(WBND/CNN) - Some Indiana cows have something most other cows don't.
They all sleep on waterbeds.
Farmer Kalvin Imhoff of Sunnyview Farms says he put the waterbeds in back in 2005 for a simple reason: They make the cows happy, and happy cows equals more milk.
Imhoff got such good results that expanded his business. He's sold more than 4,000 similar waterbeds in Indiana in the past five years.
About 12 other farmers in his area now have their cows sleeping on waterbeds too.