The royal was joined by the Duchess of Cornwall as they met with farmers and visitors at the event.
Judge Anne Tully, from Brixham, Devon, told him not to worry and to even expect good fortune after he stepped in the cow pat.
“I told him that was luck, that’s what we always say," she said.
The prince then came face to face with champion 1,550kg Hereford bull Moralee One Rebel Kicks, owned by Tom and Di Harrison from Stocksfield, Northumberland.
Mr Harrison said afterwards: “I could have talked to him for an hour.
“He is very knowledgeable and I would have liked to have bought him a pint.”
Charles also spoke to mother Hannah Richardson, from Ripon, who brought her eight-month-old baby Phoebe to the show.
Afterwards, Mrs Richardson said: “I can’t believe she has met the prince – this is the first big event she has been to because of lockdown.”
The royal couple joined thousands of visitors at the agricultural show – a key event in the farming calendar – in Harrogate, North Yorkshire, which was cancelled in 2020 due to the pandemic.
Charles is patron of the event and he was due to meet farming experts, look at livestock and see some of the 2,000 stalls at what is England’s biggest agricultural show.