The offending was discovered when an MPI animal welfare officer, acting on a complaint, visited a Pongaroa grazing block managed by the pair in October 2012.
The officer found lactating and pregnant cows in very poor condition with limited feed.
A veterinarian told MPI the property was "grossly overstocked" and there had been "severe and prolonged underfeeding". The veterinarian said animals do not get into this position overnight and such a level of underfeeding put them in severe risk of death.
The cows were gradually brought back to acceptable health.
Ministry officers had visited the property previously on similar complaints and had worked on mitigating animal welfare issues.
Officers formally warned Ms Hayward in 2010 that further animal welfare offending would likely result in a prosecution.
Judge Stephanie Edwards said significant ill health was a mitigating factor in setting the limit of the fine for Mr Matthews, and Ms Hayward's fine was reduced for mitigating personal factors.
The maximum penalty for failing to meet the needs of stock is a fine up to $50,000 and/or one year in prison.