A move by Fonterra to improve water quality in lakes, rivers and streams has been welcomed by the Otago Regional Council and Environment Canterbury.
A new clause in the dairy co-operative's terms of conditions of supply requires farmer suppliers to keep stock out of waterways.
Farmers have 18 months from the beginning of next season to comply with the new condition of supply.
The move is in line with the outcome envisaged in the ORC's good water good farming rural water quality strategy.
"It is an excellent move and one we are right behind," chairman Stephen Woodhead said.
The ORC strategy was aimed at maintaining and improving water quality in the region's rivers, lakes and streams.
Improving water quality in natural waterways throughout Canterbury was one of the most important issues facing land and water users, as well as Environment Canterbury, ECan commissioner David Caygill said.
"The move by Fonterra will ensure we continue to make progress in improving water quality by restricting stock access to natural waterways."
It also strengthened the voluntary measures under the Clean Streams Accord signed eight years ago by Fonterra, regional councils, Ministry for the Environment, and the Ministry of Agriculture and Forestry.
In June, ECan introduced new rules to exclude stock from natural waterways in its Canterbury Natural Resources Regional Plan.
"Our simple message to farmers is they should be putting measures in place to ensure stock are kept out of natural waterways to safeguard and improve water quality," Mr Caygill said.
ECan is introducing additional rules in June 2012 which prohibit all intensively farmed stock from entering natural waterways in Canterbury.