Andrew Hoggard, Federated Farmers Manawatu-Rangitikei provincial president, said Macdonald's actions were inexplicable.
"We genuinely thought crimes like this were committed by some low-life toe-rag who'd never worked a decent day in their life. It is a real shock to discover MacDonald has admitted to what are acts of sabotage.
"Frankly, I can't understand the rhyme or reason.
"As a farmer, Macdonald well knows there are codes of animal welfare on how we treat our stock. I have never heard anything untoward about how he treated his own stock, so how could he sneak onto another farmer's property to kill their calves?
"MacDonald also knows how hard it is to produce quality milk. Milk the lifeblood of any dairy farm and I cannot understand why anyone would maliciously and callously empty a vat.
"These are cold and calculating actions."
Mr Hoggard said Macdonald's actions showed he was not fit to farm.
"Farms absolutely turn on trust. Since it has been reported MacDonald has admitted to these crimes, how could you put your undivided trust in him? Speaking personally, I couldn't."
Macdonald was found not guilty of murdering his brother-in-law Scott Guy last month after a month-long trial.
During the trial a four hour interview Macdonald gave two detectives was played to the court where he confirmed other acts of arson and vandalism -directed at Scott and Kylee Guy - but insisted he was not responsible for the murder.
He told the officers he was "not that extreme" that he would take someone's life. "It looks obvious, these leading up to events, but I'm not that blimmin psycho."
The judge that sentenced Boe said he "readily admitted" his actions when police investigating the murder of Scott Guy visited him in his new home of Queenstown, in April 2011.
Boe's confessions provided police with the crucial breakthrough they were hoping for and they arrested Macdonald for murder soon after.
They alleged he killed Mr Guy as a rivalry over the family farm - but he has always maintained his innocence.
Court documents viewed by the Herald , show Boe went along with Macdonald who he viewed "as a leader" and was under the influence of him.
The crimes took place in August 2007, soon after Macdonald and Boe were caught poaching on Graham Sexton's Foxton farm. When they were caught by the neighbour, Paul Barber, who phoned police, Macdonald tried to claim he was only "photographing deer". He later apologised for his actions at a meeting at Mr Sexton's home and he returned a number of stag heads of animals he'd shot on the property.
But seven months after the calves were killed and the milk vat sabotage, he and Boe returned to Mr Sexton's farm and burned the whare down.
It had no electrical connection and was used mainly as a sleep out and by duck shooters and was found smouldering on March 22, 2008.
Macdonald's wife Anna, who is Mr Guy's sister, gave evidence during the trial that her husband's relationship with Boe was an immature one, and she was unaware of what they were doing on their regular night "missions".
During Macdonald's trial his lawyer Greg King - speaking of the acts against the Guy's - said his client had admitted some heinous things and would be punished, but that did not mean he was a murderer.
The suppression order was supposed to be lifted when Macdonald appeared in the Palmerston North District Court for a callover on Tuesday, but were continued by the district court judge who declined jurisdiction to sentence Macdonald.
He will now be sentenced by the High Court later this year - a sentencing date will likely be set when he next appears in court on September 14.
- HERALD ONLINE
