O Level Revision : Combined Science - Animal Nutrition

This is a system of organs that are involved in the breakdown of large insoluble food molecules. The system starts in the mouth and ends with the anal opening.

Human alimentary canal

Parts of the alimentary canal

• Oesophagus (gullet) Stomach
• Pancreas
• Small intestine (ileum) Large intestine (colon)
• Rectum
• Anus

There are two major systems to be compared; ruminant and non-ruminant.

Differences between ruminant and non-ruminant alimentary systems

Digestive system of (a) a cow – ruminant             (b)  a rabbit – non ruminant

Functions of the different parts of the digestive system

Functions of alimentary systems organs

The small intestines consist of two parts namely duodenem and ileum.

Digestion

Definition:   It is the breakdown of large insoluble food molecules into smaller soluble forms.

There are two forms of digestion, namely:

1. a) Physical/mechanical digestion –involves breaking down food using force through grinding or churning.
2. b) Chemical digestion – involves chemical substances like the gastric juices and

– helps to digest food into smaller soluble molecules.

Importance of digestion

1. Decreasing the size of food molecules.
2. Increasing the solubility of food molecules for absorption and utilisation by the animal.

• Typical enzyme action can be demonstrated using enzyme amylase.
• When amylase is added to a starch solution it converts the starch to a simple sugar called maltose.

The action of amylase on starch

The enzyme amylase is found in the mouth. It is referred to as salivary amylase because it is found in saliva.

After leaving the mixture in a beaker maintained at about 37OC for a while, then a test for starch is negative in B while a test for sugar maltose is positive. This is because amylase acted upon starch and converted it to a simple sugar (maltose) hence a negative starch test result in B.

Absorption and assimilation

Soluble food molecules are absorbed into the blood system through diffusion and active uptake in the small intestines. This is facilitated by villi in small intestines which increase the surface area for absorption.

Definition:  Assimilation is a process in which the absorbed nutrients are used in the body tissues. a)  Carbohydrates are used for energy.

1. b) Amino acids are used for growth and repair of tissues.
2. c) Fatty acids and glycerol are used for energy storage and warmth.
3. d) Surplus glucose and fatty acids are converted to storage forms. Glucose is converted into glycogen and fatty acids and glycerol are converted into This fat may be converted to adipose tissue, the fat layer below the skin.
4. e) The liver controls the conversion of excess nutrients into storage products.

Growth and development

There is need for good balanced rations at different stages of growth in farm animals. This insures proper growth and development of the animals.

From the sigmoid graph, one is expected to be able to describe the growth of animals and determine times when it is best to slaughter the animals.

✓   The graph (Fig 2.2) shows three stages of growth.

✓   Animals should be slaughtered just after the stage with a high growth rate.

✓   Animals which continue to be kept alive after this stage can no longer efficiently convert food into body mass.

Animals parasites and diseases

Definition: A parasite is an organism that live on or in another organisms to the detriment of the host organism.

• Organisms such as ticks, flukes and tsetse flies are parasites.
• Parasites that live on the host are external parasites and those that live in the host are internal parasites.
• Some external parasites carry disease-causing micro-organisms. Such parasites are
• called vectors and examples are mosquitos, tsetse flies and ticks.
• Parasites that cause disease are referred to as pathogenic.

 Some diseases caused by parasites

Effects of Parasites

Parasites and diseases basically reduce productivity through the following:

• reduced  yield of produce (meat, milk, offspring, eggs),
• reduced quality of meat, milk and off springs,
• death in animals.

Control of parasites and diseases

The methods used in the control of parasites and diseases include:

1. Dipping - for ticks.
2. Dosing - for flukes.
3. Quarantine - done for notifiable diseases such as foot and mouth and anthrax.
4. Vaccination - done for notifiable diseases.
5. Destruction - two ways are used, these are burning or burying infected animals.