"He has got one of the best temperaments you will get in a horse and he just loves living life... that's why he keeps battling on," Salisbury said this week as Subzero continued his recovery from serious illness at the Bendigo Equine Hospital.

The 1992 Melbourne Cup winner known as the 'peoples horse' celebrated his 31^st birthday on Thursday and is displaying his trademark fighting qualities after being struck down by a case of colic, kidney problems and peritonitis.

There were genuine fears early in his treatment that "Subbie" wouldn't make it to his 31^st birthday, but on Thursday he marked the milestone with a cake and visit from the Salisbury family, who he has been with since retiring from racing in 1994.

"I'm very proud of the fight he has shown over these past couple of weeks to keep going, but I'm also very proud of the equine hospital and what they've done for him," Salisbury said.

"Without vets Sarah (Jalim) and Mike (Whiteford) he wouldn't be out here on his 31^st birthday today picking grass... I can assure you of that."

Subzero is one of racing's great ambassadors, much more than just a Melbourne Cup winner. Richard Freedman this week lauded him as the nation's greatest living thoroughbred given his impact on and off the track.

Together with his great mate Salisbury, the pair have done countless visits to schools, hospitals, hospices and retirement villages over the years, touching the lives of many.

And that's why there has been such an outpouring of support for Subzero during his health battle.

Such have been the frequent inquiries on Subzero's condition, the Bendigo Equine Hospital was posting daily updates on its Facebook page during his stay.

Salisbury says he has been overwhelmed by the messages of support for Subzero from across Australia and abroad.

"The following the horse has got is just unbelievable; there's been a lot of phone calls, emails and Facebook messages from not just across Australia, but Ireland, England, Scotland and New Zealand," Salisbury said.

"We've been getting well wishes every day from all over the world, so he certainly has a cult following.

"He has been good to a lot of people over the years... he's done a lot of visits to nursing homes, hospitals, hospices, schools and things like that.

"You add all that up over the 25 years he has done it for, there has been a lot of people who have got to know him over those 25 years."

Salisbury says that once Subzero is fully recovered from his health scare - he could be back at his Heathcote property on Saturday - the pair will once again get out and about on visits, although not as frequent as days gone by.

"I'll keep him going to the retirement villages; he might be able to do one or two of those a month and probably one or two schools a month... just enough to keep him occupied," Salisbury said.

"You get a lot of people who retire at 65 and if they're not doing anything they may not get to 70.

"But if they still keep occupied they may get to 90 and it's the same with him; while he's doing something he's happy.

"He's just a marvellous old horse and we're looking forward to getting him home again. If he's up to it he can have a couple of stubbies and carrots for his birthday and then we'll look forward to his next chapter."

Bendigo Equine Hospital vet Dr Sarah Jalim describes Subzero as one of the toughest horses she has treated.

"You have to be tough to win a Melbourne Cup and he still has the same fight he had in him back then," Dr Jalim said.

"Hopefully, he continues to improve and will be able to go home on Saturday."