With the help of owners Bonita Lionetti and Daniel Busch, Millie delivered a first litter of 20 puppies on Thursday last week, 18 of which are now healthy and thriving in their Prospect home.

A UK mastiff holds the world record for most puppies in a litter, delivering 24 in 2004, 20 of which survived the birthing process.

Miss Lionetti said she was amazed to think Millie could have delivered the biggest Australian litter on record.

‘‘We got an X-ray done and the X-ray showed probably 13 puppies,’’ Miss Lionetti said.

‘‘We built the whelping pen and did everything around the 13 puppies but she had other ideas.’’

After firstborn Max was delivered at 9.30am, Millie was in labour until 8.20pm the same day, when she finally gave birth to the last puppy.

The litter has since been divided into two feeding groups and spreadsheets have been compiled to document weight and identification marks.

‘‘We’ve split them into two teams – a green team and a red team – and we just rotate them, it’s a full time job,’’ Miss Lionetti said. ‘‘They have to be fed every three hours so we have to rotate them off (Millie) and make sure that she gets a break obviously, so she can have some time out as well.’’

Several puppies have already been named, including Tilly the runt, early alpha male contender Titan and BJ (Bronson Junior), who shares both the name and appearance of his sire.