In Tantric Buddhism, they learn to recite mantras, visualization and bardo delivery with all respect, before they eat the meat, the meat will be purify and spirits of the animals will be delievered to Heaven and remain the meat for human consume in order to obtain nutrition of human body.  We all know that even a glass of water has living organisms in it, millions of living organisms, bugs, insects, worms, caterpillar.. etc would be killed to obtain a intact vegetable for the vegetarian.