I wrote about this a while back:
http://sugarmtnfarm.com/tainted-big-pharma/
I recommend not using it. If you do use it be very, very, very careful not to stick yourself with the 'castration vaccine' or you can end up sterilized as has been documented in Europe and by the maker of the drug. In addition to being another expense and additive to your food it is dangerous.
Far better is to simply breed, feed and manage away from taint. See:
http://www.google.com/search?q=site:sugarmtnfarm.com+taint
Cheers,
-Walter Jeffries
Sugar Mountain Farm
Pastured Pigs, Sheep & Kids
in the mountains of Vermont
Read about our on-farm butcher shop project:
http://SugarMtnFarm.com/butchershop