Domestic Animal Endocrinology 33 (2007) 281–293 Food deprivation stimulates the luteolytic capacity in the gilt Giovanna Galeati ∗ , Monica Forni, Nadia Govoni, Marcella Spinaci, Augusta Zannoni, Marco De Ambrogi, Sara Volpe, Eraldo Seren, Carlo Tamanini Dipartimento di Morfofisiologia Veterinaria e Produzioni Animali (DIMORFIPA), Universit` a di Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia (BO), Italy Received 16 January 2006; received in revised form 19 June 2006; accepted 19 June 2006 Abstract The aims of this study were to study the effects of fasting on progesterone (P4) production in the pig and to verify whether fasting influences luteal expression of PGF 2 receptor (FPr) and prostaglandin secretion. Superovulated prepubertal gilts were used; half of them were fasted for 72 h starting on day 2 (F2) or 9 (F9) of the induced estrous cycle, respectively, while two groups (C2 and C9) served as respective controls. Plasma P4 and PGFM concentrations were determined by RIA while FPr mRNA expression in CLs collected at the end of fasting period was measured by real-time PCR. In experiment 1, plasma P4 concentrations in fasted gilts were significantly (P < 0.01) higher than in controls starting from day 3 (F2; n = 6) and 10 (F9; n = 6). FPr mRNA expression was similar in F2 and C2 (n = 6) CLs while it was significantly (P < 0.05) higher in F9 than in C9 (n = 6) CLs. In experiment 2, cloprostenol administered on day 12 significantly (P < 0.05) increased FPr mRNA expression in CLs from both F9 (n = 6) and C9 (n = 6) gilts. At the time of cloprostenol injection PGFM levels were significantly higher (P < 0.05) in the fasted group and cloprostenol-induced luteolysis in fasted but not in normally fed gilts. Results from this study indicate that fasting in prepubertal gilts induced to ovulate stimulates luteal P4 and PGFM production as well as FPr mRNA expression, thus increasing luteolytic susceptibility. © 2006 Elsevier Inc. All rights reserved. Keywords: Fasting; Gilt; Luteolysis; Prostaglandin; Progesterone ∗ Corresponding author. Tel.: +39 051 2097910; fax: +39 051 2097899. E-mail address: ggaleati@vet.unibo.it (G. Galeati). 0739-7240/$ – see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.domaniend.2006.06.003