Improvement of swine lineages for increased productivity, product quality, animal health and welfare

The core objective of this project is the establishment of consistent methods for the generation of genome-edited pigs, with enhanced capabilities for production efficiency and product quality, based on the manipulation of specific traits identified by Quebec’s pork industry. Using genome editing technologies based on the CRISPR-Cas9 system it is now possible to manipulate DNA sequences that control high value traits very precisely in a way that the result will be identical to mutations that occur randomly in nature. Consequently, this technology is envisioned to become a strategy for accelerated genetic improvement and increased productivity. The goal of this research is to create pigs with genome editions to reduce (or eliminate) the boar taint, i.e. the offensive odour or taste in the meat of non-castrated male pigs. Boar taint is currently prevented by piglet castration, which has important management and economic implications and represents an important animal welfare issue. We have identified a method to selectively decrease the production of androstenone (key responsible for boar taint) while maintaining the normal production of the sex steroids responsible for the improved feed efficiency and lean yield of intact male pigs, based on the introduction of specific sequence changes in key genes involved in androstenone synthesis (CYP17A1 and CYB5). The production of founder animals with the targeted genome editions is the more difficult aspect of the process and the one requiring most research efforts as, once established, the propagation of the animals with the edited-genome is conducted simply by breeding (e.g. artificial insemination). Multiple steps are required in the generation of genome-edited founders, and each of them will be a research subject in the general aim of developing proof-of-concept animals and consistent methodologies that will make the process highly repeatable for other genes that could be targeted in the future. Some of the methods optimized in the course of this research will have applications to conventional genetic improvement programs based on artificial insemination and embryo transfer. The steps subject of development/optimization under this research include: methods for transfer of the CRISPR-Cas9 tools to porcine oocytes/zygotes (injection vs. electroporation); developmental stage when the CRISPR-Cas9 tools are introduced (oocytes vs. zygotes); source of zygotes (fertilized in vivo vs. in vitro); modulation of DNA repair pathways, site (oviduct vs. uterus) and developmental stage (zygote, cleaved or blastocyst) for embryo transfer, and recipient females (self vs. foster embryo transfer). Developing an effective approach to reduce boar taint in non-castrated pigs would have an enormous impact on Quebec/Canada swine industry. This project represents a unique opportunity to attain this goal and develop new strategies to support sustainable animal production.