Horses moving yards a fortnight ahead of the 2021 Cheltenham Festival could have a "massive impact" in terms of their diet, Paul Nicholls has suggested.
The 11-time champion trainer was giving his insight into the routines of horses, after Cheveley Park Stud sent eight trained by Gordon Elliott to other stables.
They made their decision after Elliott was prevented from having runners in Britain while a picture of him sitting on a dead horse is investigated by racing chiefs.
Unbeaten novice chaser Envoi Allen is the most high-profile horse making the switch – and will be prepared for Cheltenham by Henry de Bromhead.
Sir Gerhard, a leading contender for the Weatherbys Champion Bumper, is now in the care of Willie Mullins.
Nicholls received a selection of Jared Sullivan-owned horses from the latter trainer, including Laurina, last year.
The Ditcheat handler said often it is not straightforward taking over another yard's horses, as routines can vary a lot.
"It wouldn't be ideal for horse or trainer," Nicholls said.
"You wouldn't want to be changing a horse's diet so close to Cheltenham. It would have a massive impact, it wouldn't be increasing your chances.
"You'd almost want to be on the same hay, the same feed, the same diet. People do things so totally different.
"I had quite a lot of horses come to us from Willie's this year and it's taken them the best part of a year to get used to our routine. It would have been the same the other way round.
"It is quite a shock for the horses. It's not going to be an advantage moving so close to Cheltenham, that's for sure."