Head to the back of the farm to find David Geddes, who asks if you can assist his wife in delivering a foal. Along the way you’ll see his son, Duncan, who needs assistance with his horse, Jeremiah. Once you’ve calmed the horse, you’ll need to mount it and tire it out before it’s possible for Duncan to ride. You’ll have 45 seconds to do this and the quickest way is to continuously jump until you’re down to just the core, at which point you should gallop as fast as possible to drain it.
Once drained, you’ll need to head back to Duncan however before you do so, make sure you feed him an apple from the item wheel for the Gold Medal. Head inside and dismount the horse so Duncan can mount it and watch as he rides it around the corral until Mrs Geddes approaches you, wondering where you got off to. Follow her to where the foal is and help her deliver it by following the onscreen instructions.
Return to John’s house now and you’ll take Jack out for a riding lesson on his new pony. During the ride down to the stream, you’ll get the opportunity to tell Jack to slow down or speed up, don’t let him ride too fast or you risk him falling off and losing your Gold Medal. Once you reach the stream, the final part of this mission takes place, you’ll need to beat Jack back to the ranch which is easily done as long as you gallop the entire distance.