Fortpflanzungsphysiologie und assistierte Reproduktion beim Haushund (Canis familiaris) - eine Literaturstudie

The aim of this work was the evaluation of literature about
physiology of reproduction, assisted reproduction technologies and
associated biotechniques in domestic dogs (Canis familiaris). In
the bitch preovulatory follicular luteinization results in exposure
of oocytes to increasing concentrations of progesterone 1-2 days
prior to ovulation. Ovulation occurs approximately two days after
the LH-peak. The bitch ovulates primary oocytes with intact
germinal vesicle, which requires 2-5 days for the completion of the
meiotic divisions within the oviduct. Artificial insemination (AI)
in bitch can be performed either intravaginally or intrauterinely
with fresh, chilled or frozen-thawed spermatozoa. Intrauterine
insemination (IUI) may be carried out surgically by laparotomy or
laparoscopy or non-surgically using transcervical cathetherization.
In the bitch, IUI results in a high whelping rate and litter size
comparable to those after natural mating. Cryopreservation of dog
semen has been successfully accomplished and a variety of
extenders, freezing and thawing protocols have been published. AI
with cryopreserved semen generally yields lower pregnancy rates if
intravaginal deposition of semen is used. A reliable method for
synchronization and induction of a fertile oestrus cycle as well as
superovulation by hormone treatment are not available. Canine
oocytes may resume meiosis spontaneously in vitro, although at a
much lower efficiency than in most other domestic species. In vitro
maturation (IVM) of oocytes results in 20 to 70 % oocytes entering
germinal vesicle breakdown (GVBD). Only 10 to 40 % oocytes progress
to metaphase I to II. It has been shown, that cumulus morphology,
stage of estrous cycle, oocyte size, cumulus-oocyte communication
through gap junctions, age of oocyte donors, and serum
supplementation of the culture medium influence the efficiency of
IVM. Dog oocytes cultured within advanced preantral and early
antral follicles in vitro are competent to resume meiosis and
mature to the metaphase stage. The developmental potential of these
oocytes was comparable to isolated cumulus oocyte complexes. The
optimal culture conditions required for induction of capacitation
and acrosomal exocytosis of canine sperm are yet to be established.
Dog spermatozoa are able to penetrate the zona pellucida and the
vitellus of homologous oocytes irrespective of the oocyte
maturation stage. The developmental potential of fertilized dog
oocytes in vitro is very low. Only one case of development to the
blastocyst stage after in vitro fertilization (IVF) has been
reported. The surgical transfer of ex vivo collected dog embryos
resulted in birth of live puppys although the success rates were
low. Up to date no reports of production of live pups after IVF
from in vivo or in vitro matured dog oocytes exists. In one study
three conceptuses were identified by ultrasonography twenty days
after transfer of in vitro fertilised oocytes but no further
development could be observed. Reliable protocols for
cryopreservation of dog embryos have yet to be developed. Until
recently, there has been limited interest in assisted reproduction
techniques in the dogs. The rising significance of dogs as
companion animals as well as interest in comparative aspects with
wild-life canides will stimulate research in the fields of in vitro
production of embryos, cryopreservation and embryo transfer of
embryos.