primary objective of this study was to determine whether exogenous arachidonic acid (AA) in a supplemented formula substitute for piglets or sow milk would attenuate reductions in AA status, growth, and bone mineral content (BMC) as a result of exogenous glucocorticoid excess using dexamethasone (DEX). A secondary objective was to confirm a positive effect of exogenous AA on growth and BMC of piglets fed formula and not treated with DEX as well as to determine whether the elevation in BMC was related to greater production of prostaglandin E(2) in bone. Forty-eight 5-d-old male piglets were randomized to be suckled or receive either a standard formula or the same formula, but containing AA (0.5% wt/wt total fat) for 15 d in addition to either treatment with DEX or placebo. Piglets treated with DEX grew slower and had lower BMC of whole body, lumbar spine, and femur in addition to lower proportions of AA, but those fed standard formula had the greatest reductions. Piglets in the supplemented group weighed more than piglets fed standard formula or suckled in both the DEX and placebo groups. Suckled piglets had the highest BMC of whole body and femur compared with standard formula, and the supplemented group was intermediate for whole body but similar to suckled pigs for femur. Release of prostaglandin E(2) was elevated only with supplementation of AA. These data indicate that supplemental AA is associated with elevated whole body and femur BMC but that BMC is not enhanced during glucocorticoid treatment.