Peter Moody has vowed to never again have a large string of horses should he make a return to training.

Moody, the trainer of champion mare Black Caviar, will shut down his training operation on Thursday night as he begins a six-month cobalt suspension.

"I will never be a large public trainer again," Moody said, confirming he is stepping away from training.

"I would never want to put myself through having three hundred horses and fifty or sixty staff and a thousand clients again.

"Would I look at something a little more private, or intimate, with a small group of clients, or a private job in the future? That would be a remote possibility."

Moody and his wife Sarah made a decision on Saturday to wind up their training business.

After he learnt of his cobalt penalty on Thursday, it was Moody's intention to engage David Brideoake as an interim trainer.

But after talking to family, management and close confidantes, Moody realised the Brideoake appointment wasn't workable.

Since he was charged in January last year, Moody said the saga had been financially and mentally draining.

And he said his results during the past six months had reflected his frustrations.

"Last season I ran second to Darren Weir in the premiership, this year I would probably run twenty-second," he said.

"It's not a fear of failure (that I walk away), it's a fear of not doing my job properly."

He said being found not guilty of administering cobalt to affect performance had made his decision to quit much easier.

Moody can could count on one hand the number of horses that had left his stable during the cobalt saga, but he has been unable to attract new business while the quality of his bloodstock had slipped.

"Eighteen months ago we had eighteen or twenty horses heading off to autumn and winter carnivals in Sydney and Brisbane," he said.

"This week I would struggle to fill the truck up," he said.

And Moody is also looking to sell out of the 70 horses that he and his wife share ownership.

"My wife and I have invested heavily in the industry, rightly or wrongly," he said.

"Maybe we should have made more investments outside of it.

"What we can get out of it in the next few months will determine our quality of lifestyle.

"It's an extremely expensive exercise employing lawyers, barristers and solicitors and the reason we did that we believed we did no wrong.

"At the end of the day it cost us a lot of money to be proved not to be a cheat."