Samantha Tennent pulls on a yellow hi-vis vest before entering a barn the size of eight rugby fields.

The sprawling shed west of Willmar in the United States' state of Minnesota houses 9500 dairy cows and is owned by Riverview LLP.

A truck mounted with a red Supreme feed processor drives down one of the shed's 12 lanes, spitting out a mixed ration to waiting cows.

This is dairy farming on a massive scale.

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The cows are milked twice a day through a spotless 106-bale De Laval rotary milking shed, which spins for 22 hours a day.

"The milking shed is extremely efficient. Each rotation takes 7.5 minutes," said Tennent, the chairwoman of Marton Young Farmers.

"Milk is pumped directly into a waiting milk tanker. The farm produces enough milk to fill nine tankers each day."

The cows walk onto the rotary platform in single file.

Three staff work at the cups-on area. One sprays each udder with disinfectant, another wipes the teats clean and a third secures the suction cups onto the teats for milking.

Tennent visited the United States last month as part of the International Federation of Agricultural Journalists (IFAJ) Alltech Young Leaders programme.

The trip included a leadership boot camp, attendance at the IFAJ's annual congress and several field trips.

One of the tours was to Riverview LLP-owned Louriston Dairy. Forty staff are employed to milk, feed and care for the farm's 9500 cows.

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The herd is more than 40 times larger than the average US dairy operation.

It is part of a network of giant farms built and run by Riverview LLP in Minnesota, South Dakota, Nebraska, New Mexico and Arizona.

The company owns 92,000 dairy cows, according to the Star Tribune newspaper.

"It employs about 1200 people. Once you've worked on one of the farms for two years you can buy shares in the business," Tennent said.

Louriston Dairy was built in 2017, reportedly costing $US50 million. Construction took eight-and-a-half months and involved large earthmoving equipment.

Cows from a 9500-strong dairy herd are housed indoors in Minnesota. Photo / Supplied
Cows from a 9500-strong dairy herd are housed indoors in Minnesota. Photo / Supplied

A concrete pad, which is covered with two massive stacks of alfalfa (lucerne) and corn silage, sits alongside the barn.

The farm hosts tours and has an education centre which co-ordinates school visits.

The company even runs a summer internship programme, giving university students opportunities to gain hands-on experience.

Tennent, who works as a Palmerston North-based animal and feed developer for DairyNZ, visited several dairy farms during her August trip.

One of the other farms was significantly smaller. It milks 400 cows year-round.

The herd is also housed indoors, with most of the cows' feed grown on the farm.

"Those cows were milked three times a day," she said.

"Their feed consisted of ground corn, a custom protein mix, cottonseed, dry hay, ryegrass silage, haylage and corn silage."

The herd is run in four mobs, based on production level and stage of lactation.

"The different mobs are fed the same mix but in varying amounts, ranging from 24 kilograms of drymatter to 29.5 kilograms of drymatter per cow."

The farm supplied a local cheese factory and products made from the milk are sold on the domestic and international market.

Tennent's key learning from her time in Minnesota is that dairy farmers in the US and here in New Zealand have similar struggles.

"We farm very differently and we feel like we're up against the world from our little country here in New Zealand," she said.

"But despite the operational differences, the farmers I met talked about the same challenges we face here."

Labour was one of the biggest issues; trade and markets was another common theme.

"There was mention of difficulties with broadband, rural healthcare, climate change. It sounded very familiar."

The Marton Young Farmers member is extremely grateful to Alltech for what she describes as an "incredible opportunity".

"My awareness of the world has increased. I thoroughly enjoyed getting to know people from a range of cultures."

Next year's IFAJ Congress will be held in Denmark in June.