The horses' owner Bianca Wogandt and her mother June, who was allegedly in charge of the daily care of the two mares, have pleaded not guilty to breaching their duty of care under the animal protection act.
The animal welfare watchdog removed the 11-year-old horses from a property at Dundathu last December following concerns for their health.
RSPCA inspector Penny Flaherty will allege that when she arrived at the property the horses were in "very poor condition and the RSPCA has evidence to indicate that they were underweight to the failure of the persons in charge to provide appropriate feed".
It will also be alleged that the seizure and prosecution followed "exhaustive long-term efforts by the RSPCA to educate and work with the persons in charge to improve the condition of the horses in a lasting manner".
The Wogandts pleaded not guilty in March and appeared in the Hervey Bay Magistrates Court yesterday where they said they would continue to contest the allegations.
A hearing mention has been set for May 27.