268 INFLUENCE OF DONOR AGE ON DEVELOPMENTAL COMPETENCE OF IN VITRO v. IN VIVO MATURED BOVINE OOCYTES OBTAINED BY REPEATED OVUM PICKUP FROM FOLLICLE-STIMULATING-HORMONE-STIMULATED AND NONSTIMULATED ANIMALS

Abstract

Recent findings on oogenesis, folliculogenesis, and ovarian aging in cows make the bovine system an attractive model for elucidating ovarian function and dysfunction as well as reproductive aging in women. The aim of the present study was to investigate the influence of donor age on the developmental competence of in vitro v. in vivo matured bovine cumulus–oocyte complexes (COC) obtained by ultrasound-guided repeated ovum pickup (OPU). Two groups (G1 and G2) of German Simmental heifers (14 months old at the beginning of the experiment, n = 5 and n = 7), first-lactation young cows (2–4 y old, n = 5 and n = 3), and old cows (10–15 y old, n = 5 and n = 3) were subjected to twice-weekly OPU without hormonal prestimulation 32 (G1) and 6 times (G2). Afterward, animals in G1 were punctured at 5-week intervals 9 times after FSH superstimulation to obtain in vivo matured COC at the metaphase II stage. Data were analysed using a mixed model (SAS). In the twice-weekly OPU for G1 and G2 combined, significantly (P < 0.05) more COC per animal and OPU session were obtained from the old cows (9.9 ± 1.0) compared with heifers and young cows (6.0 ± 0.8 and 7.0 ± 1.0, respectively). When G1 and G2 were regarded separately, lower numbers of COC (P < 0.01) were obtained in G1 than in G2 (2.7 ± 0.8, 4.4 ± 0.8, 7.0 ± 0.8 and 9.2 ± 1.5, 9.4 ± 2.3, 12.9 ± 2.3 for heifers, young cows, and old cows of G1 and G2, respectively). Cleavage rates (CR) on day 3 after IVF (day 0) were not affected by donor age and were not different between groups. Cultivation of COC from young cows in G1 led to higher blastocyst rates (BR) on day 7 (P < 0.05) compared with old cows and heifers. No differences in BR were observed between animals of G2. Significantly more COC (P < 0.01) were obtained in all age groups from FSH superstimulated donors (10.6 ± 0.8, 9.0 ± 0.9, and 11.7 ± 0.9 for heifers, young cows, and old cows, respectively). Cleavage rates and BR were significantly higher (P < 0.05) in all age groups after FSH superstimulation compared with those of nonstimulated donors. However, there were no differences in CR and BR between age groups (CR: 82.8 ± 7.0, 89.9 ± 7.0, 77.1 ± 6.2%; BR: 34.4 ± 7.2, 44.6 ± 7.2, 36.7 ± 7.2%). We conclude that although the numbers of COC obtained per animal and session were significantly different between G1 and G2, in vitro results were highly repeatable after OPU without hormonal prestimulation. Higher CR and BR were obtained after IVF of in vivo matured COC obtained from FSH superstimulated donors, regardless of animal age.