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Conference abstract2003

Collection and preservation of female gametes and embryos

Båge, Renee

Abstract

Collection and preservation of female gametes and embryos Renée Båge Dept of Obstetrics and Gynaecology, P.O. Box 7039, SLU, SE-75007 Uppsala, Sweden Centre for Reproductive Biology in Uppsala, CRU e-mail: renee.bage@og.slu.se In the transition from traditional, small-scale farming to intensive production there is usually a rapid change in the domestic animal population. Local breeds will become mixed with or displaced by commercial, high-performance breeds. For many reasons, it is necessary to preserve the native breeds. It is important to maintain genetic diversity and to recognize the qualities of the native breeds concerning their adaptation to the local conditions as well as their potential use in agricultural niche production. Economic conditions and market requirements can change in the future and the genetic merits of the old breeds may again be in demand. According to the Rio de Janeiro convention from 1992, all countries should make up plans and programs for conservation of animal genetic resources and promote their sustainable utilisation. Genetic resources can be conserved both for direct use and, by long term preservation, for future use. Rare breeds may be preserved in situ, in living herds, for the immediate use to improve livestock populations. In short- and long-term perspectives, assisted reproduction techniques can be used for the collection of gametes and production of offspring. Cryopreservation can be applied to preserve the produced gametes and embryos in genetic resource banks. Some of the techniques available are artificial insemination (AI), multiple ovulation and embryo transfer (MOET), collection of immature oocytes from ovaries of animals after slaughter or from live animals by transvaginal oocyte recovery (so-called ovum pick-up, OPU), in vitro maturation and fertilization of oocytes and in vitro culture of embryos, micromanipulation for the production of twins embryos or clones by nuclear transfer, intracytoplasmic sperm injection (ICSI), sperm sexing, and cryopreservation of gonad tissue for in vitro development of gametes. Some of these techniques are since long in commercial use (mainly in the bovine species), but many remain to be further developed before they can be used on a large scale. There may also be considerable species differences with respect to reproduction and sensitivity to the various techniques. The most commonly used reproductive techniques in the bovine species are presented below:  AI: Despite the progressive advances in the science of quantitative and molecular genetics, AI still remains one of the most important (and cost effective) assisted reproductive technologies. It is an important tool for dissemination of genes achieved in selective breeding programmes, in combination with more advanced reproductive techniques.  MOET: Where normally only one oocyte develops to ovulation per oestrous cycle, hormonal stimulation renders numerous oocytes from one female that can be fertilised and develop into embryos. During the 20 years that the technique has been in use, gradual improvements in the procedures result in increased numbers of viable embryos produced by session. Still, the numbers and quality of embryos varies greatly (the average is 5 per session), and there are physiological limitations to how frequent a selected donor female can be used. It is common with unwanted side effects from the hormonal treatment, and about 20% of the donors do not respond to the given treatment at all.  OPU: The most flexible and repeatable technique to produce embryos from a donor cow is OPU. Immature oocytes are collected and submitted to in vitro maturation, fertilisation and embryo culture, resulting in an in vitro-produced (IVP) embryo. With a twice-weekly puncture scheme, or, alternatively, collection of oocytes every 2 weeks after hormonal stimulation there is an average of 2 transferable embryos produced per session. The calving rate of IVP embryos is however lower than that of MOET embryos and the incidence of dystocia and malformations is higher.  Cryopreservation: By cryopreservation, organic tissue can be preserved for an infinite time, and cryopreservation of spermatozoa and embryos is a well established method, with successful freezing of bovine embryos since the early 1980s. There are two main procedures in cryopreservation, slow-rate freezing and vitrification. Slow-rate freezing of embryos in either glycerol or ethylene glycol has been the routine method for several years, but the interest for vitrification is advancing increasingly. It has turned out to work exceptionally well for extra sensitive embryos, i.e. early stage embryos and IVP- and micromanipulated embryos. Cryopreserved IVP embryos generally have 10-20% lower pregnancy rate than fresh embryos and perform more poorly than MOET embryos. Cryosurvival is also reduced in micromanipulated embryos. Porcine embryos are more chill sensitive due to their high lipid content, but improved protocols have recently resulted in live offspring born. Equine embryos with their unique embryology still present a challenge for cryopreservation. Oocytes are extremely chill sensitive, and successful cryopreservation is a highly topical research subject. The most plentiful source of oocytes is ovarian tissue, as it is containing many thousands of primordial follicles in the cortical tissue. Cryopreservation of primordial follicles and ovarian tissue for further culture in vitro in the future thus represents another opportunity to preserve female gametes, but it is still highly experimental and far from being clinically applicable

Keywords

Artificial insemination; Cryopreservation; Gene bank; MOET; Native breeds; OPU;

Published in

ISBN: 91-576-6593-1
Publisher: Centre for Reproductive Biology in Uppsala, CRU

Conference

Farm animal reproduction: Conserving local genetic resources

    UKÄ Subject classification

    Animal and Dairy Science
    Veterinary Science

    Permanent link to this page (URI)

    https://res.slu.se/id/publ/248