Edward Wright was diagnosed with selective mutism at the age two.
His mother, Michelle, says she wasn't worried initially but gradually she could not help noticing his silence.
The Daily Express quoted her as saying: "I was worried...He'd chat at home but if we were in a supermarket or at the doctors he wouldn't say a word. It was as if he was scared of people he didn't know hearing his voice."
"At nursery he'd point to pictures of what he wanted to do each day rather than telling the staff. At first we thought he was just shy," she added.
Although Edward's family could not understand his behaviour, his speech therapist said his symptoms showed he was suffering from selective mutism.
Edward's special coordinater suggested visits to a donkey-riding centre might help.
The Elisabeth Svendsen Trust (EST) For Children And Donkeys is situated on the outskirts of Leeds.
Every week nearly 150 children with disabilities and special needs spend time with the donkeys here.
Michelle explained: "The idea was that the games and activities Edward would do with the donkeys might help him overcome whatever was stopping him talking."
Edward attended sessions at the centre last September and showed marked improvement in the weeks to follow.
Michelle said: "Gradually he became more confident...after a few weeks he began whispering commands into the donkeys' ears. Later he would say instructions out loud to stop and start them while riding. It was lovely to see."
She added: "At school he now talks to friends in the playground and he answers teachers when they ask questions. Every day he has an hour or two of speech therapy which also helps.
"Edward talks about the donkeys a lot, especially his favourite one Eeyore. The donkeys really have helped him find his voice."