By Rob Diepersloot, Dairy Farmer and Founder of WonderCow
When a supplement company says their colostrum is 100% grass-fed and sourced in the United States, it sounds simple. Clean. Trustworthy.
But if you’ve worked in the dairy industry your whole life, you know it’s not that simple.
This isn’t about attacking anyone. It’s about explaining a supply chain reality that most people never get to see. In most supplement supply chains, brands don’t buy directly from farms. They buy from brokers, who buy from manufacturers, who buy from aggregators. And unless there’s real chain-of-custody documentation, the story can get fuzzy fast.
As a dairy farmer, I know how colostrum is collected, moved, and processed. In fact, I have personally collected it, moved it, and processed it myself. And I’ve learned there’s a lot of gray area around “grass-fed” language, especially in supplements. Consumers deserve clarity on what these terms actually mean, what requires proof, and what doesn’t.
What I’ve found is that many consumers assume “grass-fed” means “no grain ever.” But the truth is that this is not always the case.
A U.S. sourced, 100% grass-fed colostrum at national supplement scale is extremely difficult no matter what they say on the label. Unless a brand can show unusually strong documentation and certifications to prove it, you should probably ask them a series of questions.
Let’s dive in.
What does “grass-fed” mean vs. “100% grass-fed”?
Before we talk supply, we need to get the wording right, because these terms get mixed together constantly.
- Grass-fed is a diet claim. It refers to what cows eat, but the strictness of the claim can vary unless it’s tied to a published standard, certification, or audit trail. (1)
- 100% grass-fed is a stricter diet claim: no grain, no concentrates. If it’s not certified (or independently audited), it’s still just a claim. (2)
Two common programs that publish grass-fed standards are American Grassfed Association (AGA) and Certified Grassfed by A Greener World (AGW). (2)
The point is not that one term is “good” and another is “bad.” The point is that these words mean very different things, and in supplements, you should expect proof if a company is building their whole brand around the claim. Unfortunately, what a company includes on their label is not enough proof, since many of the claims do not require verification in the supplement industry.
How does the definition of grass-fed apply to colostrum?
Colostrum is the first pre-milk produced after a cow gives birth.
Calves are born without an established immune system, so they rely on colostrum’s bioactive components to help establish their gut and support early immune function. Because of this, on any responsible dairy, the rule is simple:
The calf comes first.
At WonderCow, that is our calf-first promise.
It’s not marketing. It’s animal care and our responsibility as dairy farmers.
For us, colostrum for supplements comes from what’s left after calves have received what they need, plus what can be responsibly collected, stored, and traced. That’s the starting point for everything else.
Most dairies in the US operate in the same way – they would only be willing to sell the surplus colostrum to a supplement manufacturer after their calves get what they need. Which leads us to ask, do 100% grass-fed dairies provide enough surplus colostrum to provide for supplement companies? Let’s dive into colostrum and milk production on grass-fed dairies.
Do 100% grass-fed dairies provide enough surplus colostrum to provide for supplements?
Let’s check out the facts.
1. Grass-fed dairies are a tiny portion of the U.S. dairy industry
To understand scale, we have to look at the size of the dairy industry in general.
In the U.S. in 2022, there were 24,470 farms that produced and sold milk from cows.(4)
Now compare that to 100% grass-fed supply. Depending on how strictly someone defines “grass-fed,” estimates vary. One USDA NIFA project summary describes the grass-fed dairy sector as estimated to be over 300 farms, and in the same project reporting, the target audience for “organic dairy farms that are currently or transitioning to feeding only grass or legume based feedstocks” is described as approximately 450 farms.(5)
Whether you use 300 or 450, the point is the same: 100% grass-fed dairies make up just about ~1.5% of the U.S. dairy farming industry. (4)
2. Milk output is often lower in grass-fed systems, which lessens surplus
In non-dairyman terms, this translates to: grass-fed cows produce significantly less milk on average, meaning there is also less colostrum produced, often with no excess colostrum to be used for supplements at all.
This part always needs nuance because every farm is different. Breed, forage quality, genetics, and management all matter. But we can still talk about averages.
To start off, traditional forage-and-grain dairy farms do feed their cows grass. A lot of grass. In fact, the majority of their ration, or diet in non-dairyman terms, is forage (grass, alfalfa, and silage). For our farm personally, we have a full-time nutritionist who formulates the cow’s diet based on their lactation, milk production level, body composition, breed, and pregnancy status. A cow will have different energy needs depending on those factors, which will determine the ratio of grass, starch, fats, proteins, vitamins, and minerals the cow should be consuming per day in order to stay healthy while producing colostrum and milk.
Now to milk production: in grass-fed reporting, average milk production per cow is self-reported around 10,599 pounds per cow per year. (6)
Compare that to the U.S. average production per cow, which USDA reported in 2024 as 24,178 pounds. (7)
A grass-fed cow produces 58% less milk than the average dairy cow in the U.S. That’s a big gap. And in a colostrum conversation, here’s why it matters:
When overall production is lower, it often means there’s less “extra” capacity and less consistent surplus colostrum available for collection, especially when you keep calf-first care non-negotiable.
So “U.S.-sourced, 100% grass-fed colostrum” should trigger a simple follow-up question:
Is there enough verifiable surplus colostrum to supply all the companies making the claim?
3. Calf-first care makes surplus colostrum the bottleneck
Colostrum yield and quality vary a lot by cow. But what doesn’t vary is this: the newborn calf needs a meaningful volume quickly.
Common dairy guidance is to feed large-breed calves about 4 quarts of colostrum within one hour of birth (or split into two feedings within that first hour), with additional colostrum feeding soon after (often within the first 6 to 12 hours). (8)
That’s why “calf-first” isn’t a slogan.
It’s standard care.
Here’s the bottleneck nobody wants to talk about:
If you’re sourcing from a small number of grass-only herds, and you’re doing calf-first correctly:
How much consistent, traceable surplus is actually left for supplements?
4. Even if surplus colostrum exists, collection logistics are brutal at scale
Even if surplus existed, you still have to collect it.
The small number of grass-only dairies are spread out geographically. And colostrum collection is time-sensitive. You need tight handling and fast cooling or freezing to protect quality. (9)
When farms are scattered and volumes per farm are small, the time, fuel, labor, and complexity make it extremely hard to collect colostrum at scale in a way that’s consistent, economical, and verifiable.
That’s not a knock on grass-fed dairies. It’s simply what happens when you try to build a supplement ingredient pipeline from a limited number of farms spread across a huge country.
So when a brand claims large-scale, consistent, U.S.-sourced, 100% grass-fed colostrum, the fair question is:
Can you show the sourcing network, the chain-of-custody, and the verification?
5. The “grass-fed” colostrum claim in supplements can mean different things
This is where consumers get confused, and I don’t blame them.
Many shoppers assume “grass-fed” colostrum is tied to one strict, universally enforced definition. In supplements, it is unfortunately not that clean.
Companies still have to be truthful in labeling and advertising. But if a brand isn’t tying “grass-fed” to a published standard, certification, or audit trail, they are relatively free to include the term “grass-fed” and consumers are left guessing what exactly they mean by it.(1)
That’s why I come back to one simple standard:
If you’re going to use the claim, define it and prove it.
What to ask any brand (including WonderCow):
- What do you mean by grass-fed? Forage only, or forage-forward?
- Is your grass-fed claim certified or audited? Which program?
- Is your colostrum U.S.-sourced? From what region?
- What are your collection, freezing, and storage practices?
- What testing do you do on the finished product?
- Can you explain chain-of-custody from farm to finished powder?
A trustworthy brand won’t be annoyed by these questions. They’ll welcome them.
Summing Up the 100% Grass-Fed Question
Here’s the context most people never get:
- The bulk of what a traditional forage-and-grain dairy cow eats is grass; a dedicated nutritionist recommends silage, starches, fat, protein, vitamins, and minerals in addition to grass in order to meet the cows energy demand.
- Grass-fed dairies make up just ~1.5% of the US dairy industry
- On average, 100% grass-fed cows produce less than half the milk of traditional forage-and-grain dairy cows.
- Regulatory bodies do not monitor these grass-fed claims closely in the supplement industry so brands do not have to prove that their cows eat exclusively grass in order to include “grass-fed” on their label
When you combine a small supplier pool with calf-first reality, then layer in logistics, economics, and the efficiency of collecting colostrum...
You can see why large-scale “U.S.-sourced, 100% grass-fed colostrum” is a claim that demands unusually strong documentation and should be questioned.
And here’s the part I want to be honest about.
When we launched WonderCow, we went looking for a grass-fed source for the consumers who make this a priority. We wanted it to be real. We wanted it to be verified. We wanted it to be something I could stand behind truthfully as a dairy farmer.
But in the end, we could not find a legit U.S. grass-fed colostrum source that checked the boxes the way it needed to in order to make that claim responsibly, especially when it came to credible certifications and a clean audit trail.
So as 7th generation dairy farmers, we made a decision and chose not to make the claim.
Not because it sounds bad. Not because grass-fed systems dairy farms don’t exist. But because we know the truth behind how the colostrum industry works. We’re connected to it. We live and breathe it every day.
And to be honest, this decision has put us at a disadvantage in so many ways. It is easier to sell a buzzword than it is to sell the truth, especially when other brands use the claim loosely.
But knowing the truth, it’s the right thing to do.
We’re here to be transparent and educate consumers as much as we can.
We guarantee the best colostrum product available. Whole. Pure. Ethically and sustainably sourced from U.S. farms and kept as natural as possible.
No hype. No shortcuts.
Just the real thing, from people who actually do this for a living.
With gratitude,
Rob Diepersloot
Founder, WonderCow Nutrition
Sources
(1) Organic Valley: 8 Things You Should Know About Grass-Fed Dairy
(2) American Grass-fed Association (AGA). AGA Grassfed Dairy Standards (adopted 8/24).
(3) A Greener World (AGW). Certified Grassfed by AGW.
(4) Dairy Cattle and Milk Production. ACH22-16/September 2024
(5) Advancing Grass-fed Dairy. National Institute of Food and Agriculture
(6) Grass-fed Dairy Production Practices and Farmer Perceptions. 2024 GF Survey Results Article
(7) Milk Production. National Agricultural Statistics Service (NASS) 02/2025
(8) Penn State Extension. Feeding the Newborn Dairy Calf.
(9) Feeding the Newborn Calf. Dairy Cattle Extensive.