Any insurance claims people believe they have in relation to Black Caviar's half-brother is a matter for the administrators of BC3 Thoroughbreds, William Inglis and Son boss Mark Webster says.

BC3 signed a record $5 million contract at the Easter Yearling Sale to buy the colt but the auction house never received payment and Inglis repossessed him when BC3 collapsed earlier this month.

The colt, known as Jimmy, was euthanised on Sunday after succumbing to the hoof disease laminitis.

BC3 Thoroughbreds is now in voluntary administration. Its former chairman Bill Vlahos is being sued separately over missing millions from a so-called punters' club but has now filed for bankruptcy.

Inglis insisted `Jimmy' be insured and noted its interest in the colt on the insurance policy with a London-based underwriting firm, Webster told Melbourne Radio station RSN on Monday.

"There seems to be coming out in the media a whole range of people that have given money to (former BC3 chairman) Bill Vlahos for various reasons and it's very, very difficult for us to get our head around that," Webster said.

"And from our perspective, our position with Jimmy is we're a secured creditor and of course the way that the law works that ranks ahead against any unsecured creditors.

"So the unsecured creditors really need to be in liaison with the administrators to understand what their position is going to be."

Webster said breeder Rick Jamieson had retained 10 per cent.

"But the others, their claim is really with the administrator of BC3 Thoroughbreds along with all the other creditors that are currently dealing with the administrator."

The half-brother to Black Caviar contracted laminitis after an adverse reaction to antibiotics given to him for a swollen leg two months ago.

Webster said Inglis maintained security over every horse it sold until they received payment.

He said the administrators of BC3 Thoroughbreds had not challenged that.

"In fact they have recognised our security and we were entitled to note that interest on the insurance policy, which we have done," Webster said.

Webster said the decision to put the colt down was made in consultation with the veterinarian appointed by the insurance underwriters in London.