What is the ruling if the owner possesses an animal of greater value than the prescribed Zakat animal?

Primary text

If the owner possesses an animal of value greater than the prescribed Zakat share, it is preferable that he offers it voluntarily as an extra donation (*mutatawwi'an*) without obligation. If he does not offer it voluntarily, he is compelled to purchase the exact required Zakat animal using funds other than his Zakat-eligible wealth.