Five horses were being transported from the stables to the Hunter Valley when the truck lost control and rolled about 10 minutes from Euroa on Creightons Creek Rd, just before 9 pm.
Local police, CFA and SES were called to the scene, with the truck needing to be cut open to free the animals.
It was discovered three Shadwell Stud fillies — Hafaawa, Aladaala and Maktabba — were killed in the accident along with a broodmare, while two-year-old filly Hybrid Theory, which ran fifth in The Showdown at Caulfield on Saturday, survived.
Hybrid Theory was not a Lindsay Park-trained horse, rather a member of Sydney-based trainer Bjorn Baker's team.
The driver, who was working for external company Platinum Transport, was not physically harmed.
Nagambie police Leading Senior Constable Jason Woosnam said police, CFA, ambulance staff, three vets and stock removalists all attended the scene, with police there until 1 am.
He said the cause of the crash was being investigated.
Commander Paul Scragg said the CFA was called because gas was smelled at the scene, with the crew assisting with the extraction of the horses once it was secure.
He added emergency crews had done a marvellous job addressing "not an everyday occurrence".
Lindsay Park co-trainer Tom Dabernig, who attended the scene with three senior veterinarians and senior stable staff, described it as “shocking”.
“I feel for all the people that had to witness it and that were involved, trying to help what was just an awful situation,” he said.
“From that point of view, we owe a big ‘thank you’ to everyone involved: the CFA, SES and local police. It was a confronting scene; we had three senior vets, senior Lindsay Park staff — everyone chipped in and it was a big team effort.
“If you’re an animal lover, and particularly a horse lover, you just hate to see that suffering and distress. It was great to see the vets and how professional they were. Full credit to them for how they handled an awful situation.”
Two of the horses were killed instantly, two were euthanised soon after while local vet Stacy McGregor was caring for Hybrid Theory, which had minor lacerations but no career-ending injuries.
The three David and Ben Hayes and Dabernig-trained fillies had combined for five wins from 26 starts and $172 600 prize money, but were more valuable as breeding prospects due to their stellar pedigrees.
Mr Dabernig said the stable owed the local authorities a debt of gratitude for their efforts in working through a terrible situation.
“They were impressive, and on behalf of Lindsay Park we would certainly like to thank them publicly,” he said.
“It can be hard to do that at the scene at the time with everyone focused on getting the situation sorted, particularly under the dark of night when you hardly know who is who. Those involved put in a great team effort — we’re very thankful for that.”