The horns of Buffalo, Yak and other bovine have also been used as options to rhino, both knowing and unknowingly. (As the number of rhino plummet, more counterfeit product are flooding the market.)
In the search for a more ethical replacement, there have been powders and elixirs advertised as "rhino horn alternatives"most of which essentially contain keratin (the main ingredient in rhino horn).
One recent group has a product they've touted as "biologically identical material" made of New Zealand sheep wool. Claiming health benefits from the concoction, the Vietnamese-Americans hope was to curb poaching and benefit rangers from the sale of their product. Rhinoceros Horn alternative