What is the environmental impact of dairy? To answer this question, I talked with experts in the dairy industry to learn more about dairy sustainability. This is Part Two of my Dive Into Dairy series!
This is part of a four-part series written in partnership with Midwest Dairy. Stay tuned for the rest of the posts in the series where we will explore where dairy comes from and how dairy plays a role in sustainability! Check out Part One for more on dairy nutrition.

Does this view look like what you imagine when you hear the words “dairy farm”? Granted, there aren’t any cows pictured here but if you keep reading, you’ll see some soon!
This was taken on one of my last pre-COVID farm tours, on a dairy farm outside of Higginsville, MO. I had the unique opportunity to visit with the Heins family (Chris, Adriane, and their young kids) and take a deep dive into the inner workings of a dairy farm. I learned a ton that day, but it dawned on me that I never spilled the full story here on the Street Smart Nutrition blog.
So let’s do it!
Dairy Sustainability: What Does That Mean?
The word “sustainability” is similar to the word “healthy” in that it can have significantly different meanings depending on who you ask. In some cases, people are talking about environmental sustainability. Other times, it’s a focus on financial sustainability. There’s also the human factor – farmers, like everyone else – have to contend with the limitations on their time and energy. What does sustainability look like through that lens?
To tackle this complex topic, I spoke with a leading expert in dairy sustainability to gather his insights on the environmental impact of dairy. Dr. Juan Tricarico is an animal scientist based near Chicago, IL. He is currently serving as the Vice President of Sustainability Research at Dairy Management, Inc (DMI). He’s dedicated his career to researching ruminant nutrition in beef and dairy cattle. With ten years of experience with DMI, along with more than 50 publications, it’s easy to see why he’s considered one of the foremost experts on this topic.
What is “sustainability”?
When the word “sustainability” is used in the context of agriculture or the food system, it’s typically used in the environmental sense. Dr. Tricarico confirmed this, adding that although there is an emphasis on environmental impact, “the goal is sustainable milk production.” That is, for the dairy industry to produce milk for dairy foods for the public in the manner that’s most respectful to the resources, the land, the animals, and the people involved.
Because much of his research investigates the role of animal feed for ruminants (particularly beef and dairy cattle), he’s uniquely qualified to offer a glimpse into the broader context of what that environmental emphasis looks like. But first, we need to better understand what makes a ruminant animal and their digestion different from, say, a human.
Take a little detour with me to learn more about how these key differences in our guts play a role in dairy sustainability.
How is ruminant digestion different than human digestion?
Humans and some other animals have a simple, or monogastric, digestive system. It’s pretty straightforward: food goes in, and for the most part, it only moves in one direction until it’s excreted out the other end.
Cattle and other animals like goats and sheep are different. They have a four-chambered stomach that allows them to digest plants and plant byproducts that are indigestible to humans. In order to withdraw energy and nutrients from these plants and plant byproducts, they need more room in their stomachs. And ruminant animals have a LOT of room. In cattle, the rumen (first chamber) can hold up to 50 gallons of digested feed material!
Here are some other key differences between ruminant and human digestion:
One of the most interesting things I learned about the rumen (and ruminant animals) has to do with fermentation. The rumen is anaerobic, meaning there is no oxygen in there. That allows fermentation to take place, transitioning an otherwise low-quality protein like what’s found in grass, into a higher-quality protein that is either used by the cow’s body (for many of the same functions as protein in the human body) or in the milk she produces. When a dairy cow is chewing her cud, seemingly very relaxed, she’s actually working very hard to further breakdown those plant materials in her feed to support this fermentation process. Ruminant animals can regurgitate boluses of food multiple times until it reaches the optimal composition for them to continue digesting and fermenting it in the other stomach chambers.
This fermentation can’t happen without the support of fungi, bacteria, and protozoa in the dairy cow’s GI tract. They play a similar role as the bacteria that make up the human microbiome. And, just like with humans, a byproduct of all that fermentation is (you guessed it!) gas. The key difference here is that instead of working its way down and out, dairy cows and other ruminant animals release gas through belching.
So what does that have to do with sustainability?
Now that we’ve had our crash course in ruminant digestion, we can get to the good stuff!
Sustainability encompasses all the inputs that go into producing high-quality dairy products. Since feed is the #1 input that goes through a dairy cow’s system, it stands to reason that much of the focus is placed here.
According to Dr. Tricarico, “the number one thing farmers can do to improve sustainability is to feed [their cows] a balanced diet.” When I heard this, I got excited because I saw a really clear parallel to my work and interest in human nutrition. Just like I make sure to always remind people that one meal or snack doesn’t make or break a healthful diet. The big picture is more important for dairy sustainability. In order for a dairy cow to produce milk in a way that’s healthy and sustainable for her, she needs the optimal balance of nutrients and energy.

What do dairy cows eat?
Just as no single food can provide 100% of the necessary nutrition for people, no single feed ingredient can provide 100% of the necessary nutrition for dairy cows. Here in the United States, dairy farmers include a lot of corn silage in their feed rations. Silage is made from more than just the corn kernels – it also uses the stalks, cobs, and leaves from the corn plant. Dairy farmers also feed a lot of alfalfa hay, which is actually not a grass but rather a legume.
Think of it this way: we tend to make as few trips to the grocery store as we can. We rely on packaged foods with a longer shelf-life to feed ourselves and our families. Well, dairy farmers are doing the same thing when they turn to silage and hay when they’re feeding cattle. They are both a method of preserving fresh feed to use later. Making silage is like pickling and making hay is like dehydrating; both extend the “shelf life” and allow farmers to store enough feed to nourish their herd.
In addition to these core components, feed rations might also include other ingredients, like concentrated sources of specific nutrients or minerals, ground corn kernels, distillers grains, wheat mince (a byproduct of creating flour), or other plant byproducts from various industries. Again, the ruminant digestive system is an amazing thing because almost all of these ingredients would offer little to no nutrition value for humans. In fact, most of them wouldn’t even be considered edible to us!

How can dairy farmers improve sustainability?
While there are many aspects to a truly “sustainable” dairy operation, we are focusing on feed efficiency in this post. Feed efficiency is an indicator of how efficiently an animal, like a cow, can convert feed rations into the desired output. In the case of dairy sustainability, we’re looking at how efficiently a dairy cow can convert feed and water into milk. In speaking with Dr. Tricarico, it dawned on me that for a dairy cow’s diet, the whole is greater than the sum of its parts. The way he explained it, certain combinations of feed can lead to greater feed efficiency because when specific ingredients are combined in precise, measurable ways, the digestibility of the entire diet improves.
In addition to dialing in the feed efficiency of what is fed to dairy cows, there are also opportunities to use genetics to drive improvements for dairy sustainability. While most of us likely picture the quintessential black and white Holstein cow when we hear “dairy cow” there are actually many breeds with unique characteristics. Dairy farmers are able to select for certain traits they want. Feed efficiency is one phenotype a farmer may select for, but they may also want a herd that is more resistant to disease or more tolerant of a hot, humid climate.

Changes in genetics can feel slower than other changes. So dairy farmers can also focus on other aspects of sustainability like animal care, waste management, and water conservation. When it comes to emissions, methane is often a hot (pun intended) topic around climate change.
I encourage you to check out this post on methane emissions from cattle to learn more about that.
But methane is not the only greenhouse gas (GHG) that poses concerns. Nitrous oxide is another significant factor, especially in agriculture. It’s emitted from the soil and when various fertilizers or pest control products are applied, it can be released into the atmosphere or water. What I found most interesting about cattle and ruminant digestion is that when you improve the feed efficiency, you’re essentially improving the pathways for nitrogen metabolism. This “locks in” nitrogen and diverts it into valuable protein rather than sending it out into the external environment.
When Dr. Tricarico shared some of the figures with me, I was very surprised. I had no idea a dairy cow can potentially source up to 50% of her total protein needs from the nitrogen in her diet. I started to fully understand why he and other dairy sustainability researchers are so dedicated to finding new ways to improve feed efficiency. I inherently knew the two were somehow connected, albeit indirectly in my mind, but after speaking with him I could clearly see the direct connection. Given my background in human nutrition, it was incredibly helpful to see the similarities. I hope you can say the same!
While this is in no way a complete explanation of dairy sustainability, I think we’ll have to wrap it up here. If you’re still reading, thank you for sticking around! These are the types of topics and conversations that are really important to me as a dietitian, but also as just an average person who eats and enjoys dairy foods. I’m naturally curious and I love to learn, but this knowledge is even more impactful when it means I can better understand and appreciate the food on my table.
I always appreciate when farmers, animal scientists, and other experts are willing to talk with me and open this line of communication that I wouldn’t otherwise have access to, so a huge thanks to Midwest Dairy, the Heins family, and Dr. Juan Tricarico for their contributions to this post!
Did you learn anything new? If you’re like me, this may have only generated more questions, so be sure to check out the other posts in my “Dive Into Dairy” series!
If you’re interested in dairy sustainability, you might also be curious about beef sustainability. Click here to learn more about the Beef Sustainability Roundtable with a Kansas Cattle Rancher.