Use of embryos for improvement and dissemination of genetics

The possibility to use embryo technology in pig breeding would be beneficial to increase biosecurity, animal welfare and genetic gain. The Norwegian Duroc sire line has on average 9.7 total number piglets born per litter compared to 14.3 piglets in the Norwegian Landrace dam line. Breed differences within this trait could be related to ovarian characteristics, which may also affect in vitro embryo production. This could require different optimizations to successfully obtain in vitro blastocysts in both breeds. Therefore, the aim of this project was to establish in vitro embryo production protocols to study differences between breeds and to improve embryo production outcomes. The first paper about ovarian characteristics and in vitro oocyte maturation in Norwegian Duroc and Landrace pigs was published in Veterinary Medicine and Science in May 2021 and showed differences in the number of follicles present at the ovaries and in oocyte maturation. A further study optimized the fertilization protocol, and was published in Zygote in April 2022. Fertilization was performed with different concentrations and cryopreserved sperm from three Duroc and Landrace boars. Promising embryo production results were obtained for both breeds during that experiment. The third article looked into differences in in vitro embryo development and results suggested that Duroc oocyte have a better developmental competence during in vitro embryo production. Furthermore, follicular fluid samples were analysed at the University of Copenhagen and steroid hormone profiles were different between the breeds. Further studies are recommended to optimize IVEP protocols per breed and to find out how differences between breeds are related to oocyte developmental competence and embryo quality. More data was collected and analysed regarding chromosomal abnormalities and their origin in embryos at different developmental stages. This last work was in collaboration with Topigs Norsvin and the University of Kent and an article is now being written.

Arbeidet i denne oppgaven har direkte praktisk relevans for Norsvin, da de etablerte protokollene og tilegnet kunnskap kan brukes videre i oppfølgingsstudier knyttet til in vitro embryo produksjon, embryokvalitet og embryo frysing. Dessuten er den tilegnete kunnskapen om embryohåndtering og kvalitet verdifull for fremtidig kommersialisering av embryooverføringer. Prosjektet har også økt nasjonalt og internasjonalt forskningssamarbeid med forskjellige universiteter.

Embryo transfer (ET) in swine has been used for commercial and breeding application. As a powerful breeding tool, ET can reduce the generation interval and increase selection intensity. Another advantage of embryo technology is the possibility to distribute genetics worldwide at significantly lower transportation costs and with better animal welfare than with the current practice of shipping live pigs. Application of embryo transfer in commercial pig breeding will have consequences for the breeding organizations. Collection and transfer of embryos with minimal-invasive techniques will enhance the efficiency and profitability of such an application and will be preferable from an animal welfare point of view. This may as well result in improved health status of pig populations when embryos instead of live animals are transported around the world. This are both important issues for acceptance of these procedures by the society. Main goal of this project is therefore to find a method to transfer embryos in an efficient and non-invasive way for improvement and animal welfare dissemination of genetics. This will be achieved through three different goals and activities: 1) Optimize the number of embryos obtained from a culled embryo donor by determining the ability to mature oocytes in vitro, learn about optimal physiological conditions in the sows, and suggest how to improve collection and maturation of oocytes. 2) Determine whether any genetic aspects of Estimated Breeding Values (EBV) TNB are expressed within the ovary and oocyte. Here we want to select oocyte donors based on breeding values, and incubate oocytes with follicular fluid from slaughter house based on contrast of EBVs in sows to optimize the oocyte maturation and survival. 3) In vivo collection of embryos for nonsurgical collection of embryos, which includes optimization of the flushing catheter.