Precision Animal Breeding to Make Genetically Castrated Animals for Improved Animal Welfare and Alternative Breeding Applications

The main purposes of surgical castration are to reduce aggressive behaviour of males and remove 'boar taint' from pork. Because of issues related to animal welfare, European swine industry leaders voluntarily signed a declaration to abandon all forms of surgical castration by Jan., 2018. Alternatives, like vaccinations against boar taint or marker selection against taint, possibly have negative effects on carcass yield and libido, respectively.  As an alternative, we report the efficacy of precision cross-breeding, also known as gene-editing, as a means for elimination of surgical castration. A single edited cell line (KISSR -/-) derived from a White Composite male pig was used for SCNT. All porcine cloning of TALen edited gene knock-out cell lines was done at Minitube of America. Blastocysts were transferred into three recipients, which resulted in two successful pregnancies yielding 19 piglets (2 still birth). The 17 remaining animals were raised to 200-225 lbs. The KISSR KO edit was diagnostically confirmed as was lack of testicular development. The animals looked and acted (low aggression) like barrows in good health, and were phenocopies of humans with hypogonadotropic hypogonadism. We attempted to initiate testicular development in these pigs using hormone therapy as a potential method to rescue reproductive competency and/or check for their integrity as potential recipients for germ cell line transfer. Puberty induction studies were set up with three groups of KISSR KO cloned male pigs (each N=4): 1) control/sham injected, 2) FSH/slow release treatment and 3) GnRH treatment. The GnRH protocol was not expected to induce puberty; but testosterone, LH, and FSH levels could be determined, to support future testing of hormone treatments. All animals were euthanized humanely for subsequent histology and gene expression studies. The hormone treated testes increased mass and structural histology strongly supported the potential for recovery of sperm production with a more efficacious treatment even though sperm were not detected in any group. Current studies are underway to compare growth efficiencies between normal, castrated, and KISSR KO pigs. These results are needed to validate the market value of genetic castration. We also are testing alternaitve gene knock-outs to maintain testicle development without germ cell development. Overall, we demonstrated genome editing can be used to benefit animal welfare by eliminating stressful management practices in a single generation; and the potential to propagate these lines is possible through hormone therapy.