The arrested individual, identified as Venkatesh, 22, is a resident of Davanagere, the police said.
He had been caught red-handed while having sexual assault on a cow, at Singapura Layout in Bengaluru.
The police said Muni Hanumantappa who kept five cows and six calves at his cow-shed had caught Venkatesh in the act, and reported the the matter to the police.
His act was initially observed by the neighbours, who informed Hanumantappa.
Later, Hanumantappa went to the cow-shed and hid himself to catch Venkatesh, who eventually came there, stripped and indulged in unnatural sex with a cow.
The police said that further investigation into the matter is underway.