The Kirkham's farming business consists of four dairy farms milking over 2700 cows in total, as well as a calf rearing and grazing unit.
Within the wider operation are three dairy farms all located in a close radius, 10km south of Te Awamutu.
"The cluster of three farms are within a stone's throw of each other," operations manager Brad Eyre said.
"They are run under the same management and feed systems, with comparable contour and pasture growth which puts us in a unique position of being able to make these comparisons."
Eyre is the Kirkham's nephew and joined the business 13 years ago, starting as a contract milker before progressing to operations manager in 2016.
He admitted he was not in favour of maintaining the Jersey herd when he started with the Kirkham Group.
"When I first came to the farm I wanted to cross the Jersey herd."
However, that didn't eventuate and now the group have a Jersey herd (Pepi Oaks), a Friesian herd (Allen Oaks) and crossbreed herd (Oakwood) as part of their home cluster at Tokanui, with a further dairy farm at Waiterimu, milking crossbreed cows.
The three central farms are stocked at a similar liveweight per hectare and have the same inputs including maize, palm kernel, kiwifruit, and grass silage.
While Jersey's efficiency is well proven, it is sometimes argued that the per animal costs associated with a higher stocking rate can offset the advantage.
This is something the Kirkham's figures challenge.
"Pepi Oaks has the lowest farm working expenses of all three farms in the cluster at $4.37 per kg of milksolids," Eyre said.
The other two farms in the cluster have farm working expenses of $4.86 (Friesian herd) and $4.77 (crossbreed herd).
Jim Kirkham believed the quality of the herd set Jerseys apart.
He put the success of his Jerseys down to the efficiency of the breed and their suitability to their system 4 operation.
"Pepi Oaks sits comfortably within the top 5 per cent of New Zealand herds for both breeding worth and production worth and was established by my father back in 1975 so there is a lot of history behind it."
Kirkham's father came to Te Mawhai in 1960 and originally milked shorthorns but had to cull his herd after an outbreak of TB - which he replaced with Jerseys.
"Dad purchased a line of heifers from Hodable Farms who were the first people in New Zealand to do artificial breeding.
"It was a good line of stock and we continued the practice of artificially breeding yearlings, something we have done with all our herds."
The combination of Premier Sires and AB mating yearlings for 30 years has helped to drive genetic gain.
Pepi Oaks have a breeding worth (BW) of 194 and a production worth (PW) of 220, while Allen Oaks (Friesian) has a breeding worth of 110 and production worth of 124, and Oakwood (crossbreed) a breeding worth of 127 and production worth of 140.
The same approach to mating is taken with all three herds – with four weeks of AB followed by four weeks running bulls, and finishing with two weeks of short gestation semen.
This year the farms will use sexed semen for the first two weeks of AB over the top 25 per cent BW cows and put the bottom 20 per cent to beef.
For now, the group is happy to have a foot in each camp when it comes to their breeding and have no plans to convert to all Jersey.
"These things tend to be cyclical, but right now we are very happy with the performance of our Jersey herd," Eyre said.
"My grandad will certainly be happy I didn't cross the Jerseys."
