"And I think Michael [O'Leary] likes the Angus because they're a bit like his airline - low cost, low maintenance."
When the West Cork native first came to work at Gigginstown 15 years ago, he had very little experience of working with horses.
"But as Michael said to me, he doesn't need to know how to fly an airplane to run an airline," smiles Mr O'Mahony.
It's a testament to the ability of Joe and the rest of the farm staff at Gigginstown that the operation has developed so much during the last 15 years. "When I arrived there was just one racehorse and 10 mares. Now there's something like 200 horses, 140 cows and 100 commercial angus across the enterprise.
"The horses really just come here on their summer holidays when the hunt or flat season ends, and the space they get here allows them to recharge," he explains.
Despite the attention that the horses get, the pedigree angus herd is treated seriously too, with top class foundation stock imported from Canada and the UK in the early days.
"We're almost a closed herd now with just a few select females and maybe one new stockbull bought in every year," says Mr O'Mahony.
The bulls and heifers on offer this Saturday were all born between September 2014 and March 2015, with a few of the heifers already calved down before sale day.
As O'Leary himself says, "it's probably one of the best groups of animals we've ever offered.
"They're stronger, and all four- and five- star rates," adds Joe.
All the animals will be BVD and Johnes free, and vaccinated for blackleg, BVD, IBR and leptospirosis.
Many of the lots include top breeding from bulls such as Krugerrand, Extra Gold, and Black Magic, with some of the heifers in-calf to a new prize-winning stockbull purchased from Albert de Cogan, Rosemead Karona.
While the bulls are selected for the sale on the basis of their daily liveweight gains, with all of them averaging 1.5-2kg per day, Mr O'Mahony stressed that the system at Gigginstown was not designed to 'hot-house' them.
"They're kept in converted stables on peat bedding, and fed about 8kg of meal a day with chopped straw and hay," he says.
Heifers and cows are all on a wholecrop and silage diet, and soon to be turned out.
"We don't spread much nitrogen on the grazing ground, to prevent it being too high in nitrogen for the horses.
"So the grass is later coming here. All the autumn calvers will be going to grass this week," he said.
Whatever the system is, it appears to be working.
Over 90pc of the herd's offspring sold as breeding stock to breeders from both north and south of the Border.
The Gold Cup will be available for selfies - O'Leary
A large proportion of the crowd at the 10th annual Gigginstown sale this Saturday will be hoping for a glimpse of superstar horses and, of course, the man himself, Michael O'Leary.
"God help them!" is the Ryanair CEO's good-natured response, but true to form, the Mullingar native will have plenty of crowd pleasers at the event. "I'll be there, but sure I'm out at under 10s rugby training and swimming lessons here every Saturday, so it's no big deal.
"But I like to do it because it's a bit more interesting than just selling all the stock through the local mart.
"We'll also have some of the horses, like War of Attrition and Last Instalment, and of course the Gold Cup for selfies," said O'Leary.
The auction is slated to take place on Fennor Farm, one of the operation's four out-farms.
Does he see the Gigginstown operation expanding any further? "Not really. I think there's enough for Joe and the team to manage. I've got four children, and I don't want to be handing on some ludicrous amount of land," he says.
So is there a budding farmer in the family? "The eldest is seriously impressed with the contractor's machinery at the moment, but that might be a phase. We'll see," he chuckles.