In animal cloning, an ovum is collected by an animal and processed to form an embryo after fusion, which is going to be inserted to a surrogate mother. So my question is that why can't the embryo be inserted the animal that gives the ovum as they are both maternal?
It would make the result at least a little ambiguous. How would you establish with high confidence that the offspring was the results of your implanted cloned ovum and not a naturally fertilized one? DNA testing would have to be quite extensive to establish that offspring was a clone and not the result of an ordinary pregnancy. If you use a surrogate mother, the offspring will have DNA quite distinct from the surrogate.