“Why do cows have hooves instead of feet?”/“Because they lactose.”

“Lactose” sounds like “lack toes,” prompting the pun:
 
Q: Why do cows have hooves instead of feet?
A: Because they lactose.
 
“Why do cows have hooves? Because they lactose” was cited on Twitter on September 28, 2011. The pun went viral on Twitter in August 2014.
 
   
Wikipedia: Lactose
Lactose is a disaccharide sugar derived from galactose and glucose that is found in milk. Lactose makes up around 2–8% of milk (by weight), although the amount varies among species and individuals, and milk with a reduced amount of lactose also exists. It is extracted from sweet or sour whey. The name comes from lac (gen. lactis), the Latin word for milk, plus the -ose ending used to name sugars.
 
Twitter
Joe H
‏@iddeidus
Q - Why are dairy cows crappy at football? A - Because they lactose! #deadlineday
1:51 PM - 31 Aug 2011
 
Twitter
Stacy’s Mom
‏@Maddie_Eggert
@semi_french “Why do cows have hooves? Because they lactose.” -Coach E #laughedsohard
3:01 PM - 28 Sep 2011
 
Twitter
Tim
‏@timwellslive
Why do cows have hooves? Because they lack toes. #timwellsoriginals
9:20 PM - 11 Jan 2012
 
Twitter
Gareth Jones
‏@gareth_danger
Cows get tipped over easily because they lactose.
12:22 PM - 10 Apr 2012
 
Twitter
Stephen Long
‏@UABStephenLong
Why are cows feet called hooves? Because they lactose!
9:21 PM - 1 Aug 2014
 
Twitter
Lesha XO
‏@my_pet_fairy
quickbewitty: quickbewitty: Why do cows have hooves instead of feet? Because they lactose http://tmblr.co/ZmYB0w1PEqe2x
4:23 AM - 26 Aug 2014
 
reddit
Why do cows have hooves instead of feet? (self.Jokes)
submitted March 27, 2015 by shitwhenyoucan
Because they…. lactose…..
 
reddit
Why do cows have hooves instead of feet? Because they lactose (self.Jokes)
submitted November 29, 2015 by Lewisjb92