Flies are bugging Cusack so he's getting fly wipe applied twice a day.
"Shaun is doing pretty good, learning how to be a horse and be part of the herd," Deb reports.
She says his ribs are gradually disappearing, and his topline is looking better.
"I think his grazing, moving with the herd and being free to gallop, trot and play has helped his body more than anything," she says. "OK, maybe not play. I'm not sure he knows how.
"Being with this herd has certainly helped his mind," she says.
"He's having a tough time with biting flies, so the fly wipe goes on a couple of times a day. I wish Pyranah was a sponsor!
"He seems happier today, and more at peace. I left him and the rest of the herd up in the shelter, out of the sun and flies.
"He eats as much at one sitting as the rest of my horses all together.
"He can really put it away, and he's still looking for more.
"I want to put weight on him slowly, and balance it out with building some muscle on him. He's looking shiny, too!
"Interesting 'before and after' for this guy."
Deb hopes Shaun will warm to a career in competitive trail riding, but for now he is enjoying life on the Kansas ranch putting on the condition that will give him a new lease on life.