Tag: what do animals eat?

The process in the alimentary canal by which food is broken up physically, as by the action of the teeth, and chemically, as by the action of enzymes, and converted into a substance suitable for absorption and assimilation into the body.

• Continuous feeders: That must "eat" constantly because the food is taken in and then pushed out soon afterwards are called continuous feeders. Most of these animals either are permanently attached to something (such as clams or mussels) or are very slow moving.
  
• Discontinuous feeders: Consume larger meals and store the ingested food for later digestion. These animals generally are more active and can avoid predators. Hence, the animals that feed discontinuously must have digestive tracts that permit storage and are able to avoid predators by limiting their feeding time.

The ruminants bring back swallowed grass into their mouth and chew it for sometime. Grass has cellulose. It is the carbohydrate which can only be digested by ruminants because they have rumen. When they eat grass, it is sent to the rumen where enzymes acts on it and softens it. Softened cellulose is called cud. It is sent back to the mouth where ruminants chew it for sometime.

Methanogens are a group of archaebacteria that occur in marshy areas where they convert formic acid and carbon dioxide into methane. Some of the methanogen archaebacteria live as symbionts (Eg. Methanobacterium) inside the rumen or first chamber in the stomach of herbivorous animals that chew their cud (ruminants). These archaebacteria are helpful to the ruminants in the fermentation of cellulose. 

In ruminants, the stomach is differentiated into separate chambers - rumen (for churning, digestion of cellulose and hemicellulose and bacterial fermentation), reticulum (traps and stores temporarily large feed particles), omasum (absorbs water) and abomasum (similar to human stomach, digests proteins). Abomasum is the true stomach. Omasum is absent in camels. In camels rumen and reticulum have diverticula or water pockets for temporary storage of food.

Ruminants (cattle, sheep, deer, giraffes) are hooved animals with a stomach divided into four chambers- rumen, reticulum, omasum, and abomasum. Symbiotic bacteria and protists living in the first two chambers digest cellulose, splitting some of it into sugars, which are then used by the host and the bacteria themselves. The bacteria produce fatty acids during their metabolism, some of which are absorbed by the animal and serve as an important energy source. Food that is not sufficiently chewed clumps together, forming a cud. The cud is regurgitated into the animals mouth, where it is mixed with saliva and chewed again. When the cud is reswallowed, the partly digested food is further broken down by the cows own enzymes.

Cud is a portion of food that returns from a ruminant's stomach to the mouth to be chewed for the second time. Cows spend nearly eight hours out of every day chewing their cud. Hence, option A is correct.

The ruminant stomach is composed of 4 separate compartments. Food passes first into the 'rumen', then 'reticulum', 'omasum' and finally into the 'abomasum'. The first three compartments helps in digestion of complex carbohydrates with the aid of microorganisms, which produce volatile fatty acids. The abomasum functions similarly to the carnivore stomach as it is glandular and digests food chemically, rather than mechanically or by fermentation like the other 3 chambers of the ruminant stomach. Hence, option A is correct.