Anthony Brolly, 34, has been sentenced in Taupō District Court on seven charges in a case brought by the Ministry for Primary Industries.
He was fined $12,000 and ordered to pay $5292 vet costs.
Brolly failed to feed, adequately treat and prevent parasites in 245 calves, and ill-treated five calves.
Animal Welfare regional manager Brendon Mikkelsen said it was serious offending and all cases of animal abuse were unacceptable.
"The animals were Mr Brolly's primary responsibility and he failed them. He failed to provide proper and sufficient food for a long period. He knew he should have treated the animals for parasites, but he didn't."
An animal welfare inspector visited Brolly's 55ha leased property at Tīrau on May 20, 2020, after a complaint from a member of the public.
The inspector found the majority of Brolly's calves in a paddock in an emaciated condition. One calf had died and was seized for examination. The post-mortem showed it had died after an extended period of malnutrition.
On May 21, 2020, an animal welfare inspector and a veterinarian returned to the property. They found another recently deceased calf and three calves stuck in a bog at the end of the paddock.
Large amounts of parasitic worms were found to be present in a sample of calves.
The vet said the scale of the issue on Brolly's farm was of a magnitude and severity he had never seen before in his 25 years of experience.
Mikkelsen said without the intervention of animal welfare officers the calves stuck in mud would have died within the following 24 to 48 hours.
"In New Zealand, everyone must take responsibility for animal welfare. We strongly encourage any member of the public who is aware of animal ill-treatment or cruelty to report it to the MPI animal welfare complaints freephone 0800 00 83 33."