Ovarian Activity and Oocyte Development during Follicular Development in Pigs at Different Reproductive Phases Estimated by the Repeated Endoscopic Method

The aim of the present study was to assess follicular and oocyte development in the same gilts during three phases of their reproductive life [prepuberal gilts (PP; 6.0 months of age), puberal gilts (P; 9.5 months of age) and primiparous sows (S)]. Follicular development was stimulated by the injection of 1,000 IU of equine chorionic gonadotropin (eCG) followed by 500 IU of human chorionic gonadotropin (hCG) 72 h later. Cumulus-oocyte-complexes (COCs) were recovered by endoscopic ovum pick up/aspiration from preovulatory follicles of the left ovary, and the follicular fluid (FF) from the right ovary was collected 34 h after the hCG treatment by endoscopy. Altogether, 19 pigs were used in the PP and P trials and 12 in the S trial. From the left ovaries, 168, 190 and 82 follicles were aspirated and 106, 125 and 42 COCs, respectively, were recovered (recovery rate 61 ± 27, 63 ± 21 and 53 ± 22%, respectively). The mean number of follicles was greater in the P phase than in the PP phase (19.7 ± 6.8 vs. 15.7 ± 6.8; p=0.06) and S phases (14.2 ± 4.0; p