They could feed it something, I'm sure. Or the prop guys had to whip something up. :lol
I loved that they kept the ceremony scene straight from the book like that. They had to have known that faithful readers were expecting to see the horse poop. Nice of them to include that for us, eh?

I was wondering if they'd allude to the fact that the Kingsguard were off knighting people for several hours. It just baffles me why they didn't seize the perfect opportunity to start delving into the back story when Dany enters the HotU, though. Seemed like the perfect chance to show Rhaegar, Aerys, and some others. Or at least start hinting at some of the major prophecies.