The trick is to view the human body as nothing more than meat. Is it really that different from a pig in a butcher shop window? Same skin tone, same colour blood, same entrails and bones and fat. I saw a Syrian rebel slice open a human torso, pull out what looked like his liver and take a big bite. Truthfully, it was no different to seeing a slaughterman eviscerate and quarter a hog.
Likewise, I have seen images of a suspected South American pedophile after he was decapitated, just cold meat and nothing more. The truly sad thing was that they didn't find the right fence post to fix the head to. It was too wide, it didn't sit right. Just because it ends in a point doesn't mean it's sufficient to pike a head on.
Point is, they're nothing, they're just animals being slaughtered, nothing more. They shake and cry and grow still and then it's over. My advice is to see footage of a slaughterhouse at work, watch the mechanics of death. It really isn't dissimilar to what happens when one human kills another.
This post gave me the chills, you're basically saying having a disregard for human life. Desensitising yourself is dangerous, it can blur the line between right and wrong, it sets a very dangerous precedent. And unless you're planning to become an assassin or a serial killer anytime soon it's the last route you want to take. Humans aren't pigs up for slaughter, never draw that comparison. Instead try to relativise it to things that makes sense for you personally.