The vast majority of mozzarella in the U.S. is produced from cow's milk and is accurately identified as mozzarella cheese. By tradition, cheese is made from milk. Leprino uses only Grade A milk from cows. So, the answer depends on to what degree you are a vegetarian. These products are not used.
Most authorities consider that cheese was first made in the Middle East.
The earliest type was a form of sour milk which came into being when it was discovered that domesticated animals could be milked. He is said to have filled a saddlebag with milk to sustain him on a journey across the desert by horse. After several hours riding he stopped to quench his thirst, only to find that the milk had separated into a pale watery liquid and solid white lumps. Because the saddlebag, which was made from the stomach of a young animal, contained a coagulating enzyme known as rennin, the combination of the rennin, the hot sun and the galloping motions of the horse had effectively separated the milk into curds and whey. The nomad, unconcerned with technical details, found the whey drinkable and the curds edible.