A police video interview with Macdonald, conducted at the Palmerston North police station last April 7 - the day he was arrested - is being shown to the jury at his murder trial this afternoon.
It is the first time the jury has heard Macdonald speak since he pleaded not guilty at the start of his trial almost a fortnight ago.
In the interview, Detective Laurie Howell questioned Macdonald on the arson of an old house that was due to be shifted off the Guys' property.
Macdonald, dressed in a green sweater and collared shirt, said the first he heard of the arson was from Mr Guy's father Bryan.
Asked if he was responsible for the arson, Macdonald shook his head and said: "No, no."
He said he did not know who had done it.
"It has no benefit to me whatsoever, it just creates more problems."
Mr Howell also asked Macdonald if he had any knowledge of the theft of two deer.
Macdonald said he read about in the newspaper but did not have any personal involvement in the matter.
"I'm not that stupid ... it's too close to home."
The Crown case is that Macdonald shot two deer from the Hocken farm and then buried them. He admitted the theft after a young accomplice, Callum Boe, confessed.
Macdonald told Mr Jackson of how he tried to make more effort to communicate with Mr Guy and spend more time with him and Kylee.
He accepted there were some tensions with Scott Guy but said those had been cleared up.
Macdonald said as a son-in-law he tried to "keep my head down" and did not demand a lot.
Throughout the interview he leaned against the table, crossed his arms or leaned back in his chair while talking to police.
The video screening is continuing.
Mr Howell earlier gave evidence that Macdonald was preparing his breakfast when he and colleague Detective Glen Jackson went to Macdonald's house to ask him to accompany them to the station last April 7.
"He quickly completed his bowl of Weet-Bix and got into the police car with me."
Mr Howell read Macdonald his rights in the car on the way to the station.
"He said that it made him a bit nervous at the completion of me telling him that."
The court earlier heard Macdonald told police he did not recognise the handwriting of graffiti he later admitted to painting on Mr Guy's house while it was being constructed.
Mr Jackson told the court he asked Macdonald if he recognised the handwriting of the graffiti, which included messages like "bitch slapper".
Macdonald replied he did not.
The men also discussed how the graffiti was made, with Macdonald asking: "So it was a brush used, not spray paint?"
Mr Jackson confirmed to him a brush had been used.
Mr Jackson also read aloud a transcript of an interview in which Macdonald spoke about a dairy conference in Invercargill he attended with Mr Guy between June 21 to 23, 2010.
Macdonald told police that he and Mr Guy went to different sessions at the conference so the men could get the most out of it.
"Scott and I were on the same page about the farm,'' he said.
The men agreed to get new milking technology to cut down on labour costs.
Macdonald said after they arrived in Invercargill, the motelier of the Moana Court lent the men a car so they could get some KFC for dinner.
Each night after the conference the men back went to the motel, got takeaways for dinner and watched Sky TV, which Macdonald said he was surprised to find in the motel.
On one night the men attended a dinner at a hotel, where they chatted to other farmers and saw a band.
Macdonald did not drink, which he had not done since his stag night, when Mr Guy got him "really drunk''.
The court last week heard evidence of tensions and competitiveness between Macdonald and Mr Guy.
Trial enters third week
The trial entered its third week this morning with evidence on the family farm's finances.
Dairy farming consultant David Beca, who now manages a farming company in Uruguay, facilitated a meeting with the Guys over the future of the farm in 2006.
Mr Beca said Macdonald was "highly involved'' in the dairy operation while Mr Guy was involved in the "support'' part of the business, which involved cropping and grazing to provide feed for the stock.
Mr Beca said the dairy operation was the "heart'' of the business and Mr Guy's role was "very much secondary to the core part of the business''.
He spoke with the couples - parents Bryan and Jo Guy, Scott and Kylee Guy, and Ewen and Anna Macdonald - about their hopes and fears for the farm.
"Scott and Kylee amongst other things were keen to take a more active role, Scott in particular, in the management and running of the business,'' Mr Beca said.
"Communication was mentioned as an issue or a problem that they felt needed to improve.''
Mr Guy expressed concerns that responsibilities were not clear and there were "too many bosses''.
The farm was not consistently profitable year after year and Mr Guy wanted more consistency.
"Scott specifically mentioned not wanting to disappoint his father.''
He was also concerned about competition with Macdonald.
Mr Beca said Macdonald wanted to have more family time, better accommodation and to ensure there was enough income to provide for his children's education.
He also had fears over what would happen if someone wanted to exit the business.
Mr Beca said the time involved in the dairy side of the operation was more intensive than the cropping operation, which Macdonald and his wife expressed concerns about.
Mr Beca said Bryan Guy was keen for the business to expand and for the next generation to be involved but was concerned that family relationships were sustained.
There were also questions over whether the business could provide for everyone in the family.
Giving evidence for the third time today, Bryan Guy said Scott's wife Kylee did not return to her home and moved back to Hawkes Bay the week after Scott died. The house was sold in July 2011.
He described how he and wife Jo helped the younger couples - Scott and Kylee Guy, and Ewen and Anna Macdonald - become 10 per cent shareholders in the farm and buy properties,
After Scott's death, Macdonald got an increase in salary of about $10,000 or more which "reflected the increase in responsibility he had''.
The trial continues this afternoon with a police video interview with Macdonald.
