We began the avodah of korbanos in Mitzrayim, when we brought the sheep to slaughter as the Korban Pesach. Man was created on the same day as animals, but is distinguished as above them due to his Divine spark. When we act in a way that engages our Divine spirit, we are elevated above the animals and can slaughter them, both for korbanos and for our own use. Mitzrayim did not distinguish themselves as elevated humans, but rather ran their lives completely governed by desire. When we brought the Korban Pesach in the middle of Egypt, we demonstrated our elevated status over animals.