The effects of FSH, LH, and epidermal growth factor (EGF) on the dynamics of nuclear maturation and subsequent embryo development were examined in pig oocytes cultured either conventionally or after preincubation with cycloheximide (CHX). In conventional culture, FSH or EGF significantly increased the rate of attainment of metaphase II (MII) for both gilt (50.0%+/-4.2% and 54.8%+/-4.3%, respectively; control, 5.8%+/-1.8%; P<0.001) and sow (87.6%+/-3.4% and 78.8%+/-3.9%, respectively; control, 7.8%+/-2.5%; P<0.001) oocytes. Gilt oocytes treated with both FSH and EGF showed an additive response (93.7%+/-2.1%). Treatment with LH had no effect. Preincubation with CHX caused the majority (84-100%) of both gilt and sow oocytes to undergo germinal vesicle breakdown. Compared to those treated with LH and/or EGF (both>80%), fewer FSH-treated oocytes reached metaphase I (43.8%+/-5.3%, P<0.001) by 14 h and MII (48.4%+/-5.9%, P<0.001) by 24 h, although the majority (71%) did mature to MII by 36 h after removal of CHX. After in vitro fertilization, higher proportions of both CHX-pretreated and untreated, FSH-exposed oocytes cleaved (71.3%+/-2.9% and 75.3%+/-3.1%, respectively) compared with those not treated with FSH (37.7%+/-3.0% and 43.0%+/-2.9%, respectively; P<0.001). Pretreatment with CHX significantly increased blastocyst yield for both FSH-treated (32.8%+/-2.0% and 10.3%+/-1.5%, respectively; P<0.001) and untreated (16.7%+/-1.5% and 9.4%+/-1.2%, respectively; P<0.001) oocytes. Polyspermy rates were unaffected. In conclusion, pig oocytes meiotically arrested by CHX before maturation retain and improve their developmental competence. FSH stimulates nuclear maturation but slows meiotic progression.

The superstimulation protocol of Blondin et al. (2002; Biol. Reprod. 66, 38-43) produces cumulus-oocyte complexes (COCs) of high developmental competence for IVP. Using a similar protocol we assessed the affects of alterations in oocyte donor carbohydrate and lipid metabolism during ovarian stimulation on the production and viability of blastocysts in vitro. A 2 × 2 factorial experiment offered two diets: Fiber (F) and Starch (S) alone (0) or with 6% w/w (6) protected lipid (calcium soaps of fatty acids). Thirty-two heifers ranked by body condition score (scale: 1 = thin, 5 = obese) were allocated within score to one of the 4 treatments: F0, F6, S0 and S6. COCs were collected 5 days after estrus by OPU for lipid analysis. Ovarian stimulation (4 doses of FSH (9 mg NIADDK oFSH) given 12 h apart) commenced 2 days later. COCs were collected 40 h after the last FSH injection. GnRH (0.012 mg Buserelin) was administered i.v. 6 h prior to OPU. A second period of ovarian stimulation and OPU then followed. Following IVM/IVF, zygotes were cultured in SOF with 0.3% w/v fatty acid-free BSA under oil (38.8 • C, 5% CO 2 , 5% O 2 , 90% N) until Day 8 of development, when blastocysts were subjected to total cell counts and TUNEL analysis. Data were analyzed by ANOVA. Neither follicles aspirated (25.9 ± 1.87) nor oocytes recovered (12.1 ± 0.92) differed between treatments. Total fatty acids in plasma were greater (P < 0.001) for the F than for the S diets and increased with the inclusion of protected lipid (0.75, 1.82, 0.50 and 1.39 µg mL −1 for F0, F6, S0 and S6, respectively; SED = 0.076). The dietary lipid-induced increase in plasma fatty acids was reflected in an increase (P < 0.05) in total fatty acids within the oocyte (70.4, 74.7, 69.9 and 78.4 ng/oocyte; SED = 3.41). Retrospective analysis by body condition indicated that S diets reduced (P = 0.006) blastocyst yields in thin heifers and reduced (P = 0.02) cleavage rates in fat heifers (Table 1). Blastocyst yields were lower (P = 0.1) for fat heifers on the F0 diet. Total cell numbers