Farmer Jozef Andrezejk claims their songs have boosted his herd's yield by litres each day.
Jozef says the animals stopped fidgeting during John and Edward's rendition of We Will Rock You.
And now he regularly plays the twins' tunes at his farm in Beaminster, Dorset.
'When our cows are happy, so are we,' Jozef tells The Sun.
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