Is anybody else wondering why Zeus decides to turn Io into a cow to hide her from Hera? Like, he has the power to turn her into anything he wants—a flower, a butterfly, a candy bar wrapper. So why out of all the things in the universe, a lot of which would've been much less conspicuous, does he choose to transform his hot, young lover into a big, white heifer?
To make sense of it, we did a little digging on the symbolism of cows in general. Turns out, cows were pretty important symbols in lots of ancient religions (and are still sacred to Hindus today). Tons of ancient societies were totally dependent on cattle; the bovines helped plow the fields, provided meat and dairy products, and their poop was great for fertilizer and making fires with (stinky fires, but whatevs). Given all this, it's no wonder ancient people started thinking of bovines as totally divine.
More specifically, cows were often the symbols and sacred animals of mother goddesses like—wait for it—Hera. Ding, ding, ding! Oh, this is totally starting to make sense. So Zeus turns Io into a heifer to try to appease Hera with an animal that's sacred to and symbolic of her. It also makes sense on a larger symbolic level, since Io was a bit of a mother goddess herself, who according to some was associated with big time Egyptian goddess, Isis.