Nutrition in Animals
All living organisms (both plants and animals) need certain nutrients to be alive and grow. Food is the source of these nutrients. Plants can prepare their own food through photosynthesis, while animals consume foods from plants. In the below article let us go through various mechanisms of nutrition in animals.
Definition of Nutrition
Each and every animal requires food for energy to perform various activities like running, walking, jumping, reading etc. This energy is obtained from the food they eat. In order to obtain energy, the food that they eat need to be digested and then assimilated. Hence nutri
Requirement of nutrients, mode of intake of food and its utilization in body are collectively known as nutrition. Some animals eat plants directly while some animals eat plant eating animals. Thus, animals get their food from plants either directly or indirectly.
Broadly all the animals can be divided into three groups on the basis of their food habits. These are:
- Herbivores: Animals eating only plants are called herbivores. Examples are Goat, Cow, and Deer etc.
- Carnivores: Animals eating only other animals as food are called carnivores. Examples are Lion, Tiger, and Lizard etc.
- Omnivores: Animals which eat both plants and animals are called omnivores. Examples are Man, Dog and Crow etc.
Steps involved in the intake of Nutrition in Animals
Also known as holozoic nutrition, it is a process by which animals take in their food. It involves five basic steps:
- Ingestion: The process of taking food into the body is called ingestion.
- Digestion: Large, insoluble molecules present in the food are broken down into small, water-soluble molecules. This is called digestion.
- Absorption: The process in which the digested food passes through the intestinal wall into the bloodstream is called absorption.
- Assimilation: In this process, the absorbed food is taken in by the body cells and further used to generate energy, repair and growth. Oxygen and nutrients are supplied to our cells by this process.
- Egestion: The process in which the undigested food is removed from the body is called egestion. The faecal matter is removed through the anus from time-to-time.
Humans also exhibit holozoic nutrition.
Digestive system in animals
Image Credits: Ek Shiksha
Various organs of the human digestive system in a sequence are
Mouth (Buccal cavity): The mouth or buccal cavity contains teeth, tongue and salivary glands. Teeth are used for cutting, grinding and tearing the food before you swallow it. There are two types of teeth- milk teeth and permanent teeth. The tongue is a muscular organ which helps in mixing saliva in the food and pushing the food down the food-pipe or oesophagus. Taste receptors are present on tongue and give us the sense of taste.Image Credits: Ek Shiksha
Oesophagus (Food pipe): It is a 30 cm long tube-like structure connecting the mouth and the stomach. It contracts and relaxes in a rhythmic fashion to facilitate the forward movement of food. No digestion takes place here.
Stomach: It is a muscular J- shaped thick walled bag which receives food at one end from food pipe and opens into the small intestine on the other end.Gastric juice is secreted from the wall of the stomach and mixed with food. Gastric juice contains some enzymes and hydrochloric acid which helps in breaking down protein from food. The hydrochloric acid kills the harmful bacteria (if any) present in the food and helps the gastric enzymes to work.
Small Intestine: It is about 20 feet long highly coiled tube consisting of three parts: duodenum, jejunum and Ileum. In the duodenum, the liver secretes bile juice and pancreas pour in the pancreatic juice. The bile juice contains the bile which carries out emulsification of fat. The pancreatic juice contains several enzymes which catalyse break down of starch into simple sugars and proteins into amino acids. From duodenum, the food goes to the lower part of the intestine. There are numerous finger-like projections on the wall of the small intestine. These projections are called villi which have fine blood capillaries to absorb the food. Post absorption; food mixes in the bloodstream and is carried by the blood to all the cells of the body. The cells utilize this food to release energy.
Large intestine: In large intestine; excess of water from the materials is absorbed. The semi-solid residue is stored in the last part of the large intestine called rectum and finally throw out of the body through the anus from time to time.
The digestive mechanism in grass-eating animals
Grass eating animals like cows, buffaloes are called ruminants because they have a separate part of the stomach called rumen.They quickly swallow the grass and store in rumen where it is partially digested forming cud. Rumination is the process by which cud returns to the mouth in small lumps and then the animal chews it. Grass contains cellulose which is digested by special bacteria present in a sac-like structure located between the small intestine and large intestine.
Things to remember
- Carbohydrates, proteins, fats and minerals are significant components of food. These components are known as nutrients.
- Since animals and most other organisms take in ready-made food prepared by the plants, they are called heterotrophs.
- The mode of feeding varies from organisms to organisms.
- Digestion of carbohydrate (like starch) begins in the buccal cavity and the digestion of protein starts in the stomach.
Nutrition in animals is all about studying the sciences behind animal nutrition. It is not limited to, fundamental aspects of animal nutrition such as nutritional requirements, metabolic studies, body composition, energetics, immunology, neuroscience, microbiology, genetics and molecular and cell biology related to nutrition, and more applied aspects of animal nutrition, such as raw material evaluation, feed additives, nutritive value of novel ingredients and feed safety.
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