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Cows have about a one-in-two-million chance of delivering healthy triplets - so veterinarian Jenny Weston could hardly believe it when it happened in front of her.
A cow on one of Massey University's organic farms in Palmerston North, referred to as Number 26, had three male calves on Wednesday night.
Ms Weston, a senior lecturer at the university, said the chance of cows having triplets in New Zealand was about one in 500,000 but the chance of them being born alive was about one in two million.
Only one in four sets of triplets are delivered all alive.
Number 26, first thought to be having twins, started calving about 5.30pm, with herd manager Tania Smith monitoring her.
She called Ms Weston about 9.30pm to deliver the calves with the help of Meredith Lowe, a fifth-year bachelor of veterinary science student.
The pair managed to pull out the first two calves with some chains and rope.
"At that point I joked to Meredith, 'You'd better check for a third'," Ms Weston said.
"It's the golden rule that you always check for another. I thought she was having me on when she said there was another head. I couldn't believe there was another head in there, and then it bit me."
Even twins are rare, with only about 2 per cent of heifers having a double birth, Ms Weston said.
"Number 26 did surprisingly well. Usually calving is particularly difficult so it's always nice to get healthy calves, especially three."
The calves are considered quite small, weighing about 20kg each, but are healthy.
They are in a paddock with their mother but will soon be separated to ensure each is feeding properly.
Number 26 was brought up among a herd of 47 on an organic farm.
The cattle eat only organic foods and the grass is sprayed with organic fertilisers.
The 3-year-old Friesian/Jersey cross was impregnated by artificial insemination to a Jersey.
Her calves will also be brought up as organic cattle.
Ms Weston delivered triplet calves about 12 years ago in Taranaki but they weren't all born alive.
