Nutrition in Animals

Food

Introduction

• Plants make their own food through photosynthesis.
• Animals get their food from plants or other animals.
• Importance of Food: Needed for growth, repair, and body functions.
• Animal Nutrition: Includes nutrient requirements, food intake, and food utilization.

Food Components

Food has many components:

1. Carbohydrates
   • Provide energy.
   • Found in foods like rice, wheat, bread, and potatoes.
2. Proteins
   • Help in body building and repair.
   • Found in foods like meat, fish, eggs, beans, and nuts.
3. Fats
   • Provide energy and store it for future use.
   • Found in foods like butter, oil, nuts, and cheese.
4. Vitamins
   • Help in protecting the body from diseases and keep it healthy.
   • Found in fruits, vegetables, dairy products, and grains.
5. Minerals
   • Important for various body functions and to keep bones, teeth, and blood healthy.
   • Found in foods like fruits, vegetables, meat, and dairy products.
6. Dietary Fibers (Roughage)
   • Help in digestion and prevent constipation.
   • Found in foods like whole grains, fruits, and vegetables.

• Complex Substances: Food components like carbohydrates are complex.
• Digestion: Breaking down complex food into simpler substances.

Different Ways of Taking Food

• Modes of Feeding:
  • Bees and hummingbirds: Suck nectar.
  • Human infants: Feed on mother’s milk.
  • Pythons: Swallow prey whole.
  • Aquatic animals: Filter tiny food particles.

Amazing Fact

• Starfish: Feeds on animals with hard shells by popping out its stomach to eat the soft inside.

Digestion in Humans

• Process: Food taken in through the mouth, digested, and unused parts defecated.
• Alimentary Canal: Continuous canal from mouth to anus, includes:
  1. Buccal cavity
  2. Foodpipe (oesophagus)
  3. Stomach
  4. Small intestine
  5. Large intestine ending in rectum
  6. Anus
• Digestive Juices: Secreted by stomach, small intestine, salivary glands, liver, and pancreas to break down food.

a. The Mouth and Buccal Cavity

• Ingestion: Taking food into the body through the mouth.
• Teeth:
  • Different types with different functions (biting, cutting, piercing, tearing, chewing, grinding).

More to Know

• Milk Teeth and Permanent Teeth:
  • Milk teeth: First set, falls out at age 6-8.
  • Permanent teeth: Replace milk teeth, can last for life.

Sweets and Tooth Decay

• Bacteria: Present in the mouth, harmful bacteria grow if the mouth isn’t cleaned.
• Tooth Decay: Caused by bacteria breaking down sugars and releasing acids.
• Prevention:
  • Brush teeth twice a day.
  • Rinse mouth after meals.
  • Avoid putting dirty fingers or objects in the mouth.

Salivary Glands and Saliva

• Salivary Glands: Secrete saliva in our mouth.
• Saliva’s Action: Breaks down starch into sugars.

The Tongue

• Functions:
  • Talking
  • Mixing saliva with food
  • Helping in swallowing
  • Tasting food with taste buds

b. The Foodpipe/Oesophagus

• Function: Carries swallowed food from the mouth to the stomach.
• Movement: Walls of the foodpipe push food downwards through the alimentary canal.
• Vomiting: Occurs if the stomach rejects food.

Choking and Windpipe

• Eating in a Hurry: Can cause coughing or hiccups if food enters the windpipe.
• Windpipe and Foodpipe: Share a common passage in the throat.
• Swallowing Mechanism: A valve prevents food from entering the windpipe during swallowing.

c. The Stomach

• Structure: Thick-walled, J-shaped bag; widest part of the alimentary canal.
• Function: Receives food from the foodpipe and opens into the small intestine.
• Inner Lining: Secretes mucous, hydrochloric acid, and digestive juices.
  • Mucous: Protects stomach lining.
  • Hydrochloric Acid: Kills bacteria, creates an acidic environment.
  • Digestive Juices: Break down proteins into simpler substances.

Interesting Fact

• Discovery of Stomach’s Working:
  • In 1822, Alexis St. Martin was shot, causing a hole in his stomach.
  • Doctor William Beaumont observed the stomach’s function through this hole.
  • Found that the stomach churns food and secretes fluid for digestion.
  • Noted that the stomach opens into the intestine only after food is digested.

d. The Small Intestine

• Length: About 7.5 meters, highly coiled.
• Secretions:
  • Liver: Secretes bile juice stored in the gall bladder; helps digest fats.
  • Pancreas: Secretes pancreatic juice; acts on carbohydrates, fats, and proteins.
  • Intestinal Wall: Secretes juices to complete digestion.

Digestion Process

• Carbohydrates: Broken into simple sugars (e.g., glucose).
• Fats: Broken into fatty acids and glycerol.
• Proteins: Broken into amino acids.

Absorption in the Small Intestine

• Process: Digested food passes into blood vessels in the intestinal walls (absorption).
• Villi: Finger-like outgrowths increasing the surface area for absorption.
  • Each villus has small blood vessels.
  • Villi absorb digested food, transporting it via blood to organs for assimilation.
• Assimilation: Body uses absorbed substances to build complex materials (e.g., proteins).
  • Energy Release: Glucose breaks down with oxygen into carbon dioxide, water, and energy.
• Undigested Food: Passes into the large intestine.

e. Large Intestine

Structure and Function

• Size: Wider, shorter (about 1.5 meters).
• Function: Absorbs water and salts from undigested food.
• Waste: Forms semi-solid faeces, stored in the rectum.
• Egestion: Removal of faecal matter through the anus.

Diarrhoea

Causes and Effects

• Causes: Infection, food poisoning, indigestion.
• Common in India: Especially among children.
• Severe Effects: Can be fatal due to excessive loss of water and salts.

Treatment

• Immediate Care: Give plenty of boiled and cooled water with salt and sugar (ORS) before consulting a doctor.

Digestion in Grass-Eating Animals

Ruminants and Rumination

• Grass-eating animals like cows and buffaloes chew a lot, even when not eating.
• They swallow grass quickly and store it in a stomach part called the rumen.
• In the rumen, food gets partially digested and is called cud.
• The cud later comes back to the mouth in small lumps for chewing.
• This process is called rumination.
• Such animals are called ruminants.

Digesting Cellulose

• Grass has cellulose, a carbohydrate.
• Bacteria in the rumen help digest cellulose in ruminants like cattle and deer.
• Humans and many other animals cannot digest cellulose.

Caecum in Non-Ruminants

• Animals like horses and rabbits have a large sac-like structure called the caecum.
• The caecum is located between the oesophagus and the small intestine.
• Certain bacteria in the caecum digest cellulose here, which humans do not have.

Feeding and Digestion in Amoeba

Structure of Amoeba

• Amoeba is a tiny, single-celled organism found in pond water.
• It has a cell membrane, a dense nucleus, and many small vacuoles in its cytoplasm.
• Amoeba constantly changes shape and position.

Movement and Feeding

• Amoeba uses finger-like projections called pseudopodia (false feet) to move and capture food.
• When it senses food, it surrounds and engulfs it with pseudopodia.
• The food gets trapped in a food vacuole.

Digestive Process

• Digestive juices in the vacuole break down the food into simpler substances.
• Digested food is absorbed and used for growth, maintenance, and multiplication.
• The undigested residue is expelled outside by the vacuole.

Common Digestion Process

• The basic process of digesting food and releasing energy is the same in all animals.
• Absorbed food is transported to various parts of the body, which will be discussed in a later chapter.

Chapter Summary:

• Animal nutrition includes nutrient requirements, how food is taken in, and how it is used in the body.
• The human digestive system has the alimentary canal and secretory glands.
• The alimentary canal consists of:
  1. Buccal cavity
  2. Oesophagus
  3. Stomach
  4. Small intestine
  5. Large intestine ending in rectum
  6. Anus
• The main digestive glands that secrete digestive juices are:
  1. Salivary glands
  2. Liver
  3. Pancreas
• The stomach wall and the wall of the small intestine also secrete digestive juices.
• Different organisms have different modes of feeding.
• Nutrition is a complex process involving:
  1. Ingestion
  2. Digestion
  3. Absorption
  4. Assimilation
  5. Egestion

Keywords

No.	Keyword	No.	Keyword
1	Absorption	16	Ingestion
2	Amino acid	17	Liver
3	Amoeba	18	Milk teeth
4	Assimilation	19	Molar
5	Bile	20	Permanent teeth
6	Buccal cavity	21	Oesophagus
7	Canine	22	Pancreas
8	Cellulose	23	Premolar
9	Digestion	24	Pseudopodia
10	Egestion	25	Rumen
11	Fatty acid	26	Ruminant
12	Food vacuole	27	Rumination
13	Gall bladder	28	Salivary glands
14	Glycerol	29	Villi
15	Incisor	30	Saliva