Where do herbivore animals get their protein from?

Discussion in 'Biology & Genetics' started by Magical Realist, Jul 29, 2013.

  1. Magical Realist Valued Senior Member

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    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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  3. billvon Valued Senior Member

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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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  5. iceaura Valued Senior Member

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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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  7. Magical Realist Valued Senior Member

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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?
     
  8. iceaura Valued Senior Member

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    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.
     
  9. billvon Valued Senior Member

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    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.
     
  10. Jeeves Valued Senior Member

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    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.
     
  11. billvon Valued Senior Member

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    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.
     
  12. arauca Banned Banned

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

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    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.
     
  14. billvon Valued Senior Member

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    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.)
     
  15. Aqueous Id flat Earth skeptic Valued Senior Member

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    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
     
  16. Fraggle Rocker Staff Member

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    As others have pointed out, the artiodactyls (even-toed ungulates or "hooved mammals": camels, pigs, cattle, sheep, goats, deer, giraffes, antelope, hippopotamus, chevrotains), the perissodactyls (odd-toed ungulates: horses, zebras, asses, tapirs, rhinoceros), and several animals outside of these large taxonomic groups (such as elephants), all have large, complicated digestive systems that maintain a bacterial culture. Many of them have multiple stomachs that send the food back and forth for processing.

    The bacteria have the enzymes to digest cellulose, which is what most edible plant tissue consists of. As they digest the cellulose, they multiply; in other words they are converting the cellulose to protein in the form of more bacteria. The host animal then digests the bacteria, of course leaving enough for the digestive process to continue.

    As noted, there is some protein in plant tissue, specifically the reproductive tissues: nuts, grains, legumes and other kinds of seeds. The protein in nuts, sunflower seeds, etc. is readily digestible. However, the protein in grains and legumes is not. They must be cooked before humans (and other obligate carnivores such as dogs) can digest them and extract the protein for body maintenance--otherwise they pass through us as mere roughage.

    Cattle and other herbivores can digest grains and legumes as easily as they digest leaves and roots: by letting the bacteria in their gut culture do the work.

    Before the invention of the technology of cooking (i.e., the ability to start and control fires) around 2 million years ago, humans (Homo erectus at that time) were obligate carnivores like lions, wolves and weasels. There just aren't enough nuts and sunflower seeds in the ecosystem to provide the protein necessary to support a clan of humans. The ability to cook grains and legumes, and then digest their protein, was a major step forward. Maintenance and operation of the brain requires an immense input of protein, so as our protein intake increased, our brains grew larger. The brain of our species, Homo sapiens, is about twice as large as that of H. erectus.

    Eventually we even learned to cultivate these crops so we had a steady supply of protein in all seasons.

    There are quite a few landmarks in our evolution about which we can say: "That is one of the key events that allowed us to become who we are."

    Cooking is one of them.
     
  17. scheherazade Northern Horse Whisperer Valued Senior Member

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    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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  18. arauca Banned Banned

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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 .
     
  19. Fraggle Rocker Staff Member

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    Domestication has affected the evolution of animals because we practice unnatural selection. Just look at dogs: they have evolved into a separate subspecies, Canis lupus familiaris. They have smaller brains to survive on the lower-protein diet of a scavenger, their teeth have changed shape since they don't have to rip apart their prey anymore, and their instincts have evolved enormously.

    Of course dogs are the oldest domesticated species, because they domesticated themselves--like goats and pigs did a little later, all scavengers attracted to our lovely middens. But there's no reason to suppose that more recently domesticated animals have not also undergone at least slight modification. Diet is one of the main things that changes when an animal stops foraging and is fed by farmers. So it stands to reason that their digestive system might adapt to the change.

    You didn't read my post. I explained that. Cattle are ruminants, with a very long digestive tract full of bacteria. The bacteria turn the starch into protein.

    Besides, corn is a grain, and grain (like all seeds) contains protein. Other well-known grains are rice, wheat and barley.

    But most mammals cannot digest the protein in grains unless it is cooked. So the corn is wasted on the cattle: their digestive system treats it the same way it treats starch. Farmers also feed cows alfalfa, which is a legume and therefore also contains protein. This is also a waste.

    Please read the posts on this discussion more carefully. You're asking questions that have already been answered.
     
  20. ElectricFetus Sanity going, going, gone Valued Senior Member

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    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.
     
  21. Fraggle Rocker Staff Member

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    According to http://www.raising-rabbits.com/carnivore-digestive-system.html, my account is basically correct. The bacteria have the necessary enzymes to digest cellulose, which they convert into protein: their own bodies. These growing bodies divide and reproduce into more bodies, and the herbivores digest the excess population in order to satisfy their own protein requirements.

    Presumably, you are right about the huge ruminant digestive tract being full of nitrogen. Since ruminants don't have large brains their protein requirements are small compared to ours, so the balance of nitrogen, cellulose and bacteria is apparently adequate.

     
  22. ElectricFetus Sanity going, going, gone Valued Senior Member

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    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.
     
  23. Fraggle Rocker Staff Member

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    The only significant quantity of amino acids in plant tissue are in the seeds, which comprise a tiny portion of the plant, as well as being (usually) seasonal. Herbivores are not getting a useful amount of nitrogen directly from the plants.

    It has to be the bacteria that are doing this, so the question remains: Where do they get the nitrogen?

    That's not what I've read. It's the maintenance and operation of the brain that accounts for a large portion of our protein intake. Ancestral hominid species became obligate carnivores when their brains grew too large for the typical primate's herbivorous diet augmented by occasional arthropods and other tiny animals. Fortunately the larger brain gave them the ability to invent the hunting tools needed by an obligate carnivore with no fangs or claws.

    The most striking anatomical change in dogs, as they evolved into a distinct subspecies of wolf, is the shrinkage of the brain to accommodate the lower-protein diet of a scavenger.
     

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