Your Uncle leaves you alone in the stall to give your changes a chance to finish up in privacy. You take a moment to feel your face; you're quite sure its extended further than when you'd last seen it in the bathroom. Your nose in particular feels much thinker. You almost wish you had a mirror to observe your changes, but the memory of your face's reflect in the bathroom mirror stops you from asking.
A rumbling in your stomach reminds you you hadn't eaten since this morning. You didn't even think to ask your Uncle to bring you anything. You look around to see if there's anything to eat. A quick glace around the barn serves to prove your memory correct; all you can see is the hey. Oats you could probably handle but where you changed enough to eat straight up hay? You consider heading back to the house, but you aren't sure if your uncles farmhands are still around. You're quite sure the sight of a half-man, half-horse for freak them out, to say the least.
You lower yourself onto your hands, noticing that the middle fingers on each hand are beginning to extend as well. Given the changes to muscle and configuration of your legs, the position is much more comfortable than you;d expected. A strange poking sensation had also made itself know about your rear, what you assume to be the start of your tail.
You reach out with your newer, more horse like lips, unsure how exactly to eat like this. Surprisingly, your lips are much ore flexible than you'd expected, and you find yourself somewhat able to pick up bits of hay. The taste is rather bland, as you'd expected, but the texture wasn't too bad. Even the excessive amount of dust doesn't bother your new mouth too much, although you do end up sneezing a fair bit, You at least try and aim your much larger nose away from your meal. Within minutes you find yourself gorging, almost entirely focused on filling your expanding stomach and oblivious to your surroundings.
After a time you really start feeling the heat of the barn. Even naked, a fine layer of sweat is covering your darkening hide. A distinctive horsey smell is filling the air, but you don't seem to mind it as much as you did while looking after your uncle's horses. Must be getting used to it, you think.
Hunger satisfied for the moment, you raise your head to look around, forgetting where you'd seen the troiugh of water earlier. The idea of drinking out a trough filled with horse spit and lord knows what else didn't seem particularly appealing, but you'd have to do it for the next few day, so you figured you might as well get used to it. The dry hay had left you feeling rather uncomfortably dry. With little warning, you feel your bowels start to cramp, and you know whats coming. You look around for a more preferable place to take a dump, but the decision is quickly taken out of your hands as your now bushy stub of a tail lifts and you begin uncontrollably dropping your load of horse manure on the barn floor. The relief is short lived as the smell quickly reaches your nose. Rather pungent, but not as bad as even the smell you'd been slowly getting used to over the past day of barn work.
Finished, you try to raise yourself back onto your legs, now hind legs. It takes some effort, leaning against the wall, but your able to. You aren't quite ready to be down on all fours, not quite yet. You notice how significantly taller this makes you, just a few inches short of what you might reach on your hind legs once you finishing transforming. The effort has made your skin slick with sweat now, and so much so that you can see it forming even under your slowly thickening fur. You've clearly grown much more in size, even since entering the barn the second time with your uncle.
Suddenly another smell overpowers your nose, similar to the smell coming off you, only much more...oh. Your new ears twitch, and you detect the distinctive sound of clopping hooves. Looking out towards the entrance, you spot the same mare you'd had your fun with earlier, only now you were able to detect the obvious scent of her heat. You weren't expecting to see her, or any of the other mares back so soon; your uncle had promised to bring them back in once he'd figured you'd be finished changing. If anything, she seemed to you more beautiful now than even during your previous encounter earlier that day. The sight and smell cause an immediate reaction in your now much further changed member, and you found yourself wondering if your new size would be sufficient.