Why does it say here "veha'Kerev veha'Kera'ayim"? Above (verse 8), it says "v''Kirbo u'Chra'ay"!
Moshav Zekenim citing R. Yehudah ha'Chasid: Tana d'Vei Eliyahu (6) says that an ox does not cross its legs when it walks, but a Seh does. Therefore, their digestion and excrement are different. 1
So explains Matanos Kehunah on Vayikra Rabah 2:12.
Why must one wash the feet and innards?
Hadar Zekenim: They go on the King's table; it must be honorable.