AMPK is a serine/threonine kinase considered as a key energy sensor. It regulates lipid and glucose metabolism. AMPK also controls reproductive functions such as gonadotropin secretion and steroids production in rodents. Here, we characterized AMPK in goat ovary, a small ruminant species. We also investigated the effect of metformin, a pharmacological activator of AMPK, on the Thr172 phosphorylation of AMPK (pAMPK) and progesterone secretion by cultured goat granulosa cells. Since polyunsaturated fatty acids (PUFAs) are known to modulate AMPK in different cell types, we finally studied the in vivo effect of two diets enriched in PUFAs on the AMPK subunits and pAMPK in goat ovary. Using RT-PCR and western-blot, we identified the messenger and the protein of the different AMPK subunits in adult goat ovary, small follicles (< 4 mm), large follicles (> 4 mm), granulosa cells, corpus luteum, oocyte, cumulus cells and muscle (as positive control). Interestingly, the AMPKb1 subunit was not expressed in the oocyte and the AMPKg3 subunit was only detected in muscle. Metformin (10 mM) increased by 2 to 3 fold pAMPK in granulosa cells from small follicles, from 5 to 120 minutes of stimulation (p<0.05). Metformin (10 mM, 48 heures) also inhibited progesterone secretion in both basal state by 30 % and under IGF-1 (10^-8 M) or FSH (5x10^-8 M) stimulation by 47 to 55 % (p<0.05). Finally, we studied the effect of two diets on the expression of AMPK subunits and pAMPK in goat ovary. One diet was enriched in a-linolenic acid (ALA, diet 1) and the other one was enriched in ALA, eicosapentaenoic acid and docosahexaenoic acid (diet 2). After slaughter, we dissected small and large ovarian follicles. The protein level of AMPKa1 and AMPKb1/b2 was not affected by these two diets. In contrast, protein level of AMPKg1 was increased by 1.5 fold and AMPKg2 was inhibited by 75 % by the diet 2 only in small follicles (p<0.05). pAMPK was inhibited by 28 to 56 % by the two diets in small follicles and was activated by 1.5 fold by the diet 1 in large follicles (p<0.05). So, the AMPK subunits, except for g3, are expressed in the different cell types of the goat ovary. Moreover, in cultured goat granulosa cells, metformin activated AMPK and reduced progesterone secretion. A diet enriched in PUFAs can modulate in vivo the expression of the AMPK subunits and pAMPK in goat ovarian follicles.