Abstract

OOCYTE QUALITY IN REPEAT-BREEDER DAIRY HEIFERS AND EFFECTS OF OPU ON REPRODUCTIVE PERFORMANCE R Båge1, S Petyim1, B Larsson1, T Hallap1, AS Bergqvist1, H Gustafsson2 and H Rodríguez-Martínez1; 1SLU, Uppsala, Sweden and 2Swedish Dairy Association, Eskilstuna, Sweden. Repeat-breeder heifers (RBH) deviate from normal considering hormonal interplay during estrus, with effects on estrus and ovulation (Båge R et al, Theriogenology 2002;57:2257-2269). This study evaluated the effect of repeated ovum pick-up (OPU) on RBH characteristics. The aims were to study 1) effects of OPU on estrous cyclicity, follicle development and oocyte recovery rate, 2) IVM and IVF competence and oocyte morphology after IVM, and 3) carry-over effects on fertility. Ten Swedish red and white-breed heifers were used: defined RBH, (n=5, average age 3.5 yrs, 3 AIs with returns to estrus within normal inter-estrous intervals) and virgin heifers (VH, controls, n=5, average age 2.7 yrs). Oocytes were retrieved by OPU performed twice weekly during 4 to 6 consecutive estrous cycles. OPU was restricted to the first 12 cycle days, starting after spontaneous ovulation of the pre-ovulatory follicle had occurred. A total of 269 RBH oocytes and 174 VH oocytes were collected. Oocytes were quality scored prior to conventional IVM and IVF. Ten immature and ten IVM oocytes from either category were fixed for morphology. Nuclear and mitochondrial changes after IVM were studied by laser confocal microscopy (LSM 510, Zeiss, Oberkuchen, Germany) after staining with propidium iodide and Mitotracker Green (Molecular Probes, Leiden, the Netherlands). Ultrastructure was studied by TEM (JEM-1230, JEOL Ltd., Akishima, Japan). At first estrus after OPU, the heifers were artificially inseminated. Plasma progesterone concentrations were analysed by RIA (Coat-A-Count®, Diagnostic Products Corporation, Los Angeles, CA) on cycle D0 (onset of standing estrus), 6, 12 and 16, plus D21 and 23 after AI. Pregnancy was confirmed by ultrasonography 30 days after AI. Frequency distributions were compared by Chi-square test, and a Mann-Whitney test or Wilcoxon Signed rank test were used for group-wise comparisons (Minitab software, Minitab® Release 10.2, Minitab Inc., PA). During OPU, RBH progesterone concentrations were higher (P<0.05) on D0, but lower (P<0.01) on D6, 12 and 16 compared to VH. Pre-ovulatory follicle diameter was greater (P<0.05) at ovulation in RBH. Estrus intensity and inter-estrus intervals were equal in RBH and VH, and unaffected by OPU (NS). There was no depletion of follicles over time (P<0.01) in RBH or VH. At quality scoring, more (P<0.05) oocytes were classified as good (grade 1-2) for VH (55%) than for RBH (42%). Cleavage rates after IVF were equal (NS) in RBH (33%) and VH (34%). Degree of chromatin condensation in immature oocytes (before GVBD) and after IVM (MI or MII) was similar in RBH and VH (NS), but spatial distribution of mitochondria and cortical granules after IVM was less advanced in RBH. Pregnancy rates after AI were comparable to field fertility (RBH 2/5, VH 4/5). In conclusion, an OPU schedule with physiological ovulation, CL formation and a third, unpunctured follicular wave does not change RBH characteristics concerning progesterone concentrations and pre-ovulatory follicle development. Correspondingly, control heifers were unaffected by this OPU regime. While nuclear maturation after IVM and cleavage rates after IVF were similar in RBH and VH, RBH showed a sub-optimal cytoplasmic maturation in vitro and the expected fertility after controlled AI. Supported by FORMAS and SLF, Stockholm. Dr. Nakao Takenouchi, Iwate, Japan, is acknowledged for information about the OPU schedule

Keywords

artificial insemination; bovine; confocal microscopy; electron microscopy; infertility; oocyte quality; progesterone

Published in

Theriogenology
2003, Volume: 59, number: 1
Publisher: Nagai Takashi, Piedrahita Jorge

Conference

Annual Conference of the International Embryo Transfer Society, IETS

SLU Authors

• Larsson, Birgitta

  • Department of Clinical Sciences, Swedish University of Agricultural Sciences
    

• Båge, Renee

  • Department of Clinical Sciences, Swedish University of Agricultural Sciences
    

• Bergqvist, Ann-Sofi

  • Department of Clinical Sciences, Swedish University of Agricultural Sciences
    

• Rodriguez, Heriberto

  • Department of Clinical Sciences, Swedish University of Agricultural Sciences
    

Permanent link to this page (URI)

https://res.slu.se/id/publ/236