It is believed the animals had been there for between a few days to six months.
The remaining live sheep had daggy rear-ends and faecal samples which indicated some sheep could be heavily infested with worms.
Ms Coxhead was ordered to get the sheep assessed by a vet and was given seven days to comply.
On re-inspection the animal welfare officers discovered a freshly dead sheep and found no action had been taken by the farmer as the 30 sheep were still in the same condition as the initial visit.
Faecal samples were taken from the freshly dead sheep and from three of the live sheep.
Tests confirmed the dead sheep and one of the live sheep were infested with worms.
Ministry for Primary Industries manager of compliance for the Northern region, Brendon Mikkelsen, said an egg count of 500 is deemed to be significant, meaning the animal would require treatment.
The dead sheep that was tested had an egg count of 25,500.
Mr Mikkelsen says the property was again visited and a further 31 dead sheep were found, a ewe and lamb were also euthanised at the recommendation of the visiting vet.
"This farmer had previously come to our attention for failing to treat her sheep against fly-strike.
"She was reminded of her responsibilities to ensure that the physical health and behavioural needs of her sheep were met. The latest incidents are therefore very disappointing."
Mr Mikkelsen says people who care for farm animals had a legal responsibility to ensure their animals do not suffer.
"The animals in this case clearly suffered, some for long periods of time.
"Neglecting animals and failing to treat them can also have serious consequences for the wider agricultural industry, and, if widespread, would make New Zealand's animal products far less desirable internationally," he says.
Mr Mikkelsen says he hoped this conviction and sentencing reminded farmers to ensure all animals in their care received appropriate treatment which alleviates any unreasonable or unnecessary pain and distress.
