Interesting . Even grass will have varying nutrient concentration depending upon the status of soil fertility , Alka. Eating grass by human being, though looks imaginary , but grass will most of the essential nutrients , however the bigger question is , whether or not , it will suffice the human needs for different nutrients in optimum concentration...

Ya... even cow is such a big creature. I wonder how only grass suffice its needs.

Grass has proteins, essential lipids, nucleotides, minerals, vitamins,.... And cellulose... Cows thanks to the bacterias of the bowell can digest cellulose and obtain glucose...

Cows are ruminants not mongastric animals. They get many of their required nutrients from the various organisms in the rumen.

Grass also exist in varieties with different nutritional contents. By depending on grass alone as well as feeding on variety of grasses, Cows get the needed nutrients for growth, development and for other requirements.

Thank you so much everyone for answering this.

Food of herbivores is in general nutrient poor. However, they have evolved methods for obtaining essential nutrients from their nutrient poor food.They get some minerals from the soil on which they graze. The food a cow ingests first enters a specialized four chambered organ. The first two chambers of this organ function as a fermentation vat. The microorganisms in them breakdown cellulose of the plant cell wall. The process releases contents of the cell which would be otherwise inaccessible to the bovine enzyme. The microbial fermentation produces short chain fatty acid that cows absorb and uses as source of carbon for synthesis of organic compounds. The microorganisms synthesize amino acids for protein for their need from non-protein nitrogen present in the cow's food. The fourth chamber of the organ is like our stomach, which secrets hydrochloric acid and proteolytic enzymes. The microbial mass is killed and digested here. The cows get a substantial amount of amino acids and micro-nutrients from the digested microorganisms. People in this subcontinent learned long ago that feeding oil-cakes makes cow healthier. This is due to high nitrogen content of oil cakes. Some also use measured amount of fermented urea with oil cakes to further increase nitrogen content.

Green grass contain all the essential nutrients for cow.

THE COW IS A RUMINANT (ANIMAL WITH MULTI-CHAMBER STOMACH.....THAT INCLUDES THE RUMEN AND IS ABLE TO CHEW GRASS IN THE MOUTH SWALLOWS IT TO THE STOMACH ...THIS WORKS AS A FERMENTATION CHAMBER) THUS IS ABLE TO PROCESS PLANT CELL WALLS LIKE CELLULOSE IN VARIOUS FORMS GENERATING A FULL RANGE OF NUTRIENTS FOR GROWTH AND MAINTENANCE . THE COW HAS ITS OWN FERMENTATION CHAMBER PROVIDING BASIC KEY NUTRIENTS FOR THE COW AND THE MILK IT PRODUCES (LACTOSE, CASEIN AND OTHER PROTEINS ) TO SECURE HEALTH OF THE OFFSPRINGS. AS AN MD PHD WITH PEDIATRICS AND NEONATAL CLINICAL TRAINING AND A PHD DEGREE FROM MIT FOCUSING ON AMINO ACIDS AND PROTEIN METABOLISM DURING THE SCRIMSHAW/MUNRO/YOUNG YEARS WHICH ENDED IN THE mid/late 90s; WE NEED TO BE MINDFUL THAT BIOLOGY-NUTRITION FOR HUMAN HEALTH IS CONDITIONED BY THE EVOLUTIONARY STAGE OF THE RESPECTIVE ANIMAL SPECIES . MAMMALS AS THE NAME IMPLIES ARE DEPENDENT ON MILK AS KEY FOOD IN EARLY LIFE ; THUS THE COMPOSITION OF HUMAN MILK IS CRITICAL AS A SOURCE OF NUTRIENTS INCLUDING THE RIGHT MIX AND AMOUNT OF AMINO ACIDS (essential and non-essential)/ MINERALS (Ca & P) TO SUPPORT GROWTH AND DEVELOPMENT . HUMAN MILK IS UNIQUE IN PROVIDING THE RIGHT AMOUNT AND TYPE OF NUTRIENTS TO SUPPORT GROWTH AND DEVELOPMENT SPECIFIC TO EACH SPECIE. THE NEED FOR ESSENTIAL LONG CHAIN FATS (N-3 AND N-6 PUFAs) for humans in early life is very high and is sustained for most of the first year of life by human milk, the amount and type of fat in the various mammalian species is defined by the maternal diet and the offspring's weight gain (adjusted for changes in body composition during early growth and rate of subsequent growth at various stages of development. As a short answer to A. Karan see above comment green grass alone can not support the PROTEIN NEEDS FOR growth of large mammals. It is only an ingredient for the biomass generated from grass in the multi chamber DIGESTIVE SYSTEM that provides the energy substrates for fat in milk, and the amino acids/proteins formed by the cow . So with full respect to the the evolutionary process as pointed out by RAHMAN (see above) the cow and thus we humans are dependent on the microbiomes in herbivores /rumminants and the magic of fermentation to deliver milk with specie-specific composition of Proteins (amino-acids) and fats including not only triglycerides and fatty acids but also long chain essential (n-6 and n-3 LCPUFAs including arachidonic and docosahexaenoic acids) fats produced by the microbiome which in the case of ruminants provides good protein including essential amino acids to meet the needs imposed by rapid body growth but is clearly insufficient to provide essential fats key in fulfilling the needs of the rapidly growing/complex primate brain. Check the latest FAO/WHO report on HUMAN NEEDS FOR FATS AND FATTY ACIDS PUBLISHED BY FAO/WHO see attached document

Great discussion. New insights @ Moududur Rahman Khan and Ricardo

Excellent response Ricardo..

Thank you very much Dr Khan and Dr Uauy for such good explanations.

I am curious that how humans evolved this way that they became so dependent on various plant and animal sources for various nutrients and essential fats while other animals (including primates) are still able to use the magical power of micro organisms to generate nutrients from scratch.

Another question to Dr Uauy I would like to ask is that do you also feel that omega fatty acids are the one which made human race brainy? What is your view on vegetarian populations?

Hi Alka,

Vegetarians can get good amounts of essential PUFAs from their diet. C-18:2 and C-18:3 PUFAs account for over 70% of vegetable cell membrane lipids. Green leaf vegetables provide most of the alpha linolenic acid in the diet. Certain vegetable oils also contain substantial amounts of these fatty acids.

I have already responded , the best response so far by Ricardo ..

Please find some interesting studies...

Being ruminant and having a symbiotic life with their rumen microbiome, cows fulfil their needs for essential amino-acids, glucose and micro-elements.

Thank you very much everyone contributing in my knowledge.

@Dr Khan: What do you suggest is happening in the body of vegetarian people in terms of conversion of ALA and LA to DHA and AA?

A limitation of the human system is that it can’t insert double bond in n-3 and n-6 positions of the FAs. However, it has has enzymes (desaturase) that can insert further double bonds and elongate n-3 and n-6 FAs adding two carbon units at a time once they are in the body from the diet, producing LCPUFAs. This alternating desaturation and chain elongation can produce AA and DHA from LA an ALA, respectively. But there is a catch. The desaturases that catalyse these reactions are not very substrate specific. The n-9, n-6 and n-3 fatty acids, all compete for the same desaturases. Hence, the amounts of essential LCPUFAs the body can make depend on relative amounts of the three starter unsaturated fatty acids. The body itself can make n-9 FAs from palmitic and stearic acids. In essential FA deficiency, 5,8,11-20:3 (n-9) therefore becomes the predominant end product in the body. Some vegetable oils also contain relatively high proportion of n-9 FA compared with the other two. Consuming these oils may also generate inadequate amounts of essential LCPUFAs in body, because the excessive amount of n-9 out competes the other two for the dehydrogenases. Some oil commercials are loud about content of unsaturated FAs but silent about the critical issue of proportion of unsaturated FA families in their products.

Animal and human need 20 essential elements compare to plant need 18 essential elements. As plant like grass may about 70 elements and out of theses contain all-the essential elements and cow as animal has 4th stomach for effective and best digestion of food material like grass and straw.

Cows process food differently from people. I suspect they grind the grass to finer particles than most humans would. They also chew cud, and have multiple chambers in the gut to ferment grass. The end result is that a cow (including its bacterial gut fauna) will extract more from grass than people are capable of doing.

https://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/400/400-010/400-010_pdf.pdf

In addition cows chew cud. Food that was chewed the first time goes to the first chamber. It is then barfed back up to be chewed again. When swallowed the second time it goes to another chamber.

http://cattle-empire.net/blog/115/what-cud-and-why-do-cattle-chew-it

https://en.wikipedia.org/wiki/Cud

I suspect that the transit time is much longer in cows. In humans transit time (from ingestion to elimination) is about 53 hours, or maybe 24 to 72 hours depending on what source you look at. https://www.mayoclinic.org/digestive-system/expert-answers/FAQ-20058340

https://www.livestrong.com/article/525519-the-normal-time-for-food-to-process-through-the-bowels-colon/

This might provide useful information

http://www.vivo.colostate.edu/hbooks/pathphys/digestion/basics/transit.html

I could not find an equivalent time for cows. Maybe Ricardo would be kind enough to answer this? However, like in humans, I suspect that the best answer is not simple.

Quite aporeciative response Timothy.What mechanisms make cows having so high recovery of nutrients from grasses..??

Read more of the cited pages. In brief:

Cows mechanically grind their food into smaller pieces (by the time the food reaches the true stomach) than humans.

Cows ferment their food, and the bacteria provide nutrition.

I suspect that cows retain their food in their digestive tract longer than humans thereby providing more time to break food down and absorb more nutrients from the food relative to what a human could do.

If you need more information, consider the references in the cited pages as a start. However, in biochemical and ecological detail the topic is too broad for RG. Also, Ricardo gave a good answer.

Interesting questions. I have learned a lot already! Thanks!

Thanks Timothy ..an interesting response...

Thank you everyone!! What I am still wondering is how we evolved from animal to human and became so dependent on diet plan? If someone can throw light..

Where animals are still taking the benefits of microbes, we humans are becoming vulnerable day by day trying to find sources for every nutrient.

Everything is dependent on diet. People can get a great deal of nutrition from grass, just not as much as cows. Cats get even less from eating grass than people. A fun question might be to determine if leaf cutter ants get more nutrition from leaves than cows do. The ants cut leaves, and then let them compost in the nest. The ants eat a fungus that grows on the cut leaves.

Evolution is a blend of genetics, ecology, and probability. Genetics holds the code of life. Ecology molds that code. Probability is the random chances that occur wherein a mutation is good or bad, or a tree falls down and prevents a lethal/super mutation to spread in a population. A better answer really should be a couple dozen textbooks.

Humans take advantage of microbes every day. We are full of them, and as we grow up we adapt to a specific blend of microbes. Human nutrition issues can be problems of availability of nutritious food (poorer nations). In some places it is also a problem of poor choices in what to eat. In this case I think of the United States where my daughter prefers eating tortilla chips and ice cream rather than foods with a higher nutritional value.

Animal digestion system is different from human. As cow has forth stomach; so cow may digest two times for grass and straw to complete nutrition from grass and straw..This is the uniqueness of nature .So, food habit of different livings-beings like animal and human may be different.

To the original question "How a cow gets all the nutrients by just eating grass?"... The fermentation process that occurs in the rumen of the animal converts the cellulose, carbohydrates, hemi-cellulose, and starch into microbial protein that is the true food for the animal. This protein has all the critical amino acids as well as Omega 3, 6, 7, and 9 fatty acids. Among the other produced by the process are volatile fatty acids. This process involves the use of over 3,000 species of bacteria, yeast, fungi, and protozoa simultaneously. This is a semi anaerobic process.... it needs a small amount of oxygen the thrive. The process works with a non-homogenous, non-sterile feed stock, under non-sterile conditions to produce a consistent protein.

Cow is a herbivores animal.Food uptake by cow generally grass ,straw etc. contain more carbohydrates than protein. However, carbon contain of straw about 45 % .So, carbon sequestration for microbal population like bacteria,fungi,yeast, protozoa etc.in the stomachs of cow may be dynamic by which protein to amino acid formation comparatively more in stomach of cow may be efficiently more may support protein to nitrogen formation in cowding.In the elementary systems of cow four stomach work simultaneously for efficient nutrients transformation in the ecology of nature.so,cow milk is a nutritional food and cowdung is an ideal orgainc manure; both are beneficial for living beings.

As what Dr Moududur Rahman Khan and Prof Ricardo Uauy pointed out, the key is the microbiomes.

The microbiomes turn grass into all kinds of nutrition, including proteins as they grow, and the cow harvests microbiomes by autophagy (xenophagy). Autophagy captures any microbiome that touch the epithelial cells in GIT of the cow, kill them, degrade them and turn them into amino acids.

Not only the cows can just rely on simple foods, human beings can also just eat simple foods and get super nutrition, if we can build up a large variety species of microbiomes, which can supply a diversity of essential amino acids to our body:

https://www.researchgate.net/post/Why_isnt_nutrition_a_bigger_part_of_conventional_medical_school_education?

A community of microorganisms (such as bacteria, fungi, and viruses) that inhabit a particular environment and especially the collection of microorganisms living in or on the human body:

https://www.merriam-webster.com/dictionary/microbiome

Microbiome are essential for our health. To be too clean will endanger our health:

https://www.researchgate.net/deref/https%3A%2F%2Fwww.dailymail.co.uk%2Fnews%2Farticle-2539704%2FThe-worlds-ineligible-bachelor-Iranian-wash-60-years-smokes-animal-faeces-whip-mean-decomposed-porcupine.html

Keeps food in its bowl

So what I have concluded from this discussion is as we started treating microorganisms with hatred and eliminating 99.9% bacteria from every surface and our body we became dependent on direct sources of nutrients.

I feel glad that microbiome is gaining its importance again but we have come so far that going back might not be possible completely. Crossed fingers! Thank you, everyone! I hope we learn from other organisms to trust nature and not question their capabilities too much.

Dear Dr Alka Rani , Thank you very much for having started this discussion.

Through the discussion, I now get more understanding on why Luigi Cornaro could just rely on small amount of bread, meat, the yolk of an egg and soup, and lived a long and sickness-free life to the great age of 102 in the 15th -16th century (500 year ago):

http://alternativehealthcommunity.com/luigi-cornaro-art-of-living-long/

Dear Prof Naushad Khan

Hi,

Yes, the cellulose in the grass is converted to glucose (microbial community in the stomach of cow), the predominant source of energy. Apart from this, as researchers have said above, the minerals (from the green grass/soil/plants) and the nitrogen (microbial community) are also used up.

A nice, fruitful, sweet and interesting discussion by all researchers on this thread

Microbiology has great role for conversion of carbohydrates,protein ,fat , essential elements etc.of grass, straw etc in ruminants type animal stomach in the ecology of nature.

Microbiology with enzyme transformation of plant body to carbohydrates, protein ,fat, vitamin, hormone etc. in ruminants type stomach animal like cow is more efficient for nutrition

The microbiome of a ruminant utilizes a complex mix of bacteria, yeast, fungi, and protozoa. This ecosystem is continually changing in concentrations of each species based on both the organic matter available and the time in the frementation process. In this process several things are happening. First, the microbes colinize the organic matter and begin to break it down. In that proess a waste stream is generated. Essentially, a microbe breaks a longer carbon chain which becomes the food for another species of microbes. Eventually, the carbon chains are broken down to the lowest energy level. Second, the microbes use the feed as an energy source that enables their reproduction. In this process a portion of the microbes are eventually process out through the rest of th ruminants digestive system. This is the true feed for the animal as it contains a complete protein and lipid mix. The VFA's are absorbed throught rumen wall and become an energy source for the animal. The beauty of this ecosystem is its ability to cellulose, hemi-cellulose, starch and carbohydrates into protein.

Ruminants type animal stomach in cow convert all the essential organic matter convert to major protein nutrition for living beings .So, major grass eating by cow in the ecology of ruminants stomach convert protein to nitrogen nutrition .So,cow dung contain comparatively more nitrogen.

In my humble opinion i think that not completely true, because it depends not only for cow rumen environment but on the type of grass either.