“What kind of milk do they use to make Swiss cheese?”/“Hole milk.”

A riddle about the holes in Swiss cheese is:
 
Q: What kind of milk do they use to make Swiss cheese?
A: Hole milk.
   
The pun is on “whole milk.” “Is Swiss cheese made out of hole milk?” was posted on the newsgroup comp.sys.mac.advocacy on January 12, 2008. “What kind of milk do they use to make Swiss cheese? HOLE milk. Get it?! #reasonswhyimsingle” was posted on Twitter on October 3, 2011.
 
“How do you make Swiss cheese?”/“With a holey cow” is a similar Swiss cheese riddle.
 
     
Wikipedia: Swiss cheese
Swiss cheese is a generic name in North America for several related varieties of cheese, mainly of North American manufacture, which resemble Emmental cheese, a yellow, medium-hard cheese that originated in the area around Emmental, in Switzerland. Some types of Swiss cheese have a distinctive appearance, as the blocks of the cheese are riddled with holes known as “eyes”. Swiss cheese without eyes is known as “blind”. (The term is applied to cheeses of this style made outside Switzerland, such as Jarlsberg cheese, which originates in Norway).
     
Google Groups: comp.sys.mac.advocacy
Apple and Adobe announcement
Snit
1/12/08
(...)
Is Swiss cheese made out of hole milk?
 
Twitter
Red Swans At Night‏
@bigswedeE30
When they make swiss cheese do they use hole milk?
11:18 AM - 6 Nov 2009
 
Twitter
Katie Zwick‏
@katiezwick
What kind of milk do they use to make Swiss cheese? HOLE milk. Get it?! #reasonswhyimsingle
7:39 AM - 3 Oct 2011
 
Twitter
Jessica‏
@JessBeautiful
What kind of milk is used to make swiss cheese? Hole milk. hahaha Have a fabulous day, all! <3

6:31 AM - 3 Feb 2012
       
Reddit—ShittyAskScience
Is Swiss cheese made from whole milk? (self.shittyaskscience)
submitted April 13, 2014 by whale_shoes
COMMENTS
ConnorCs50[🍰}
No, it’s made from hole milk hence the holes.
 
Reddit—Dad Jokes
How do you make swiss cheese? (self.dadjokes)
submitted December 4, 2016 by ProWaterboarder
With hole milk
 
Reddit—Dad Jokes
What kind of milk do they use to make swiss cheese? (self.dadjokes)
submitted January 29, 2018 by uldrenek
Hole milk.