Not to step on Edna's toes about the urine subject, I hope someone can answer her. I actually have a similar question. This happened after my first LD last November when we got home.
I noticed pale yellowish white stringy (like half-cooked eggs) matter in my mare's poo. It was wrapped around each terd like a membrane. Very weird!! I've been too embarrassed to ask about it (why, I don't know because it's not MY poo we're talking about) until Enda brought up this one.
Anyway, I've looked all over the internet, but honestly, how do you Google "pale yellowish white stringy (like half-cooked eggs) matter in my mare's poo?" I'm mean, really.
I thought it may have something to do with lactic acid production due the physical stress of the ride? I have no idea. If anyone has ANY idea bout this, please let me know. But answer Edna's post about the pony first. :) Thanks, gang!
~Carrie <\_~ // \\
"The wind of heaven is that which blows between a horse's ears."