What do your cows eat?

When I talk to my non-farming brothers and sisters about what we feed dairy cows these days, they’re surprised to hear how much science, creativity, and attention to detail are involved in putting that meal together.  We grew up on a small dairy in Wisconsin where the cow’s diet consisted of hay, corn and some type of protein supplement fortified with vitamins and minerals.  The protein source used at that time was largely soybean-based.  Today the types of feeds used are vast and largely consist of byproducts or some type of leftovers from making a human product.  Here are some examples:

Feed Byproduct


Human Product

Soy cakes


Soy sauce

Distillers grains


Ethanol derived from corn

Corn gluten feed


Corn syrup

Whole fuzzy cottonseed


Cotton gin waste

Gummy bears (sugar source)



Sweet corn silage


Canned corn

Here’s a picture of a starch/gummy bear mixture that comes from a candy factory. We feed this to milking cows at a dairy in Minnesota.

The cow’s diet (we call it a ration or TMR short for total mixed ration) is formulated by entering all of our feeds into the computer and balancing for the nutritional requirements of a given group of cows or calves.  There have been mountains of research over the years to determine what levels of nutrients are needed for milk production, gestation, health and growth of animals.  It’s extremely important to me to know that I’ve provided everything that cow needs to remain healthy and productive because, unlike humans she can’t go out when she’s ‘craving’ something to eat.  We watch so many details…when to feed, how much to feed, when to freshen up the feed the list goes on and on.  We even do this thing called a TMR audit and run around the dairy with cameras and stopwatches making sure the feeder is doing everything he can to make the best feed – which seems crazy when I say it like that! 

Here’s a short list of the nutrients that I spend the most time stewing over when balancing a ration.  Fiber – this one is first for a reason; a cow is a ruminant which means she has four stomach compartments and can digest large amounts of fiber.  She has a specific requirement for fiber and if her diet is low she will have digestive upset and can get very sick.  Protein – all animals require protein for function, muscle building and for lactating cows to produce milk.  Energy – this is a tricky one for cows.  There’s a limit to how much of different types of energy we can use or we upset her somewhat-delicate digestive system again.  We use starch, sugar, digestible fiber and fat to meet her high demand for energy.  The reason for the limitation is that inside the rumen, the largest of the stomach compartments, is a very large population of very tiny creatures.  Bacteria and protozoa live in her rumen and essentially, I feed them and they in turn produce energy and protein for the cow.  It’s a crazy symbiotic relationship that can be a little frustrating because if we feed too much fat or oil, the little bugs can die.  Same thing with starch and sugar, we need to offer feeds in the right proportion to keep these friends happy.  Lastly, we spend a lot of time getting the vitamins and minerals correct – balance and proportion is important here too.

A dairy cattle nutritionist’s job is to keep the cows healthy and productive; we prevent illness and help to create contentness.  It’s fulfilling, challenging, ever-changing and rewarding.  From the time I was a little girl feeding hay in the winter, I’ve always loved to watch a cow eat!  You should try it sometime – you might find you like it too.


4 thoughts on “What do your cows eat?

  1. Great job Sarah! My favorite part of watching cows eat when I was little was seeing them stick their tongues in their noses… a very cool trick that dogs also have a knack for. Keep up the good work! Looking forward to reading future posts!

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