Veterinary surgeons treating champion mare Rachel Alexandra are encouraged by her progress.

The 2009 United States Horse of the Year remains in a serious but stable condition after abdominal surgery following complications from foaling.

However, doctors reported she was bright and alert and received a small amount of feed on Saturday in addition to IV fluids and nutrition.

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

Rachel Alexandra was herself raised by another mare when her mother Lotta Kim rejected her.

"Rachel's attachment to her own filly in the short time they were together, was deep and it is important now to support her surrogate, Miss Beutiful Ojos, as she steps into this difficult situation to raise that filly," a statement on the Stonestreet Farm website said.

"Miss Beutiful Ojos is a quarter horse and trusted nurse mare who has performed this important job at Stonestreet before."

The filly will stay with her foster mother until she is weaned.