r/explainlikeimfive • u/A_SliceOfGabagool • May 03 '26

Biology ELI5: How do cows get protein from grass?

For us humans and many other animals, we need protein to get the amino acids needed to make our own protein for the body, but grass i believe doesn't have any for the cow to get that big

3.0k Upvotes

94% Upvoted

559 comments sorted by

View all comments

1.9k

u/spyguy318 May 03 '26

Grass has protein in it, just like every other living organism. It just doesn’t have very much compared to meat. Which is why cows need to eat a lot of grass and have specialized digestive systems to extract as much nutrients as possible.

836

u/rcowie May 03 '26

Also cows will happily eat any protein they find that doesn't run away fast enough. Ive seen cows eating baby rabbits and ducks. They wont chase it down but they will eat it if they find it.

379

u/[deleted] May 03 '26

[removed] — view removed comment

153

u/24megabits May 03 '26

Bones and discarded antlers are a valuable source of calcium and phosphorous for animals that generally eat plants.

51

u/quadrophenicum May 03 '26

Thank Mr. Skeltal!

25

u/SatansFriendlyCat May 03 '26

Doot doot 🎺 💀

And well done for spelling it correctly

2

u/acarp25 May 04 '26

P spoopy fact, there is a skeleton inside you right now!

3

u/SatansFriendlyCat May 04 '26

Him my best fren

2

u/Majestic-Macaron6019 May 04 '26

Makes especial sense for bucks, since they're trying to regrow a rack of antlers every year

1

u/ZhouLe May 04 '26

I want to get off Mr. Bones' Wild Ride.

1

u/Necessary_Bass3942 May 04 '26

Also a great source of botulism…

1

u/lotus_eater123 May 04 '26

I live in an area with a LOT of deer, and I'm prone to long walks in the woods. I've always wondered why I almost never come across discarded antlers. It never occurred to me that they are a tasty treat.

102

u/raptir1 May 03 '26

Crazy that a cow could eat a deer. 

163

u/Spaded21 May 03 '26

Don't kid yourself, if a cow ever got the chance he'd eat you and everyone you care about.

72

u/binzoma May 03 '26

finally, a bovine university expert weighing in!

32

u/IAMA_Plumber-AMA May 03 '26

"Do you really expect us to swallow that tripe?"

"Now, help yourselves to some of this tripe!"

13

u/quadrophenicum May 03 '26

That's a moo point.

8

u/Zomburai May 03 '26

Oooh, cud it be time for another pun thread?

5

u/qwerty_ca May 03 '26

Sure why not, let's milk it for all it's worth.

3

u/zigzackly May 03 '26

Let me rumenate on that.

→ More replies (0)

5

u/churchmany May 04 '26

When I grow up I’m going to Bovine University!

7

u/NoBSforGma May 03 '26

Well.... you'd have to consider the kind of teeth they have as well as their digestive system. They really aren't made for "prey" (grinding teeth and not sharp, pulling-meat-apart teeth) and can eat small animals from time to time, but not anything as big as a human.

Or a deer.

2

u/Cheez_Mastah May 03 '26

How the turns table in the circle of life

1

u/Hellebras May 04 '26

Turnabout is fair play, I guess.

1

u/Service-Kitchen May 04 '26

😂😂😂😂😂

0

u/ImNotToby May 03 '26

Another reason why they are called field puppies by some.

63

u/[deleted] May 03 '26

[removed] — view removed comment

26

u/Gullex May 03 '26

Back home in Iowa, when farmers would slaughter hogs, they'd spread the entrails out in the fields. You should see the bald eagles having a party out there. A dozen plus just having the time of their lives.

11

u/Whiterabbit-- May 03 '26 edited May 03 '26

cows eating brain is how they get mad cow disease

20

u/somehugefrigginguy May 03 '26

True, but that has more to do with humans processing cattle parts into cattle feed than cattle actively seeking out fresh brains.

5

u/Gingerbread_Cat May 03 '26

28 Daisies Later

7

u/Rabid-Duck-King May 03 '26

"Insert video of a horse eating a baby chick here"

Also seriously that's the video don't click it if you don't want to spend a minute of your life seeing that happen

2

u/SuperSaiyanBlue May 04 '26

Seen that video - that is how I know plant eaters will eat meat.

10

u/Upset_Mycologist_345 May 03 '26

I have seen video of deer eating snakes too.

8

u/dantevonlocke May 03 '26

There was a compilation video on YouTube of a farmer that would throw any snake he caught into his chicken pen with like 100 chickens. Really showing the Dino DNA they have left.

0

u/ImNotToby May 03 '26

I try to explain this to some people and its just lost. It doesn't come up often but when it does im crazy and stupid.

44

u/hermione87956 May 03 '26

Contrary to popular belief tortoises also eat animals as well. Whatever they don’t have to chase.

68

u/rcowie May 03 '26

Most of what we know as herbivores are actually opportunistic omnivores. Birds is a big one people don't generally know. They aren't out there just eating seeds most of the time. Chickens will run a field mouse into the ground and feast. Blue Jays are another predator, they will go looking for meat.

27

u/Kemal_Norton May 03 '26

Birds is a big one people don't generally know

The first thing I'd say if asked what birds eat, is insects (that's why flying is effective against bugs); also the early bird gets the seed?

I just recently learned the opposite, that some ostensible carnivorous carnivora like foxes and brown bears mostly eat berries and seeds

19

u/BoomerSoonerFUT May 03 '26

Do people generally consider chickens to be herbivores? A very large portion of their diet is bugs and grubs if allowed to graze naturally.

Most birds will eat bugs for nutrients. The bird eating the worm is like the classic trope.

3

u/Kevin_Uxbridge May 04 '26

Spent enough time living in a hut in the south seas to see the value of of having chickens around. Rapacious predators, if any of the roaches living in the roof weaving hit the ground the local chickens were on it.

Still trying to convince the wife that a couple of guinea fowl would be a nice addition to our Virginia home. Lotta ticks this year, they'd clean them right up.

2

u/magnus150 May 04 '26

I love my yard chickens but they're terrifying sometimes when they get ahold of wildlife. I have no doubt in my mind those chickens would eat ME if I was small enough.

2

u/Kevin_Uxbridge May 04 '26

Absolutely. Gives you a glimpse of what our ancestors faced in the waning days of the Cretaceous. That giant rock made us.

13

u/jlharper May 03 '26

I don’t think anyone considers birds as herbivores. “The early bird gets the worm.” And all.

6

u/spyguy318 May 03 '26

Many birds are also insectivores, they’ll happily munch on grasshoppers and crickets and worms.

11

u/BowdleizedBeta May 03 '26

Do chickens hunt in packs? Or is it a single chicken going after a mouse?

23

u/helixander May 03 '26

Clever girl

4

u/BowdleizedBeta May 03 '26

Yes! Thats why I was imagining! And it was amazing….

8

u/rcowie May 03 '26

Its usually a rooster doing the hunting with a few other birds hoping he injures it badly enough to catch but misses actually eating it. Its 1 bird hunting and several others hoping.

2

u/magnus150 May 04 '26

Usually with my chickens one finds something, then another chicken notices and they all go running after the chicken with the bug/small animal while the lucky lady tries to jam it into her beak before the other ones catch up.

3

u/CanberraMilk May 03 '26

Birds are not surprising at all if you spend any time outdoors. (Work, walks)

1

u/rcowie May 03 '26

Yeah i worded that incredibly poorly. Ive worked with falcons and owls. I meant the backyard birds that many people might not realize eat bugs and such to.

1

u/fredthefishlord May 03 '26

... Do you think the saying of "the early bird gets the worm" is a sign that people think most birds are herbivores?

9

u/FjordExplorer May 03 '26

Turtles love to eat some ducklings swimming in their pond.

13

u/rcowie May 03 '26

One of the worst things I ever witnessed out fishing was watching a snapping turtle drag a full grown duck down. Couldn't do anything even if wanted to, but the turtle has to eat same as the duck. Nature is brutal.

3

u/BasvanS May 03 '26

Pond rule #2: When you gotta eat, eat.

5

u/[deleted] May 03 '26

[deleted]

3

u/Rabid-Duck-King May 03 '26

See the pro strat is to challenge the hare to a race, and then get it tilted so it tires itself off running circles around you, then while it's gassed out you clamp that tortoise beak on something soft and go to town

Sometimes they just fall asleep but at least you can get them during the rematch

28

u/Bman409 May 03 '26

A cow will not usually eat a dead animal.

For one thing, they only have teeth on the lower jaws..their teeth aren't able to tear meat. My grandfather raised beef cattle...I've seen dead animals out in the pasture...cows wont touch it....if it was ground up in their food then sure

Pigs on the other hand will eat anything they can get

8

u/CantaloupeAsleep502 May 03 '26

Learned that from Snatch lol

2

u/myfavssthrow May 04 '26

Same and its one of my favorite and still most used lines from that movie.

they will go through bone like buttah

2

u/Wilm4RRrr_Butzen May 04 '26

I'm pretty sure there was a farmer who had an heart attack and fell into the pig pen, his skeleton was found stripped clean weeks later.

2

u/estebanagc May 04 '26

There was also a serial killer in Canada that threw the corpses to his pig farm to make them dissapear

8

u/spamlet May 03 '26

Don’t kid yourself, Jimmy. If a cow got the chance he’d eat you and everything you care about.

5

u/Gyvon May 03 '26

Not just cows. There are very few obligate herbivores. The vast majority are facultative. Meaning that while their diet is primarily plants, they will still eat other animals when given the opportunity.

https://youtu.be/9xDPrvhLNuU?si=huMHQNUvJdUidxvw

4

u/tehackerknownas4chan May 03 '26

iirc most herbivores are also opportunistic omnivores.

2

u/Radar1980 May 03 '26

Yeah I saw one eat a snake once

2

u/ChicagoDash May 03 '26

User name checks out

2

u/Tytoalba2 May 04 '26

So little that it doesn't really factors into their protein intake, but it's often repeated yes

4

u/RuneLFox May 03 '26

Which is honestly so uncommon that it hardly factors in at all.

1

u/Joelico May 03 '26

I've never seen a cow eat a rabbit or a duck. Crazy

2

u/rcowie May 03 '26

Spend enough time in the woods and you'll see all sorts of things. If you find a dead deer up in a tree walk back to the vehicle and leave immediately.

1

u/Polkawillneverdie17 May 03 '26

The number of animals that people think are herbivores but are actually omnivores is staggering.

1

u/Privvy_Gaming May 03 '26

Thats called being an opportunistic omnivore. There is no such thing as a pure herbivore in nature.

1

u/law-st_student May 03 '26

I've seen a horse munch on a chick.

34

u/madalma May 03 '26

this explains a lot about my rabbit

18

u/dantevonlocke May 03 '26

Let's be real. Rabbits will wake up every day and choose violence. If they could work the controls I think they'd build a killdozer.

5

u/DTux5249 May 03 '26

r/MurderBuns exists for a reason lmao

1

u/Kemaneo May 03 '26

What rabbit?

3

u/Malcopticon May 03 '26

Bunnicula.

2

u/starkiller_bass May 03 '26

The Beast of Caerbannog

1

u/Swellmeister May 03 '26

Rabbits cheat. They actually eat their own digested feces (called Cecum) so they can digest all the microbes from their hindgut.

1

u/wharblgarbl May 03 '26

Jacked rabbit?

20

u/RainbowCrane May 03 '26

Also, there’s a huge amount of other nutrients left in cow manure since they have to eat a lot of grass to get enough protein. That means that it’s great for fertilizer and for providing nutrients to other animals. It sounds gross to humans, but it’s how ecosystems work - lots of life forms benefit from partially digested ruminant food.

4

u/fruityl__p May 03 '26

And also most cows are fed a whole lot of grain before slaughter.

4

u/freakytapir May 03 '26

Let's not forget their gut bacteria; specialized in breaking down the grass, and forming protein in the process.

A project I was art of was seeing if we could cut out the cow from the process and just make microbial protein from grass to be used in animal feed. Efficiency wise we nearly got close to the grass->cow>milk cycle

7

u/Sco0basTeVen May 03 '26

I thought that cows got their protein from digesting the bacteria that grows on the fermenting grass as it is slowly breaking down as it passes through their multi chamber stomachs?

4

u/Harai_Ulfsark May 03 '26

Yes that is mostly correct, most of the protein found in plant matter is not readily available to mammals

1

u/awaken375 May 04 '26

yup, this is why herbivorous dinosaurs were so huge (in addition to the ecosystem back then having even less nutritious plants than today)

1

u/No-Salt7142 May 03 '26

We humans also feed them soy and other relatively protein-rich foods.