Without hesitation, she texted the repairman, asking him to fix it as soon as possible.

Maintaining cows at cool temperatures is critical because heat stress in dairy cattle can sharply decrease milk production and reproduction while increasing the risk of disease and mortality.

This could be a significant challenge for operating a dairy farm in Arizona, where summers keep getting hotter. Despite that obstacle, Arizona is the 14th highest milk-producing state in the U.S.

Arizona's cattle industry began with Spanish settlers and missionaries, evolving into a major part of the state's economy by the late 1800s and helping shape the culture and identity of the Southwest.

Cowboys became iconic symbols, and ranching communities thrived in many parts of the state. This cultural significance, alongside the economic importance of cattle, solidified its place as one of Arizona's foundational Five C's.

While early ranchers primarily focused on beef, Arizona's dairy industry began expanding in the 1970s, growing steadily alongside the state's population, reaching its peak in 2022.

Much of this growth can be attributed to methods studied by researchers at the University of Arizona since the 1960s to maintain cool temperatures for dairy cows, such as the use of shades, fans and water misters to create evaporative cooling.

Millican remembered seeing pictures as a kid of the first shades implemented for cows.

"They were like made out of palm fronds," Millican said. "This is all history because almost every cow in Arizona has cooling now."

That has been the standard since the beginning of Stotz Dairy farm, founded in 1981 by her parents, Tammy and Tom Thompson, in partnership with the Rosztoczy family.

A farming legacy for a family

The Thompsons were not always part of the dairy industry.

"Both of my parents actually grew up as city kids in California," Millican said.

Although her grandma sent her father, Tom Thompson, to work on a farm every summer break "to keep him out of trouble," Millican said he ended up liking it so much that he kept getting more involved in the industry.

He later connected with a family in Arizona interested in starting a dairy, and shortly after marrying, the Thompsons moved to Arizona to begin what would become Stotz Dairy.

Millican was born a couple of years later. She grew up on the farm and worked there during summer vacations throughout high school and college.

She earned a degree in dairy science and agribusiness from California Polytechnic State University, San Luis Obispo.

"Freshman year, I remember I called my dad and told him that I wanted to take over the dairy,” Millican said. “And he told me that that was my brother's job."

For a couple of years, she stayed away from her family business. She lived in California with her husband and worked in a bank. But when her first daughter was born, she realized how much she missed life on the farm and wanted her kids to experience a happy childhood like hers.

Millican returned to her native Arizona to work part time on the dairy farm.

"My brother was managing the dairy," Millican said, "I was just doing the tasks that other people didn't want to do, really."

One day some years later, while she was working part time and raising her third son, her brother announced that he was moving to California, where his wife is from.

"That's when my dad was like, 'Hey, you remember I told you that it was your brother's job? Well, it could be your job if you want it.'"

Millican has been managing the dairy ever since, while her father continues as CEO.

Arizona's evolving dairy landscape

The Stotz Dairy farm started in the 1980s with 539 cows and only four employees. It now has over 7,000 milking cows, along with over 6,000 heifers — female cows that haven't yet given birth — and calves, and around 150 employees.

The number of dairy farms in the state has decreased to one-sixth of those that existed in the 1960s, according to Julie Murphree, strategic communications director of the Arizona Farm Bureau Federation.

Yet even with fewer farms, Arizona remains a major dairy producer because "the smallest dairy in Arizona is large compared to those in the Midwest," Murphree said. "Our smallest dairy farm has about 800 milking cows."

It would be challenging for a small dairy to afford a cooling system for the cows, making it more cost-effective for larger farms to thrive here.

Murphree said that despite the large size of Arizona's dairies, about 94% of them are family-owned.

According to a report from the U.S. Department of Agriculture , last year, Arizona's dairy industry was the second-largest agricultural commodity in the state, generating nearly $1 billion in cash receipts.

It was number one in the previous three years and has remained in the top three for the past decade and a half.

At a national level, dairy consumption has declined over the last decade. Some speculate that the popularity of dairy substitutes such as almond, oat, soy and coconut milk has contributed to the slide.

Many Americans are shifting to plant-based foods for health and environmental reasons, according to a report from the Yale Program on Climate Change Communication.

While organizations like the UN suggest that reducing dairy intake can significantly lower environmental impacts , the USDA continues to promote dairy consumption for its nutritional value.

Environmental organizations such as WWF have identified the dairy industry as a significant contributor to air, water and soil pollution. But farmers say they are committed to adopting better sustainable practices and reducing their ecological impact.

Murphree said Stotz Dairy is a good example of this commitment and innovation in the industry, so much so that in 2014, the Thompsons were recognized with the Environmental Stewardship Award.

Stotz Dairy's sustainable practices

Much of the food we consume has some type of environmental footprint, but many dairy farmers commit to reducing that impact in different ways.

At Stotz Dairy, about 40% of the cows' diet consists of recycled food, including unsold fruits and vegetables from retailers like Walmart and Sam's Club.

The farm also cultivates some of the cows' feed, including sorghum, corn and alfalfa, using drip irrigation to conserve water. In 2013, they installed 992 acres of drip irrigation in the farming operation.

Water used for cleaning is recycled for irrigation, and cow manure is composted for crops. A methane digester converts manure into renewable energy, reducing odor and water evaporation.

Despite all the efforts modern farmers make to meet the expectations of caring for the environment, some activist groups argue that large farms displace smaller operations, contribute to climate change and deny animals access to open pastures.

Critics call farms with over 500 cows "Concentrated Animal Feeding Operations," "mega-dairies," or "factory farms," a term Millican dismissed.

"That term is usually used to disqualify," she said. "It was invented by people who don't know better."

The activist group is working on a bill to ban "mega-corporations" in the farming industry.

"Methane digesters are a solution to the climate impacts of this industry," Heinzen said, "but creating it unnecessarily only to capture a fraction of it and then burn it is not what we would consider environmentally friendly. We would like to see that methane avoided in the first place."

She said her organization thinks that "the whole thing is a greenwashing scam and is definitely the opposite of environmentally friendly farming."

Nothing is entirely black or white

At Stotz Dairy, there are two cow breeds: Holstein and Jersey.

Holstein, known for their iconic black-and-white spots, is the most common breed in dairy farming. They produce more milk. On the other hand, light brown-furred Jersey cows make less milk but what they do produce is higher in fat and protein.

" I guess the simple way of saying it is that Holsteins make milk that is good for drinking, and Jerseys make milk that is good for cheese and ice cream," Millican said.

She jumped into her truck and headed toward the milk barn. Along the way, she waved to the drivers she passed, and everyone, accustomed to this tradition, returned the greeting with a hand wave and a smile.

Arriving at the barn, she greeted the workers and spoke with most of them in Spanish, their native language, showing a valiant effort despite some mispronunciations.

Stotz Dairy has hired qualified individuals from Mexico with expertise in cow care and dairy farming, contributing to the farm's skilled workforce.

At the milking parlor, the cows formed two lines to be milked. A couple of workers cleaned the udders and connected them to the machine that extracts the milk.

The milk comes out at a temperature above 100 degrees and runs through the tubes connected to storage tanks. On its way, a plate cooler lowers the temperature to 36 degrees.

Around 15 trucks come to the farm daily to take the milk from the insulated silos to the United Dairymen of Arizona processing plant in Tempe.

The cows are milked three times a day, every day. Each milking takes about 10 to 15 minutes.

"When they're done, they come back out to their pen," Millican said.

Immediately after one group of cows left, another entered, and so on.

The cows produce enough milk to pay for their stay on the dairy farm for about seven years, the length of their reproductive period. They are impregnated through artificial insemination approximately once a year, and when they stop producing enough milk, they are sold for beef.

Cows eat side by side in a line, with their heads poking through a metal fence. They are also milked in line connected to large machinery.

At a glance, the farm works in a consistent, high-scale manufacturing way, which may be part of the reason some people call this a factory farm.

Still, Millican said her cows are happy and claimed they would not produce enough milk of such good quality if they were not content.

Stotz Dairy reports its cows produce approximately nine gallons per cow daily, totaling 3,285 gallons per cow annually, which translates to about 28,374 pounds. That number is above the average yield in the U.S.

"We're doing everything we can to make sure that the cows are living their best life and producing the best milk so that people can enjoy it without worrying about it," Millican said.

Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust .

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