“What does a cannibalistic cow eat?”/“Can o bull.”

“Cannibal” sounds like “can o’ bull.” “Can O’ Bull Chief” was a short movie feature in 1928.
 
A riddle was posted on Reddit—3amjokes on January 21, 2018:
 
Q: What does a cannibalistic cow eat?
A: Can o bull.
   
             
16 November 1928, The State-Times (Baton Rouge, LA), pg. 18-A, col. 7 ad:
People Theatre
(...)
Added—Comedy, “Can O’ Bull Chief”
 
Google Groups: comp.ai.philosophy
The missing link—CANTOP arguing now
Vivian Waugh
8/2/97
(...)
Meat my own Suture Self!  Auto-Braind; Can O Bull stew.
 
Google Groups: alt.humor.puns
Kids Puns of the Weak 11-02-04
Stan Kegel
11/2/04
(...)
If Spam were made of Beef could it be considered a “Can-O-Bull”? (Brad Williams)
 
Twitter
sydney werner‏
@hii_sydney
Can-o-bull
1:50 AM - 24 Jun 2013
     
Twitter
Not Your Dad‏
@CarriePoppyYES
My 5th grade teacher told me about the Donner Party, but I thought it was all a can o’ bull.
2:54 AM - 4 Sep 2013
 
Twitter
valeria‏
@ratleria
cannibal or can-o-bull?
7:52 PM - 22 Jan 2014
 
Reddit—3amjokes
What does a cannibalistic cow eat? self.3amjokes
Submitted January 21, 2018 by KryFuZe
Can o bull.
 
Twitter
3AM‏
@3AM_Jokes
What does a cannibalistic cow eat?... Can o bull.
5:22 PM - 21 Jan 2018