This Bible contradiction is from the Skeptic's Annotated Bible.
Yes, they were all killed.
Exodus 9:3-6 View context
Behold, the hand of the LORD is upon thy cattle which [is] in the field, upon the horses, upon the asses, upon the camels, upon the oxen, and upon the sheep: [there shall be] a very grievous murrain.
And the LORD shall sever between the cattle of Israel and the cattle of Egypt: and there shall nothing die of all [that is] the children's of Israel.
And the LORD appointed a set time, saying, To morrow the LORD shall do this thing in the land.
And the LORD did that thing on the morrow, and all the cattle of Egypt died: but of the cattle of the children of Israel died not one.
No he saved some to kill later.
Exodus 9:19 View context
Send therefore now, [and] gather thy cattle, and all that thou hast in the field; [for upon] every man and beast which shall be found in the field, and shall not be brought home, the hail shall come down upon them, and they shall die.
Exodus 12:29 View context
And it came to pass, that at midnight the LORD smote all the firstborn in the land of Egypt, from the firstborn of Pharaoh that sat on his throne unto the firstborn of the captive that [was] in the dungeon; and all the firstborn of cattle.