Effect of donor age on the developmental capacity of bovine cumulus oocyte complexes obtained by repeated OPU from nonstimulated and FSH-superstimulated German Simmental heifers and cows at different life cycle stages

Similarities between the bovine female and women in terms of
reproduction and fertility, such as oogenesis, folliculogenesis and
reduced fertility with advanced age make the bovine a valuable
model for the study of ovarian function and dysfunction as well as
reproductive aging in women. The aim of the present work was to
investigate the influence of donor age on follicle numbers, yield
and quality of COCs obtained by repeated OPU and on the
developmental competence in vitro after oocyte maturation in vitro
versus in vivo. Further, the ability of oocytes from different age
classes to reprogram nuclei of bovine fetal fibroblasts was
studied. Since the individual is a major factor influencing
parameters of fertility and results of ART in both humans and
cattle, the present study used in parts the same animals to rule
out inter-individual effects on the response to one or the other
approach. Experiment 1 investigated the effect of donor age in
non-superstimulated German Simmental heifers (n = 12, 14 months at
the beginning of the experiments), young cows in their first
lactation (n = 8, 2-4 years) and old cows (n = 8, 10-15 years). A
total of 38 OPU sessions were performed in two experimental periods
on independent sets of animals from all age classes: 5/5/5 (32
sessions) and 7/3/3 (6 sessions). In spite of a marked influence of
the experimental period, a number of parameters were also
significantly affected by donor age. The total number of follicles
increased with age (P