Another man also saw a herd of cows yesterday morning by the quarantine paddock just downstream of Red Bridge.
Hawke's Bay Regional Council chairman Rex Graham was equally disappointed.
"It is just tragic that farmers think they can still do it. I just wonder about what is in their brains when they carry on like this," Mr Graham said.
The council is working to put an end to this practise through a plan change but Mr Graham said this took time and he didn't expect it to be finalised until 2018.
"We are addressing the issue and this will be stopped eventually but, in the meantime, it is just sad people are ignoring the problem."
This change could mean all rivers and streams in the Tukituki catchment have to be fenced.
The issue caused a public outcry after the gastro outbreak in August when, although it wasn't the cause, the Tukituki was found to be filled with pollutants.
The river is a source of recharge for an aquifer which provides drinking water.
A more precautionary approach was wanted and councillor Tom Belford said earlier that photos of cows wading in the river provided a "vivid illustration" to where contaminants came from.
"Although they might not be the cause of the gastro outbreak, it signified an attitude toward what kind of protection was needed," Mr Belford said.
