LEARNING OBJECTIVES: At the end of the lesson, students should be able to

1. Identification 
2. Digestion
3. Circulatory system
4. Reproduction system 

CONTENT: ANATOMY AND PHYSIOLOGY OF FARM ANIMALS 

Anatomy and physiology of farm animals

CONTENT:

• Digestive system
• Circulatory system
• Reproduction system

Digestive system

1. Digestive system and digestion
2. Digestion in ruminant (polygastric) animals
3. Digestion in non-ruminant (monogastric) animals
4. Digestion in poultry birds
5. Differences between monogastric and polygastric animals.

Digestive system and digestion:

The digestive system of farm animals includes all the organs and tissues associated with the breaking down or digestion of food in the body. It includes the teeth or beak, tongue, the alimentary canal or digestive tract and all the associated gland secreting enzymes and other body fluids.

Digestion is the breakdown of foods substances in the digestive tract into absorbable forms. This process starts from the mouth through mastication which increases the surface area and allows microbes to have quicker access to act the food substances.

Farm animals are grouped into two main classes based on the nature of the alimentary canal or digestive tract. There are polygastric (ruminant) animals and monogastric (non – ruminant) animals.

Digestion in ruminant animals:

These are farm animals which possess complex stomach made up of four compartments or chambers. These are rumen (paunch) which is the first, reticulum or forestomach (honeycomb), omasum (the fardel, manyplies or psalterium) and abomasum (true stomach). These animals can ruminate or chew the cud. Example of farm animals having this stomach compartment includes cattle, sheep, goat etc.

Cattle for example when feeding gathers some quantity of grasses with its tongues and grip it firmly between the upper jaw and the teeth of the lower jaw; it jerks its head and swallows the grasses. The grasses pass through the oesophagus and enter the rumen, where digestion of cellulose by bacteria takes place.

When the cattle has filled its rumen,  it lies down quietly and by the antiperistaltic movement of the stomach, the undigested grass or cud passes from the rumen to the reticulum from where it goes back to the oesophagus and back to the mouth to be masticated (this process is referred to as regurgitation).  It then chews the food properly into a semi-liquid cud (bolus) with the premolars and molars which re-swallowed.

The cud moves into the omasum and passes into the last chamber, abomasum where gastric juice containing digestive enzymes are secreted into the semi-digested food to form the chyme. The chyme goes into the small intestine through the duodenum where further digestion and absorption of nutrients takes place. The undigested material then passes out through the anus as dung.

 Digestion in non-ruminant animals:

These animals possess only one stomach structure and they do not ruminate (that is they do not chew the cud). The animals cannot digest cellulose and fibres properly. Examples include pigs, poultry etc. Pig has a simple stomach. It feeds mainly on basal feeds like maize, cassava and other meshed food. Digestion of foods takes place in four areas of the tract.

1. Mouth: In the mouth, the food is changed and mixed with saliva which contains an enzyme Ptyalin. Ptyalin converts starch to maltose. The food (bolus) is then swallowed and moved by a peristaltic movement to the stomach.
2. Stomach: here, two enzymes, pepsin and rennin are present. Renin act on milk and pepsin convert protein to peptones. The thick liquid formed (chyme) now passes to the duodenum.
3. Small intestine
4. Duodenum: Here, the pancreas secretes pancreatic juice which contains three digestive enzymes i. e.

• Amylase – Converts starch to maltose
• Lipase – Converts fats and oil to fatty acid and glycerol
• Trypsinogen – Converts protein and peptones to polypeptides

The digestion of fats and oil is aided by bile. Bile helps in the emulsification of fats. At the duodenum, the food now in liquid form called chyle passes to the ileum of the small intestine. In the Ileum, secretion of enzymes which furthers the process of digestion takes place. These enzymes are

1. Lipase: convert fats and oil to fatty acid and glycerol
2. Erepsin: Converts polypeptides to amino acid
3. Maltase: Converts maltose to glucose
4. Lactase: converts lactose to glucose and galactose
5. Sucrase: converts sucrose to glucose and fructose

The end product in the digestion of protein is an amino acid, starch is glucose and fats and oil is fatty acid and glycerol.

 Digestion in poultry birds:

The domestic fowl is a monogastric animal that possesses a simple stomach. The fowl has no teeth but the food is picked up by the beak. The food then passes on to the crop through the oesophagus. The food is stored temporarily in the crop, there moistened and fermented by some bacteria. The food now passes on to the proventriculus (glandular stomach) where digestive juice such as pepsin and amylase is secreted on the food.

From the proventriculus, the food moves to the gizzard where grinding of the food takes place. From the gizzard, the food moves to the small intestine where further digestion and absorption takes place. The undigested food materials are removed from the digestive tract as faeces.

 Differences between monogastric and polygastric animals

 Circulatory system

The circulatory system consists of all the tissues and organs that are involved in the transportation of materials through the blood round the body of farm animals. Farm animals possess a closed circulatory system. This means that oxygenated and deoxygenated blood does not mix. They also display a pattern of double circulation (this mean that for one complete circulation to occur, the blood must pass through the heart twice; first to the lungs for oxygenation and then on return to the other parts of the body) or single circulation as in the case of fish. The circulatory system has three (3) main divisions. These are:

1. The Blood
2. The Blood vessels, and
3. The Heart

The blood:

Mammalian blood is made up of plasma and blood cells, which are;

1. Plasma (the liquid part of the blood): It contains water, blood proteins (e.g. fibrinogen), dissolved mineral salts, waste products, and digested food.
2. The Blood Cells(corpuscles)
3. Red blood cells (Erythrocytes): biconcave, circular in shape and no nucleus when matured, contain an iron pigment called haemoglobin that helps to transport oxygen, produced in bone marrow,
4. White blood cells (Leucocytes): irregular in shape, few than red blood cells, have a nucleus, produced in lymphatic tissues. They defend the body against foreign bodies.
5. Blood platelets (Thrombocytes): irregular or star-shaped, tiny, non-nucleated, produced for blood clotting.

Functions of the blood

1. Maintain body temperature through uniform distribution.
2. Carries oxygen through the red blood cells.
3. Transports hormones from the ductless gland
4. Transport metabolic waste to where they are removed.
5. Defend body against germs via leucocytes
6. Platelets help in blood clotting
7. Transports digested food to the cell.
8. Maintain water level and turgidity of the body

The blood vessels:

These are a network of spaces in the body through which material is moved from one part of the body to the other with the aid of blood. There are three major blood vessel, they are:

1. Artery: carries blood away from the heart to other parts of the body. It further divides into arterioles.
2. Vein: this vessel carries blood back to the heart from other parts of the body. It further divides to form veinous.
3. Capillaries: tiny blood vessel around tissues and organs where arteries and veins meet.

The heart:

This is a muscular organ responsible for pumping blood around the body. Each pump action of the heart is known as a heartbeat. The heart is located in the thoracic cavity of the body, protected by the pericardium. It consists of four chambers: the upper: auricle (right and left), the lower: ventricles (right and left). A central wall divides the right and left part of the heart called septum. The auricles and ventricles are divided on the right by a tricuspid valve and on the left by a mitral/bicuspids valves.