Moses insisted that Israel's livestock go too, saying that not even what would be left behind?

Answer: A hoof

"Even our livestock must go with us; not a hoof will be left behind," Moses told Pharaoh after the plague of darkness.

“Even our livestock must go with us; not a hoof will be left behind, for we will need some of them to worship the LORD our God, and we will not know how we are to worship the LORD until we arrive.””— Exodus 10:26 (BSB)