I was standing beside a row of rocking chairs in North Dakota, looking out over the Badlands at a beautiful sunset, when a man who had heard me speak earlier at the Theodore Roosevelt Presidential Library started talking to me about cattle.
Then, he asked me if I knew that male cattle were lactating at the time of slaughter.
No. I did not.
He said the number was somewhere around 20 percent.
I love a good conspiracy theory, but I also raise cattle, and this sounded completely absurd. A steer is a castrated male bovine. A steer does not get pregnant. A steer does not have a calf. A steer does not produce milk.
At least, that is what I thought.
The man texted me a photograph of a research poster he had seen at a food conference. I immediately sent it to my God, Guns and Beef text thread, as well as to my father and stepmother, who have a small dairy in Idaho.
The God, Guns and Beef thread lit up. Wow. That’s astonishing. That’s concerning.
My father didn’t even believe it was true. My stepmother responded, “That’s crazy.”
I was with them. Surely, there was something we were misunderstanding.
I searched the internet for the poster and found the complete research. I honestly couldn’t believe what I was reading. I kept thinking there had to be an explanation I was missing. Maybe “lactating” meant something different in this context. Maybe they were talking about cows that had previously calved. Maybe the photograph was misleading. Something.
But no.
These were heifers and steers. And some of the steers were producing actual milk.
Researchers from West Texas A&M University, along with a researcher from Cargill Protein, had examined 20,481 finished cattle originating from 33 feedlots. Their poster had a rather appropriate title: “Outcomes of Unintended Consequences: Frequency of Lactation and Intact Males and Their Impact in Finished Cattle.”
They found 6,078 lactating animals.
Before I give you the breakdown, a little cattle terminology is necessary. A heifer is a female bovine that has never given birth. So it is strange for a heifer that has never had a calf to be lactating. But a steer is a castrated male. A steer producing milk takes strange to another level.
Among native beef heifers, 28.77 percent were lactating. Among dairy-cross heifers, an astonishing 55.81 percent were lactating.
Among native steers, 14.55 percent were lactating. Among dairy-cross steers, 19.66 percent were lactating.
I stared at those numbers.
I’ve raised cattle for years, and if someone had told me that afternoon that researchers were finding milk coming from roughly one out of every six finished steers, I would have thought they were repeating something they saw on the internet that wasn’t true.
Except now I was looking at the research myself.
I couldn’t stop thinking about it. I had just finished speaking at the Theodore Roosevelt Presidential Library. I was in one of the most beautiful places I had ever visited, and instead of enjoying the rest of my evening, I went back to my hotel and started searching scientific papers about lactating male cattle.
I raise grass-fed beef. We feed some grain to our dairy cows, but we do not use hormonal growth implants. I have never seen a steer lactate. Not once. I have never seen a heifer lactate unless she was approaching the birth of a calf.
That is anecdotal. I understand the difference between my experience and a controlled scientific experiment. But my experience certainly gave me a hypothesis.
I think it’s the implants.
But I don’t want to think it’s the implants.
I want to know.
Hormonal growth implants are ubiquitous in conventional American feedlots. U.S. Department of Agriculture data have found that roughly 90 percent of feedlot steers and heifers receive at least one growth-promoting implant between placement and marketing.
The Cargill-affiliated study did not give the individual implant histories of these animals. Therefore, I cannot tell you that 90 percent of these particular cattle were implanted, nor can I tell you that implants caused their lactation.
But the mathematics matter. If these 33 feedlots resembled the conventional feedlot industry as a whole, we would statistically expect the overwhelming majority of these cattle to have received implants.
And these aren’t substances that simply make cattle hungrier.
Growth-promoting cattle implants can contain compounds including estradiol, zeranol, and trenbolone acetate. They intentionally manipulate endocrine pathways because doing so increases growth and improves feed efficiency.
Then, I discovered something that moved me from disbelief toward genuine concern.
Scientists have known for decades that you can make a bovine lactate without pregnancy by manipulating its hormones.
Beginning at least in the 1970s, researchers experimented with inducing lactation in nonpregnant cattle. Estradiol and progesterone were among the hormones used in those protocols. Researchers subsequently demonstrated that lactation could even be hormonally induced in heifers that had never calved.
To be clear, the protocols used to induce lactation experimentally are not identical to commercial beef implants. That distinction matters.
But there is overlap in the hormonal pathways and even in the compounds involved. Estradiol, for example, appears in experimental lactation-induction research and is also used in approved cattle growth implants.
Even more directly, researchers conducted a controlled study in 1991 on never-calved beef heifers receiving growth-promoting compounds including estradiol, trenbolone acetate, and zeranol. Some of the estrogenic treatments caused measurable changes in mammary development compared with untreated controls.
This was the point at which my disbelief began to turn into concern. I had begun this research trying to figure out why the poster couldn’t possibly mean what I thought it meant. Instead, every paper I found made the biological possibility less absurd.
None of this proves my hypothesis.
But it certainly makes the hypothesis worth testing.
The researchers behind the recent slaughter study offered another possible mechanism. Their poster notes that excess body fat can increase estrogen production and suggests this could contribute to galactorrhea—milk production unrelated to normal pregnancy and birth.
Maybe they’re right. Maybe it’s the implants. Maybe it’s body fat. Maybe it’s diet. Maybe genetics help explain why dairy-cross cattle had dramatically higher rates. Maybe several of these things interact.
But something in the biological environment of these cattle is telling the mammary glands of castrated males to produce milk.
I want to know what it is.
And I don’t think it is too far a bridge to ask what this means beyond cattle.
Human beings also live in an increasingly complicated endocrine environment. We worry about endocrine-disrupting chemicals in plastics, water, cosmetics, and food. We are exposed to substances that can interact with hormonal systems. Meanwhile, in our food system, we intentionally manipulate animals’ endocrine systems to make them grow more efficiently.
I am not claiming that whatever is making these steers lactate is causing a particular health problem in humans. We don’t have evidence for that.
But if something in the environment or in the management of our food animals is producing an endocrine effect dramatic enough to make castrated males lactate, I want to understand what that something is. Then, I want to know whether it has downstream consequences for the animal, the meat, or the people who eat it.
Maybe it doesn’t.
But we should know.
This brings me back to a question I find myself asking repeatedly about our modern food system: What are we trading for efficiency?
Hormonal implants work. That is why the industry uses them. They allow cattle to gain weight faster and convert feed more efficiently. Efficiency helps make beef more affordable and allows more food to be produced using fewer resources. Those are real benefits.
But our beef system has also become extraordinarily consolidated. A handful of enormous meatpackers process the great majority of America’s fed cattle, while standardized feedlot practices reach huge portions of our food supply.
So how long has this been happening?
Were steers lactating at anything approaching these rates in 1950? In 1970? In 1990? Have slaughterhouse workers been seeing this for decades while nobody thought to count it? Or is this a relatively modern phenomenon?
I went looking for those answers too.
I found decades of research showing that hormones can induce lactation without pregnancy. I found research showing that growth-promoting hormonal treatments can affect mammary tissue. I found an enormous body of research devoted to making cattle grow faster.
What I could not find was the experiment I desperately want to see.
Take comparable cattle. Implant half using conventional feedlot protocols. Leave half unimplanted. Feed and finish them under otherwise comparable conditions. At slaughter, demand researchers who don’t know which animals belong to which group determine how many are lactating.
If the unimplanted steers lactate at the same rate, my hypothesis is probably wrong.
Great. Then let’s find out what is causing it.
But if lactation is dramatically more prevalent in implanted cattle, we need to know that too.
I can jump to conclusions. Anyone can. What I can’t understand is why we wouldn’t want the answer.
Twenty-four hours ago, if you had told me that roughly one in six male cattle examined in a large feedlot study was lactating at slaughter, I would have told you I didn’t believe you.
Now, I believe it.
I’m still a little stunned that it’s true.
What I don’t know is why.
And until we understand why castrated male cattle are producing milk, I don’t think we have any business pretending there isn’t a question worth asking.
