Puppy born with green fur on Italian farm named Pistachio

There are several theories behind Pistachio's distinctive colouring. Photo / Cristian Mallocci

An extremely rare lime green-coloured puppy – named "Pistachio" – has been born on an Italian farm.

The tiny pup was delivered on October 9 and was part of a litter of five from one of Italian farmer Cristian Mallocci's mixed-breed working dogs.

However, while Pistachio's brothers and sisters were all white, he arrived with a distinctive lime-green coat.

Mallocci, who lives on the island of Sardinia, told Reuters he hoped his unusual dog would spread some cheer around the globe during the deadly coronavirus pandemic.

He said homes would be found for the rest of the litter, but Pistachio would remain on the farm and eventually follow in his mum's sheep-guarding footsteps.

Pistachio's siblings were all white. Photo / Cristian Mallocci

The exact cause of Pistachio's unusual colouring isn't known, although one theory is that it could be caused by a bile pigment known as biliverdin.

It is found in dogs' placentas, and can mix with amniotic fluid during birth, which can stain light-coloured fur.

Another possibility for the green tint is meconium – a baby mammal's first bowel movement – which can enter the amniotic sac and colour the coat.

Whatever the cause, previous cases of rare green pups have proven the green tinge is only temporary, and will fade away as the hair grows.

While Pistachio is definitely rare, there have been several other green-hued dogs born in recent years with monikers to match, including Hulk the white German shepherd puppy, who was delivered in the US in January.