we reached a conclusion in this thread ?☺One word: DNA..............Human and dog DNA is not compatible, it just is not. That's it..
1.someone got here and explained to me that if the DNA is too different then it cant unlock the egg barriers
2. obviously some animals have similar DNA and create a sterile offspring like horse and donkey
3. we agreed that atleast dog sperm can act as something that "interupts" humans sperm if a woman has sex with a man later, so it doesnt stop insemination, just reduces chance (by how much i have no idea)