we rescued two puppies froma dumpster years ago. we were poor college students and it was tough to afford vet care for them. we delayed getting them spayed because we were careful to keep them inside and they were too young to go into heat at first. they both came into heat and i discovered that not only do they whine and beg to be let out to mate, they bleed like a human having her period. i have no desire at all to clean that up, or to enforce the wearing of special dog period panties. so they got spayed immediately and went on to live long, happy puppy free lives.