The taste of dog semen has been described as metallic, like the taste of blood, nails, sucking on a penny, or sticking a 9v battery to the tongue. There may be a woodsy or slight smokey note to it. Not all dogs have a metallic taste to them, and the strength of the metallicness reportedly does not vary based on diet or breed or state of intactness, but on individual.
The metallic taste may be caused by a non-essential component of the semen, such as a musk that dogs smell but humans perceive only as a taste.