Ghrelin is modified by fatty acid at the third serine residue. In this study, derivation of fatty acid for acylation of ghrelin was investigated using a hatchling chicken model. We first studied ghrelin gene expression and production in the neonatal chick proventriculus and then investigated the effect of exogenous octanoic acid (OA) administration on acylated ghrelin production. In a free-feeding condition on day 2.5 after hatching, the density of ghrelin mRNA-expressing (ghrelin-ex) cells was greater than that of ghrelin-immunopositive (ghrelin-ip) cells, but no difference was found between those densities in adult chickens. Intraperitoneal or oral administration of OA for a few days significantly increased the density of ghrelin-ip cells without any changes in ghrelin-ex cells and elevated only octanoylated ghrelin levels in the proventriculus. The results indicate that fatty acid absorbed from food is directly utilized in acylated ghrelin production in the chicken. (c) 2005 Elsevier Inc. All rights reserved.