Secretome is composed by proteins and microvesicles secreted by the granulosa cells that line the follicular wall. These bioactive compounds promote follicular growth and oocyte maturation, influencing oocyte metabolism. Hence, we hypothesized that addition of secretome from preovulatory follicular fluid (FF) to maturation medium may influence the meiotic competence and metabolism of cumulus-oocyte-complexes (COCs) obtained post mortem. FF was retrieved from preovulatory follicles (2 mares) after 32h of hCG administration. Three ml of FF from both mares were pooled, diluted 1:1 in PBS and centrifuged (4000g, 1h at 4°C) using a 10K Amicon® Ultra-15 Centrifugal Filter Unit and protein concentration was measured. A total of 186 COCs were retrieved from post mortem ovaries and were subjected to in vitro maturation (IVM) in TCM-199 medium, 10% of FBS and 5 mU/ml of FSH (Control; 59 oocytes) or with 20 µg/ml of secretome (Secretome20; 66 oocytes) or with 40 µg/ml of secretome (Secretome40; 61 oocytes) for 28 h in 5% CO2/95% air at 38.2°C. Oocytes were denuded, fixed in 4% formaldehyde and stained with Hoechst 33342 to assess chromatin conformation by fluorescence microscopy. Also, selected metabolites of the maturation medium prior to andafter IVM were assessed by magnetic proton nuclear resonance spectroscopy. After IVM, a trend towards glucose consumption and pyruvic acid production was observed compared to their controls prior IVM; a significant increase in lactic acid production in all treatments was observed (Table 1; p < 0.05). Our results show a tendency for quicker meiosis resumption in COCs incubated with Secretome40 (Table 2). In conclusion, secretome obtained from preovulatory follicular fluid added during IVM does not change COCs’ energy metabolism nor maturation rate of equine cumulus-oocyte complexes in our in vitro culture system. Funding: MCCIN/AEI (PID2020-112723RB-I00; RYC-2017-21545; RYC2020-028915-I), Junta de Extremadura-FEDER (IB20005).