Samples taken from batches of horse pellets which formed part of Ortensia's feeding program leading into the Group One Galaxy have not detected the prohibited substance ractopamine.

A post-race urine sample taken from Ortensia after she won the Galaxy at Randwick in April tested positive to a prohibited substance, later revealed to be ractopamine.

Racing NSW obtained samples of a pellet feed product last month and sent them to the Australian Racing Forensic Laboratory for analysis.

A statement from Racing NSW on Friday said that an analysis of samples taken from six batches of horse pellets provided by a stock feed manufacturer, whose product was being fed to Ortensia leading up to the Galaxy, had not detected ractopamine.

Stewards' investigations into the findings of ractopamine in the mare's post-race urine sample were continuing, the statement said.

AAP