Nutrition and digestion are the main characteristics of living entities and are inter-related. Nutrition is obtained from food after the process of digestion. Animal nutrition covers topics such as the requirement of nutrients, mode of intake, utilization of food in the body. Some nutrients are complex in nature and cannot be utilized directly. They require to be broken down into simpler substances, this process is called digestion.
Food is consumed differently by different entities. Hummingbirds and bees suck nectar of plants, snakes swallow their prey, fish feed on floating food particles etc. Digestion is carried out by the digestive system consisting of distinct organs.
Digestion in humans is carried out by an organized and distinct digestive system. Food is ingested through the mouth and enters into the food pipe or oesophagus through the pharynx and finally to the stomach. On reaching the stomach, complex food is broken down into simpler substances by secreting digestive juices with the absorption of nutrients. Undigested food is further directed to small and large intestine which carries out further absorption. Unwanted waste is directed to the rectum for excretion.
Grass eating animals are known as ruminants. Animals like cows, goats and buffaloes eat grass. These animals swallow grass quickly and store in a sac-like structure called rumen. Rumen forms the first stomach and is four-chambered. Here, food is partially digested and is called the cud. Plants contain cellulose in large quantities. Cellulose is a complex structure which is broken down into simpler particles in the rumen. The process where cud returns to the mouth in small lumps for ruminants to chew is called rumination.
Rumination is aided by bacteria present in the rumen which breaks down cellulose in plants. The digested food is then passed to the reticulum. Some animals including humans cannot digest cellulose for its complex structure.
Some animals have a large sac-like structure called caecum which is present between the food pipe or the oesophagus and the small intestine. For example Rabbit, Horses. Cellulose in food is digested by the action of bacteria which humans do not possess.
Some examples of grass-eating animals:
- American Bison
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