Who knows what makes a cow 'happy' anyway?
My old man had a dairy of approx. 100 +_ cows.
We milked approx. 65 head on average year around.
We had a radio in the barn that we listened to and the cows apparently liked that too, as when the radio died and was not replaced for 2-3 weeks, milk production dropped noticeably!
We also had a hydroponics system in place in the late 50's and the cows loved the green oats that came out of that so much that when that unit was down because of mold and a needed cleanup we actually had to force the cows out to pasture.
One other item about cows and music - there was/is? a
video about a small group of musicians who drove out near a pasture full of cows, set up their instruments along a side-ditch
fence, and started playing. Most of the cows ambled over to listen to the classical music being played. Happy cows - or just curious cows?