443 BIOLOGICAL FACTORS AFFECTING OOCYTE COLLECTION AND EMBRYOS PRODUCTION IN A COMMERCIAL OVUM PICKUP-IVP SYSTEM IN HOLSTEIN AND MONTBELIARD BREEDS

Abstract

The aim of this work was to identify biological factors affecting oocyte collection, embryo production, and subsequent pregnancy rates through a retrospective study conducted from 381 commercial ovum pickup (OPU)-IVP sessions performed on high genetic Holstein and Montbeliard donors. Oocytes were retrieved using an ultrasound scanner SC 200 (Pie Medical, Maastricht, the Netherlands) equipped with a 7.5-MHz annular-array transducer. Donors were superovulated at Day 12 of presynchronized cycle with FSH (Stimufol^®, Rhone-Merieux, Lyon, France) divided in 5 decreasing doses over 2.5 days. Cumulus-oocyte complexes (COCs) were collected 12h after last FSH injection and matured for 22 h in TCM-199 HEPES plus FCS, FSH, estradiol, and EGF They were then fertilized in fert-TALP with frozen-thawed semen. Zygotes were cultured for 6 days on a monolayer of Vero cells in B2 medium. Day 7 embryos were transferred as fresh into recipients. The effects of donor breed, dominant follicle puncture (DFP), and physiological state of females on oocyte and embryo production were analyzed by ANOVA (proc GLM, SAS Institute, Cary, NC, USA). From all collected animals, most (80.6%) of the donors were cows (55% collected as early pregnant and 31.9% previously infertile) and 19.4% were heifers (from those 86.5% pregnant). The mean number of collected COCs per session was 13.3 ± 8.3 (mean ± SD), 57.8% of which had ≥3 layers of cumulus cells (grades 1 and 2). A mean of 10.8 ± 6.9 COCs were subjected to IVM-IVF-IVC, which resulted in 3.5 ± 3.5 blastocysts per session (77% were graded as 1 and 2) whereas 2.8 ± 2.5 embryos were transferred into recipients. An overall pregnancy rate of 50.4% (544/1080) was obtained at Day 90: 59.1%, 50.4%, and 27.9% for grade 1, grade 2, and grade 3 blastocysts, respectively. The OPU sessions resulted in at least one Day 90 pregnancy in 61.2% of the cases. Breed had no effect on the number of collected COCs but a higher percentage of grade 1 and 2 COCs were observed for Montbeliard than for Holstein donors (60 v. 53%). Dominant follicle puncture 48 h prior to superovulation treatment significantly increased the number of COCs (15.7 ± 9.9 v. 10.9 ± 5.6; P < 0.05), the number of developed and transferred embryos and the number of pregnancies per session (4 ± 33.9 v. 7 ± 2.8; 3.3 ± 2.6 v. 2.4 ± 2.4; 1.7 ± 1.6 v. 1.2 ± 1.4, respectively). This effect was particularly impressive for Montbeliard heifers. Higher numbers of COCs were collected from infertile cows, nonpregnant cows as for early pregnant heifers (16.9 ± 10.4; 13.8 ± 7.6, and 13.8 ± 8.6, respectively) when compared with pregnant cows and nonpregnant heifers (11.0 ± 6.1; 10.5 ± 6.6; P < 0.05). The mean number of developed embryos was also influenced by parity of the donor and was 4.5 ± 4.5; 3.4 ± 3.7; 3.1 ± 2.8 for infertile, nonpregnant, and pregnant cows and 3.0 ± 3.4 and 2.5 ± 2.3 for pregnant and nonpregnant heifers, respectively. In conclusion, oocyte collection and embryo production were mainly influenced by parity and physiological status of Holstein and Montbeliard donors. Puncture of dominant follicle at the start of superovulation treatment increased the overall quantity of COCs and improved the efficiency of the IVP procedure.