SOFREP has a good article about the necessity of live tissue training for medics. They use goats which PETA objects to:

Today, groups like PETA are engaging in political activism to try to shut down LTT in the SOCM school house at Ft. Bragg. This can’t happen. It will literally kill our soldiers. Groups like PETA have convinced certain politicians that the same quality training can be done on mannequins or medical training dummies. This simply is not true. There is nothing more realistic than living flesh and blood.