The Missiplicity Project, Genetic Savings & Clone and Sooam Biotech Research Foundation have all learned that dogs are almost certainly the hardest of all species to clone, for the following five reasons:

1) Poorly understood physiology. Until Missyplicity/GSC came along, there were no major commercial interests underwriting research on the reproductive physiology of dogs, resulting in a fundamental knowledge gap. By contrast, livestock and human reproduction have been studied extensively and are very well understood. After years of research by GSC and Sooam, we finally understand how to clone dogs. However, we still have work to do to understand these unique animals more fully.

2) Infrequent estrus. Virtually all mammals have regular and predictable estrus cycles (e.g., periods of fertility). These cycles generally range between 2-6 weeks. Dogs are unusual in that they only go into estrus once or twice a year at virtually random intervals. Only dogs in estrus can donate eggs for cloned embryo production or serve as embryo recipients. With infrequent and unpredictable estrus cycles, the timing of both creating and transferring the cloned embryos is very challenging.

3) Immature ova. The cloning process requires mature ova (e.g., eggs). The ova of most mammals reach maturity within the ovaries and are ready for fertilization (or use in cloning) at ovulation. The dog, however, ovulates immature ova that complete their maturation within the oviduct about 2-5 days post ovulation. It is extremely challenging to obtain these eggs from the oviduct at the precise time they are fully mature – a window of just a couple hours within a 6-12 month reproductive cycle.

4) Opaque ova. Virtually all mammalian ova are translucent so the inside of the ova can be seen and manipulated. Canine ova are permeated with thick, black lipids (fats). These black lipids are an energy source for the egg, but unfortunately it makes the eggs opaque and thus difficult to assess, enucleate, etc. We are developing safe imaging technologies that enabling visualizing the interior of canine ova without damaging them.

5) Animal welfare. Cloning livestock does not require welfare standards that are any higher than the prevailing standards of the food industry, which are frankly not that high. Dogs on the other hand are man’s best friend and must be treated as such throughout the cloning process. Only the highest veterinary and animal care protocols are acceptable. While we happily embrace this standard, there is also no question that it complicates the process of cloning dogs compared with other species.