Watch: Quadruplet calves amaze farmer

A South Taranaki dairy farmer says he got the surprise of his life when the twin heifers he was helping deliver turned out to be triplets, then quadruplets.

When Michael Kavanagh and his parents converted their 100ha farm near Maxwell from dairy grazing to dairy production in 2015, they purchased the majority of their Friesian herd from a farm near Stratford where they routinely named their cows.

During a routine check of the springer mob last month, Kavanagh discovered one of these cows, 6-year-old Becky, beside a small heifer calf in the paddock. He helped her deliver a second heifer, before discovering a third.

"At this stage I was pretty amazed, triplets are rare, but not unheard of. In 11 years farming, I'd not come across them myself though. After checking they were all healthy, I sent out a Snapchat to my friends saying 'triple the fun', but a little while later, the joke was on me."

When he checked Becky's uterus for tears, Kavanagh says he discovered a fourth heifer hiding inside.

"I couldn't believe it. She was a big Friesian cow, but these heifers still weighed around 30kg each, which means she'd been carrying in excess of 120kg around."

Despite calving three of the four heifers himself, Kavanagh has DNA sampled all four and sent this away to LIC's GeneMark laboratory to confirm parentage.

"Two other cows calved at the same time as Becky - both had healthy sized Hereford-crosses. The only cow that was showing interest in Becky's first calf ended up calving five days later, so it couldn't have been hers. We really want to be sure though."

Kavanagh says even the vets were amazed Becky managed to carry all four embryos to term. "Because the four heifers are not identical, that means they originated from four embryos. Normally the cow drops any other potential embryos and only holds on to the strongest, but obviously, in this situation, she held on to all four."

He says the vets explained it's an extremely rare occurrence and none of them had first-hand knowledge of quadruplets before.

"My friends have carried out a bit of research and sent me links to quadruplets in Ireland and Texas, but we haven't been able to find any documented cases of quadruplets in New Zealand.

"Someone told me there's a one in 11 million chance and that I should buy a Lotto ticket, but I haven't won yet!"