Veterinary surgeons in Kentucky are encouraged by Rachel Alexandra's improvement with the champion mare in a serious but stable condition after abdominal surgery.

Rachel Alexandra underwent the surgery after she suffered complications from foaling last week.

The 2009 United States Horse of the Year went for a short walk outside on Monday and ate a small amount of grass.

"If she wasn't as smart and as strong-willed as she is, she wouldn't be progressing the way she is," Dr Bonnie Barr said.

Stonestreet Farm said she remained bright with normal vital signs.

On Saturday, a small amount of feed was introduced in addition to her IV fluids and nutrition.

Her Bernadini filly foal is now being cared for by a foster mare at Stonestreet Farm and is doing well.