A herd of dairy cattle from Corrections Canada's Riverbend Institution were auctioned off Wednesday. (CBC)

The sale of 120 dairy cattle from a Saskatchewan prison farm is being slammed by the National Farmers Union.

The animals were sold at an auction held in Saskatoon on Wednesday. The 120 head of dairy cows came from a farm operation at the minimum security Riverbend Institution, a federal prison near Prince Albert, Sask.

The federal government has been phasing out prison farms on the argument that not enough inmates are finding agricultural jobs to justify the program. There are six such farms across the country, including the Riverbend operation, which began in the 1960s.

The NFU has launched a campaign to halt the closures.

"We're losing a major source of rehabilitation for people at Riverbend," said Kevin Wipf, executive director of the NFU. "The community's losing a source of agriculture that's local and contributing to the community. So we see it as a big loss, actually."

The Riverbend farm provided food as well as training in different agricultural jobs to inmates.

The NFU has been organizing rallies to bring attention to the closing of the farms.

In a news release issued Wednesday, the group said a meeting had been set for July 9 with a senior official from the Correctional Service of Canada to discuss the issue.

As well, the NFU said that a regional official with the CSC promised that livestock on a farm at the Frontenac Institution in Ontario would not leave there before that meeting took place.

The Frontenac operation is associated with the Kingston federal prison.

The NFU is one of six groups lobbying to stop the closure of prison farms.

In Kingston, they have organized a volunteer vigil to monitor activities at the Frontenac farm. They call it the Citizens On Watch Station, or COWS.