Digestive differences…and why it matters


All hail to the the King…er…Queen of farm animals. Pictured here is the young virgin queen Elizabeth, with a pedigree traceable all the way back to the Isle of Jersey hundreds of years ago (and I don’t even know the first names of my great grandparents).

Cattle, goats, sheep, and animals like deer, elk, and buffalo are ruminants. The key physiological feature of these animals, and the reason why they are the dominant terrestrial herbivores (or plant predators, my preferred term), is their sophisticated and marvelous digestive system featuring a four-chambered stomach, the first chamber of which is called the rumen, which allows a ruminant to marshal legions of microorganisms that employ unique enzymes that efficiently break down cellulose into digestible carbohydrates. Low-nutrient density foods like grass not only sustain such animals, but enable them to grow rapidly to often-enormous size. I like to think that our gift as humans is our well-developed brain, and it is easy to become brain-proud, but in my relations with cattle, I have come to appreciate just how magnificent these animals are because of their well-developed stomachs. I like to think of them as stomach-proud. Low nutrient density plants, like cool-season grasses, I would starve on no matter how much I ate of them, while my cow has grown to 5x my body weight in just 18 months eating mostly cool-seasons grasses and legumes. The rumen is more efficient that any man-made cellulose digester, by the way, and a cow reproduces herself every year, while a cellulose digester has yet to produce a baby cellulose digester. To me this is highly impressive.

Ruminants contrast with the other farm food animals: poultry and pigs. Both poultry and pigs require feed of nutrient density approaching that of our own needs. In fact, a man could live on pig or chicken feed. What these animals do on a farm is convert low-value food into higher-value food. On today’s farm, they convert grain and soybeans into eggs and meat. There is nothing wrong with this, however, it is important to realize the differential in value is relatively small, as humans can live on grain and soybeans, and some cultures historically have. In the process of conversion, many calories are wasted, too. The most efficient converter, the Cornish-Rock broiler chicken, weighs at slaughter roughly half to a third of how much feed it consumed over its 8-11 week life. The remaining calories are lost as heat and excrement, and really lost to the atmosphere if the excrement isn’t recaptured as a fertilizer. And most people throw away their chicken bones (a small crime in my reckoning). Pork bones make only an inferior broth.

Ruminants produce much more value because they are capable of converting nearly worthless food (grass and forage legumes and forbs) into extremely nutritious milk and red meat. They also produce heavy bones, which are far more useful than pork or poultry bones, leather, wool and hides (pig skin is somewhat useful, but chicken feathers are next to useless). Quite simply, the ruminant is one of the fundamental sources of wealth creation, along with mines and field crops. It is why the flock and especially the herd have always been symbols of wealth.

One of the problems with ruminants is that they require rather extensive holdings of land to be fed, and so smallholders like me (my farm is 11 acres) are told to keep chickens and pigs and sometimes rabbits. Using agronomic averages for my area, a dairy cow needs around 3.5 acres of pasture and may need grain and hay supplementation. Historically for this reason places with high population densities, like Southeast Asia, have not relied on ruminants. The limited acreage available was used for growing high calorie per acre rice (only modern corn surpasses rice in calories per acre) and high nutrient per acre vegetables. Milk was rare, and the little bit of meat came from poultry or pigs that can be fed surplus or spoiled people food (rice, vegetables, and scraps) on hardly any acreage. Pig and poultry confinements are measured in square feet, not acres. One can keep a broiler in just one square foot, and a pig in as little as 10 square feet, but I don’t recommend this. An acre is 43,560 square feet, so it takes 152,460 square feet per cow where I live using conventional methods. That’s quite a difference. Even when one confines a cow to a barn and feeds her hay or silage and grain, like in the modern dairy barn, she needs about 100 square feet to me happy–10x more than a pig needs.

This has changed in the last century, though. A technological innovation and an insight into plant biology have allowed for a much greater number of ruminants to be kept on the same acreage. Now ruminants may be kept so that they rival or exceed non-ruminants for total production per acre. And since ruminants should eat mostly perennial forages (as opposed to annual plants like corn, wheat, soybeans, etc.) tractor and tillage based agriculture, which annuals require, is reduced. Truly, today’s “alternative” farmers stand on the precipice of a revolution that holds the key to solving the conundrum of feeding an ever growing population without a proportional increase in combustion of fossil fuel, as is required by any sort of tractor-tillage-grain based agriculture. Even no-till organic methods rely on tractors and fossil fuel to a much larger degree than animal-powered ruminant agriculture. Until the day comes (and I doubt it will) that perennial wheatgrass approaches the productivity of ordinary annual wheat in per acre terms, which is what the good folks at the Land Institute have been working on for decades, the most environmentally benign agriculture is ruminant-based.

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