Australian racing chiefs have hailed a court ruling that found five trainers and three stablehands guilty of doping offences in a major scandal involving more than 100 races over several years.

In one of Australia's biggest horse-racing controversies, high-profile trainer Robert Smerdon was among those found guilty of an unprecedented 271 breaches of race-day rules between 2010-17.

Most of the offences related to dosing horses with a banned mixture of sodium bicarbonate, or baking soda, before top races, which helps reduce the build-up of lactic acid, allowing them to run for longer.

Racing Appeals and Disciplinary Board chairman Judge John Bowman said at a hearing in Melbourne's County Court on Tuesday that it was "probably the biggest scandal and the most widespread investigation in the history of Australian racing".

"This was a long-running systematic conspiracy to try and obtain an unfair advantage in well over a hundred races over seven years," it said.

"There has been dishonest, corrupt or fraudulent, improper or dishonourable actions of the highest order."

It found Smerdon and stablehand Greg Nelligan were the driving force behind the scam, with all those involved having links to the Aquanita Racing stable.

It followed a four-month investigation by Racing Victoria stewards.

Racing Victoria chief executive Giles Thompson said in a statement that it "sends a very strong signal to anyone who thinks they can undermine the integrity of the sport by actively breaching the rules of racing".

"It also is a ringing endorsement of the investigative work of our integrity services team who found these breaches and ran an exhaustive four-month investigation before laying charges against these eight people," he added.

"We are committed to ensuring that the very small minority who seek to breach the rules of racing and undermine our sport are found, investigated and ultimately prosecuted. That is what our participants, our customers and the wider public expect us to do."

Sentencing is expected on Thursday, with the main culprits facing life bans.