Friday Science Blogging

A ruminant is any hooved animal that digests its food in two steps, first by eating the raw material and regurgitating a semi-digested form known as cud, then eating the cud, a process called ruminating. Ruminants include cattle, goats, sheep, llamas, giraffes, bison, buffalo, deer, wildebeest, and antelope. The suborder Ruminantia includes all those except the camels and llamas, which are Tylopoda. Ruminants also share another anatomical feature in that they all have an even number of toes.

Explanation

Ruminants have a fore-stomach with four chambers. These are the rumen, reticulum, omasum, and abomasum. In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud (or bolus). The cud is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fibre, especially cellulose and hemi-cellulose, is primarily broken down into the three volatile fatty acids, acetic acid, propionic acid and butyric acid in these chambers by bacteria and protozoa.

Even though the rumen and reticulum have different names they represent the same functional space as digesta can move back and forth between them. Together these chambers are called the rumen-reticulum. The degraded fibre, which is now in the lower liquid part of the rumen-reticulum, then passes into the next chamber, the omasum, where water and many of the inorganic mineral elements are absorbed into the blood stream. After this the digesta is moved to the last chamber, the abomasum. The abomasum is the direct equivalent of the monogastric stomach (for example that of the human or pig), and food here is digested in much the same way. Digesta is finally moved into the small intestine, where the digestion and absorption of nutrients occurs. Bacteria created in the reticulo-rumen are also digested in the small intestine.
Almost all the glucose produced by the breaking down of cellulose, hemicellulose and lignin is used by bacteria in the rumen, and as such ruminants usually absorb little glucose from the small intestine. Rather, ruminants' requirement for glucose (for brain function and lactation if appropriate) is made by the liver from propionate, one of the volatile fatty acids made in the rumen.

The idea for this Friday's contribution to the understanding of science is from Katie, a lovely young lady. We were talking about cows. She said cows aren't supposed to eat grain; they should eat grass. It seems that advice has been heard before, perhaps it was a discussion of organic farming or safe beef. Not sure. In any case, I hope to see her again as there are now more questions re safe food sources.

Wiki