How does digestion in a cow work? Sara Syswerda and Brook Wilke

Cows compared to us: What makes ruminants different? Humans are mongastrics, as are pigs, dogs, and cats. Ruminating mammals include cattle, goats, sheep, giraffes, bison, yaks, water buffalo, deer, camels, alpacas, llamas, wildebeest, antelope, pronghorn, and nilgai.

Cows compared to us: What makes ruminants different? Ruminants take more time to move stuff through the stomach, and the food goes through multiple chambers where microbes can work on the materials and break down the cellulose and hemi-cellulose. Cows don’t actually digest the plants with acid any different than we do, but they have microbes work on the plants first, and often times just eat the microbes.

Food comes in through the mouth to the esophagus… Food can come in the esophagus, and can also be regurgitated (“chewing their cud”)

Food enters the rumen/reticulum, and is mixed with saliva Food is separated into liquid and solid, and the mat of solid is what is regurgitated as cud. Food can come in the esophagus, and can also be regurgitated (“chewing their cud”). The rumen and reticulum, while separate chambers, are open and the mixture moves in between these two chambers. Liquid tends to move through pretty fast, but solids move through pretty slowly. This chamber is where most of the microbes live and release enzymes to help digest the food. The pH in here is pretty neutral due to buffers in the saliva, and that is very important to maintain the right mix of microbes.

Omasum the omasum, where water and many of the inorganic mineral elements are absorbed into the blood stream

Abomasum: The True Stomach After this the digesta is moved to the true stomach, the abomasum. The abomasum is the direct equivalent of the monogastric stomach (for example that of the human or pig), and digesta is digested here in much the same way. . In contrast to the stomach of non-ruminants, the abomasum secretes lysozyme, an enzyme that efficiently breaks down bacterial cell walls. This is the only portion of the stomach that is markedly acidic.

Digesta is finally moved into the small intestine, where the digestion and absorption of nutrients occurs. Microbes produced in the reticulo-rumen are also digested in the small intestine.

Gas Facts Fermentation in the rumen generates enormous, even frightening, quantities of gas. We're talking about 30-50 liters per hour in adult cattle. Eructation or belching is how ruminants continually get rid of fermentation gases. The rumen is anaerobic, lacking oxygen. Many other gases are present, including methane and hydrogen.

Let’s think about where the matter and energy is going in this system: What are the inputs and outputs? What sort of activities or transformations are going on here? Who are the key players we need to be thinking about here?

process tool Digestion in animals Scale: (energy input) (energy output) (matter output) (matter input) Scale:

process tool Photosynthesis Scale: (energy input) (energy output) (matter output) (matter input) Scale:

process tool Scale: (energy input) (energy output) (matter output) (matter input) Scale:

Question How would you simulate digestion in a cow so that students could see digestion in their classroom? How would digestion go differently if cows were eating other stuff instead of grass? Corn? Potato flakes? Donuts?

Simple digesters The diameter of the balloon will indicate to what extent digestion progressed. Fermentation Gases are collected at the top Place warm water, yeast, and material to be digested in the bottom