Some winter calves are dropping earlier than expected - and it might be down to the sperm, Federated Farmers dairy chairman Andrew Hoggard says.
Mr Hoggard milks about 500 dairy cows in the Manawatu and has calves already on the ground, two weeks earlier than expected.
Spring calving usually happens anywhere from July to September, with most milk being produced between October and December.
Mr Hoggard said over the past several years he's noticed the calving dates getting significantly earlier.
"They are starting to come a bit earlier, we've got a few calves in the shed that are full term. Normally you do expect them to come in at this time, although these calves have been in the shed for a week or so."
It might be because of the semen used, he said.
"I've been using short gestation semen to compress the calving pattern, the last week of AI (artificial insemination) I used the short gestation so there is that - I've introduced this genetic trend into the herd, whether or not it's having an impact I'm not too sure."
It had been the earliest they've ever calved, but the winter has treated them well, Mr Hoggard said.
"This winter has definitely been one of the mildest and easiest winters I've had to deal with, we've been having really good grass growth, on average we've been growing about 20kg a hectare a day. Last year in July it was pretty horrible and we were only growing at about 5kg a day."