Mother and sons training partners Barbara Joseph and Paul and Matt Jones have been suspended for four months over the death of a racehorse in their care.

The three were charged by stewards on Wednesday with failing to provide the necessary veterinary treatment for I Am Rocky, who died in February after displaying symptoms of colic.

Stewards initially issued a six-month penalty but reduced it to four months because of several factors, including the trainers' guilty plea and the fact it was their first offence under any related rule.

Joseph, who has trained top gallopers including Group One winner Merimbula Bay, entered a training partnership with Paul Jones in 2010 with their operation based at Thoroughbred Park in Canberra.

Matt Jones was officially licensed last year after working as a foreman for the stable.

Stewards have given them seven days to organise the transfer of their horses to other trainers with their suspension to begin on July 4.

They were also fined $200 for failing to lodge a stable return for I Am Rocky when the horse joined their stable