I really like this idea.
African game reserve poisons horns to prevent poaching
If the whole reason for taking a rhino's horn (and mercilessly butchering the poor beast in the process) is for the inclusion of crushed rhino horn in 'traditional' Chinese medicine, then what better way to discourage this than by making that particular ingredient DEADLY?
In fact, why did no-one think of this before?
What greater dis-incentive can there be for including rhino-horn in some potion or other than the fact that, once you swallow, you begin to have stomach cramps, sweats, uncontrollable flatulence followed by explosive bowel evacuation, vomiting so violent that you bring up your own innards, muscle cramps so severe they crack bones, bleeding from every orifice, blindness, a sudden craving for the music of Bros followed, mercifully, by the passing of the craving for the music of Bros, abrupt brain expansion until the skull cracks, impotence, cracked nipples and then, finally, the unexplainable loss of all bank savings and death.
And, better still, there's stuff in the injected material which means it shows up on airport x-ray machines (I suspect that will be some metal then) - there's even a rumour that the stuff injected can actually be detected by Mr McCormick's 'bomb detector' (though I somehow doubt that!).