The court had previously heard that an investigation revealed Erasmus had broken the tails of 115 of his 135 cows over a period of three to four weeks.
Other cows had broken jaws.
He used steel pipes and the milking cups in the cow shed to hit the animals.
Mr Mikkelsen said 25 of the cows were in serious pain and distress, and had to be put down.
Some of the animals had broken legs, swollen hocks, weeping lesions, swollen joints and infections.
Auckland SPCA executive president Bob Kerridge congratulated the MPI for appealing against the sentence and was pleased to hear the Rotorua judge was prepared to send Erasmus to prison.
He said the crime sounded "horrendous" and urged members of the public to report animal cruelty on farms.