The Apis bull. That was a bull with a certain marking on its head that signified divinity.
The holy bulls - not to be confused with...heh...Papal Bulls - lived a life of pampered luxury and were mummified after death.
That is...ALL the bulls were mummified, and preserved for history. Imagine how much space that must have taken up. When I lived in Alexandria, Egypt, I often visited the remains of the Serapeum temple complex. It had a huge underground space reserved for storing dead Apis bulls.
The Graeco-Roman Museum in Alexandria had something almost as neat as an Apis bull - a huge mummified crocodile, in honor of Sobek the crocodile god. The mummification of that thing was amazing. Thousands of years later, it still looked ready to take a bite out of any passing human.
I remember reading something about how the Greek/Macedonian Ptolemies must have reacted when they took over as "Pharoahs." That scam meant they had to go along with all the ancient Egyptian religious beliefs. Or pretend to, anyway.
The Pharoah's wife, among other things, was seen as the human embodiment of Hathor...the Great Cow. This meant the Ptolemaic women embodied (to their way of thinking, probably) a large, stupid farm animal who spent most of its time standing around in its own shit.