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

加拿大在家畜遗传学方面，特别是在奶牛和猪方面，已成为世界领先的国家。然而，全球食品市场的持续变化要求除生产性状外，其他性状，如营养成分、产品质量、动物健康和福利，成为牲畜选择计划的优先目标。基因组编辑技术被认为是帮助开发更可持续的动物生产系统的有力工具，因为它能够快速调节动物所需谱系的特征，这是通过传统育种方法难以或不可能实现的。利用基于CRISPR-Cas9系统的基因组编辑技术，现在可以非常精确地操纵控制高价值性状的DNA序列，其结果将与自然界随机发生的突变相同。在养猪生产中，阉割仔猪是必要的，以避免公猪污染，即来自未阉割猪的肉产生的令人不快的气味和味道，但这是动物福利的一个重要问题，具有重要的伦理、管理和经济意义。因此，迫切需要开发工具和策略来满足消费者的要求和有关仔猪阉割的新法规。本研究计划旨在开发一种替代阉割仔猪的方法来预防公猪感染。这将通过替代雄烯酮合成酶CYP17A1和CYB5中的两个氨基酸，选择性地减少雄烯酮（公猪污染的关键因素）的产生来实现。根据先前的研究，预计这将减少公猪的粪便，同时保持其他性类固醇的正常生产，从而提高完整雄性猪的饲料效率和瘦肉产量。这将对加拿大养猪业和经济产生巨大影响。

Canada has become a world leader in livestock genetics, especially in dairy cattle and swine. However, ongoing changes in the global food market require that other traits, in addition to production traits, such as nutrient composition, product quality, animal health and welfare to be priority objectives in livestock selection programs. Genome-editing technology is envisioned as powerful tool to help developing more sustainable animal production systems since it enables a quick modulation of traits in a desired lineage of animals, which would be difficult or impossible to achieve via traditional breeding approaches. 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. In swine production, piglet castration is necessary to avoid boar taint, i.e., the unpleasant odor and flavor emanating from meat originating from non-castrated pigs, but it represents an important issue for animal welfare and has important ethical, management and economic implications. Therefore, there is an urgent need to develop tools and strategies to address requirements from consumers and new regulations regarding piglet castration. This research proposal has been prepared to develop an alternative to piglet castration for preventing boar taint. This will be achieved by selectively decreasing the production of androstenone (a key factor for boar taint), by substituting two amino acids in the androstenone synthesis enzymes CYP17A1 and CYB5. Based on previous studies, this is anticipated to reduce boar taint while maintaining the normal production of other sex steroids responsible for the improved feed efficiency and lean yield of intact male pigs. This would have an enormous impact on the Canadian swine industry and economy.