Two livestock companies have been fined more than $70,000 each following a discharge of animal effluent into the Makino Stream.
PGG Wrightson and Carrfields Livestock appeared at the Environment Court in Levin on Monday.
The offending occurred at the Feilding stock yards, which is the largest stock yard in the southern hemisphere, in February last year.
Effluent had entered the stream through a storm water pipe connected back to the stockyards.
The discharge was brought to the attention of Horizons Regional Council by a member of the public.