And while he wouldn't do it again, the central Victorian horse trainer is happy to have conquered the epic cross-country ride and counts the friendships he made among the highlights of the experience.

Mr Donaldson-Aitken, of Coghills Creek, crossed the finishing line on July 31 with fellow Australian Howard Bassingthwaight in joint sixth place after covering the 1000km in nine days and swapping horses every 35km.

"Once I got it completed it wasn't about the race, it was about the people and close friends I made and riding with them," he said.

The adventure ride roughly follow the world's first long-distance postal transmission route, laid down by Genghis Khan in 1224.

Riding semi-wild Mongolian horses for 11 hours a day, and covering up to 130km, Mr Donaldson-Aitken suffered general soreness and sore hips but it was the "mental grind" that hurt the most.

"The last couple of days it was a bit of a grind mentally," he said. "I didn't sleep well as it was really cold just sleeping on the ground ... and toward the end I was getting a bit short and moody."

"You get mentally sick of counting down the kilometres."

Every 35km the riders stopped at a horse station, known as morin urtuu in Mongolian, where their horse must pass a vet check before riders can select their next horse, grab supplies, and keep going.

Passing the vet check meant riders had to choose their horses well and strictly manage their exertion as they covered the countryside.

"You're always counting the kilometres. You get down to 15km (to go) and give the horse a break, a relax and a drink, then trot from 10km out then slow down again and from the 2km mark you might walk or get off the horse, then maybe 1km out take the saddle off if you think the horse is still hot or its heart rate is still high."

Warm weather on some days meant horses would dehydrate more quickly causing their heart rate to remain elevated, and several riders incurred vet penalties as a result.

Mr Donaldson-Aitken spoke to a previous Mongol Derby winner for advice, who told him to carefully choose his horses and opt for bigger steeds because of his size - something he said put him at a slight disadvantage because some of the women riding were much lighter and their smaller horses' heart rates did not get as high.

The horses used in the derby are semi-wild, donated from local herding families who have trained them and turned them out on to the steppe.

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Some riders fell off and were injured, particularly when first getting on the horses, and some had horses run away from them leaving them stranded in the wilderness and reliant on local herders to help them, but Mr Donaldson-Aitken said the horses were not as bad as he expected.

"When you get on the plunge and rear a bit but once you kicked them around and got going they rode pretty true," he said.

He said the terrain across the 1000km course was quite hilly, with some mountain areas but a lot of the land was very much the same - rocky, shaley country with the same type of grass as far as the eye could see.

When Mr Donaldson-Aitken arrived in Mongolia, his riding gear had been lost somewhere between Australia and Seoul but it was eventually delivered to him the night before the race began - after he had scrounged and borrowed gear from other riders and been officially weighed in.

He was able to swap some of his own items in and keep the same weight, but it was a frustrating start to the event.

"I wouldn't do that again and none of us who did it thought we would do it again. We saw a fair bit of Mongolia and got a fair idea about what the country is about, what the horses are about, and I don't think I left anything on the field," he said.

"Every single person in the race in the end of it got out of it what they wanted. I rode with good people and in the end no matter where you are, the quality of people you are around makes the trip.

"I was lucky to meet people that were my type of person. We were all each other's type of person."