Where do herbivore animals get their protein from?

Is there some way their bodies (cows, horses, rabbits, sheep, deer, elephants, etc.) can synthesize proteins from mere grass and weeds?

 

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Well, many vegetables (say, nuts and seeds) do have protein in them. And keep in mind that grass has a lot of seed in it.

Some grazing animals have enough bacteria in their guts to both break down cellulose AND generate all the vitamins they need, which is pretty impressive. We can't do that.

 

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There's a lot of protein in grass and weeds - if you eat enough grass and weeds. The more obvious question is where the plants get their protein from - that's what the nitrogen is for, in the fertilizer.

Much protein is created by bacteria in the digestion system of many vegetarian animals.

There's also much protein in insects and snails and bacterial or fungal composted detritus and stuff like that, which natural grass and weeds is full of. In commercial feedlots they have taken to supplementing the feed with protein from rendering plants and slaughterhouses to make up for the lack of bugs etc - feeding the waste from slaughtered cattle to other cattle is how the feedlots gave all those people Mad Cow disease a few years ago.

 

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That makes sense. I wonder if grass and its seeds would provide enough protein for humans. Possible solution to world hunger?

 

Sure. Rice and beans, in the proper ratio, will take care of the protein without meat, but if you want to stick to grasses I'm pretty sure you can find something to replace the beans.

What you need is not "protein" in general, but a proper balance of the amino acids your body can't synthesize.

 

Our intestinal flora is not anywhere near as good as a cow's, so we wouldn't get enough nutrition from grass. We also don't have the digestive system that can support the bacteria; a cow's flora need careful pampering to maintain the right pH, oxygen etc levels to be able to break down cellulose. That's why a cow's stomach is so complex, to maintain the complex bacterial mix that can create everything a cow needs - from vitamins to amino acids - from grass.

 

I don't think most herbivores eat just one kind of vegetation. A few, like koalas and pandas are narrowly specialized, but most eat roots, fruit, seed and nuts, as well as different kinds of leaf; in winter, even bark and lichens. Seeds are the richest source of nutrients.

I wonder whether, if we pursue a healthy vegetarian diet, our intestinal flora also change. They must - microorganisms are the most adaptable thing on the planet.

 

They generally eat whatever they can, but they are pretty efficient at generating all their own needs - so they can eat just one grass if that's all they have. In a way cows "make" their own meat - after the bacteria synthesize the lipids, proteins, amino acids etc that they need to survive and reproduce, the bacteria dies and passes down the cow's digestive tract. The cow can then digest and use the dead bacteria themselves as a source of nutrients. Sort of the way we eat yogurt.

Nowadays, of course, cows get fed anything and everything, whatever is cheapest. Feed corn, food manufacturing waste, you name it. Which isn't good for them so farmers often load them up on antibiotics so this unnatural diet doesn't make them sick. The antibiotics kill off some of the bacteria in their digestive system (no surprise, that's what antibiotics are designed to do) which makes it harder for them to create the nutrients they need etc. Which is why the beef you get today isn't much like the beef your grandfather ate.

Absolutely. Intestinal flora eats what you eat; change your diet and they change as well. You're always eating e.coli so they don't even need to adapt; an old strain dies out and a new strain (better adapted to, say, legumes) takes over. They are the main flora but you have all sorts of other bacteria (like lactobacillus acidophilus) floating around in there, and the proportions of the various organisms change as your diet does as well.

 

I had an impression the body can produce some amino acids from sugars . The essential is what our body cannot produce .

 

Maize, rice, wheat, barley, oats, sugar cane, sorghum, millet, rye, teff - - most human food is grass and its seeds.

And grass seeds are higher in protein than most other staple plant foods - cassava, potatoes, various palm and tree fruits not counting nuts, etc - which tend to be high in carbs.

 

Well, outside of sugar cane, what you just listed are all seeds - and generally we can't eat any of them directly. Fortunately we have technology (grinding, baking, malting, cooking, soaking) that can "predigest" such foods for us, to let our less-complex digestive systems use them. Although we still can't digest grass (primarily cellulose) directly, outside of pretty complex industrial cellulosic ethanol processes.

Compare us to the lowly termite who does just fine with nothing but raw wood (and his jaws.)

 

Here the scientist uses CP to refer to crude protein. You can see there is a technical difficulty nailing down exactly how much protein is in a given type of forage under given conditions:

http://www.fao.org/ag/agp/AGPC/doc/Newpub/napier/eastafrica_orodho.htm

 

The available protein in various plant material varies by season as well.

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Young growing herbivore mammals have their early protein needs net by the milk of their mother. As they continue to grow, the percentage of protein they require tapers off. Animals that grow over several years, such as my horses, can be observed to undergo growth spurts that follow the protein curve of the seasonal forage until they reach maturity, with winter being more a time of maintenance. In domestic species, we can influence the rate of growth by supplementing with a protein source year round.

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex4634

(Note: I do not agree with all of the information at this link for the simple reason that horses survived without supplementation prior to domestication.)

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Cattle during winter is fed with corn , so corn must be a provider of proteines or an other way the organism must produce amino acids from starch .

 

I think there is confusion about where and what protein comes from and is. Protein is composed of amines and requires nitrogen, cellulose can't be made into protein (although hemicellulose has some amines) organism must 'fix' nitrogen from air to make protein, only a few types of bacteria are capable of this energy intensive process and I have never heard of them operating in the guts of ungulates. My understanding was that herbivores eat ALOT of plant matter and extract all their fixed nitrogen from that plant matter.

 

Cellulose can't be converted to protein anymore then lead can be converted to gold: Nitrogen must be coming from somewhere and cellulose (with the exception of hemicellulose) has no nitrogen in it what so ever. Now the question is is all this nitrogen coming from plant protein and hemicellulose and other nitrogen containing compounds or are the gut bacteria in ruminants actually fixing nitrogen straight from N2 gas dissolved in the cows digestive track?

First off I don't think that is what I said, second a several hundred pound cow has far more protein in it then you or I do by sheer mass, regardless if its smooth little brain. All the leather and meat and hair of a cow is chalk full of protein or is even pure protein. Brains don't consume much more protein then muscle or skin or bone.