ANATOMY AND PHYSIOLOGY OF FARM ANIMALS

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 food 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 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 a complex stomach made up of four compartments or chambers. These are rumen (paunch), which is the first, reticulum or fore stomach (honeycomb), omasum(the fardel, manyplies or psalterium) and abomasum (true stomach).

These animals can ruminate or chew the cud. Examples of farm animals having this stomach compartment include cattle, sheep, goat, etc.

Cattle, for example, when feeding, gather some quantity of grass with their tongues and grip it firmly between the upper jaw and the teeth of the lower jaw; it jerks its head and swallows the grass. 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 anti–peristaltic 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, the abomasum, where gastric juice containing digestive enzymes is 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 take place. The undigested material then passes out through the anus as dung.

EVALUATION

1. What are ruminant animals? Give five examples.
2. Describe briefly the digestion in cattle.

 

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 the enzyme Ptyalin. Ptyalin converts starch to maltose. The food (bolus) is then swallowed and moved by peristaltic movement to the stomach.
2. Stomach: Here, two enzymes, pepsin and rennin, are present. Renin acts on milk, and pepsin converts protein to peptones. The thick liquid formed(chyme) now passes to the duodenum.
3. Small intestine

Duodenum: Here, the pancreas secretes pancreatic juice, which contains three digestive enzymes, i.e.

1. Amylase – Converts starch to maltose
2. Lipase – Converts fats and oils to fatty acids and glycerol
3. Trypsinogen – Converts protein and peptones to polypeptides

 

The digestion of fats and oils is aided by bile. Bile helps in the emulsification of fats. At the duodenum, the food, now in liquid form, called chyme, 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 – converts fats and oils to fatty acids and glycerol
2. Erepsin – Converts polypeptides to amino acids
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 of the digestion of protein is amino acid, starch is glucose and fats and oil is fatty acid and glycerol.

 

EVALUATION

1. What are non-ruminant animals?
2. List the digestive enzymes in A. stomach, B. small intestine, C. pancreas, D. liver and their functions.

 

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 with the beak. The food then passes on to the crop through the oesophagus.

The food is stored temporarily in the crop, where moistened and fermented by some bacteria. The food now passes on to the proventriculus (glandular stomach), where digestive juices such as pepsin and amylase are 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 take place. The undigested food materials are removed from the digestive tract as faeces.

 

DIFFERENCES BETWEEN MONOGASTRIC AND POLYGASTRIC ANIMALS

S/N	MONOGASTRIC	POLYGASTRIC
1.	It cannot ruminate or chew cud	It can ruminate or chew cud
2.	Feed is mainly basal and concentrated food	Feed is mainly grasses and other cellulose
3.	It cannot digest cellulose and fibre properly	Possesses four stomach compartments
4.	It can digest cellulose and fibre very well	It cannot synthesise its protein
5.	Digestion is not aided by bacteria	Digestion is aided by bacteria
6.	It can synthesise its protein	It cannot synthesise its own protein

 

EVALUATION

1. Describe briefly the digestion in domestic fowl.
2. Differentiate between ruminant and non-ruminant animals.

 

CIRCULATORY SYSTEM

The circulatory system consists of all the tissues and organs that are involved in the transportation of materials through the blood around the body of farm animals. Farm animals possess a closed circulatory system.

This means that oxygenated and deoxygenated blood do not mix. They also display a pattern of double circulation(this means 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-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 and no nucleus when matured, contain iron pigment called haemoglobin that helps to transport oxygen, produced in bone marrow,
4. White blood cells (Leucocytes): irregular in shape, fewer 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 the body against germs via leucocytes
6. Platelets help in blood clotting
7. Transport 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 vessels, they are:

1. Artery: carries blood away from the heart to another part 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 venous.
3. Capillaries: tiny bloods vessel around tissues and organs where arteries and veins meets.

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 parts of the heart, called the septum. The auricles and ventricles are divided on the right by a tricuspid valve and on the left by a mitral/bicuspids valve.

EVALUATION

1. What is the circulatory system?
2. List the functions of blood.

REPRODUCTIVE SYSTEM OF FARM ANIMALS

Reproduction is the biological process that gives rise to new organisms (offspring) from their parent. This includes all the organs and tissues concerned with reproduction in animals. Reproduction is the ability of animals to give birth to young ones.

The purpose of reproduction is to ensure the continuity of life. Farm animals reproduce sexually and are mostly viviparous (give birth to live form of their young). Poultry birds and fish are oviparous (they both lay eggs and poultry brood over theirs, while fish do not).

Fertilisation in most farm animals is internal, external in fishes and hormones play an important role in the processes of reproduction as well as in the development of sex-inhibited characters.

MALE REPRODUCTIVE SYSTEM

The male reproductive system includes the testes, which produce the spermatozoa and a sex hormone called testosterone, which aids the development of male secondary sexual characteristics.

The spermatozoa are produced in the testes or testicles by a process called Spermatogenesis. The testes may be suspended (as in cattle, sheep and goat) and are protected by the scrotal sac (scrotum) outside the abdominal cavity to enable the sperm cells to be produced at the desired temperature.

The epididymis ensures the storage and maturation of sperm cells in the testes, i.e. stores sperm until they are matured. The testes are connected to the uterus masculinus by the vas deferens, which transports sperm from the testes to the uterus masculinus, where mature spermatozoa are stored until they are released during mating.

Attached to the side of the urethra are accessory glands, i.e. Cowper’s gland, also called the bulbourethral gland, seminal vesicles and prostate gland, which produce a slimy alkaline fluid which aids the movement of spermatozoa. The fluid together with spermatozoa results in the formation of semen, the urethra is an uro-genital organ which helps to inject sperms into the vaginal as well as the removal of urine. The urethra ends externally in penis.

FEMALE REPRODUCTIVE SYSTEM

The female reproductive system consists of a pair of ovaries that produce egg cells or ova and fallopian tubes where fertilisation occurs and which transport the fertilised ovum to the uterus.

The uterus is the place in the female reproductive system where the growth of fthe etus takes place. The cervix separates the uterus from the vagina or birth canal. The entire system ends with the vulva (labia majora and minora) to the external.

Vagina is a fibro muscular tube of 7.5 to 10cm in length, situated anterior to the rectum and anal canal and posterior to the bladder and urethra. It is the organ of copulation, deposition of semen, and exit from the uterus during parturition.

The accessory organ of the female reproductive system includes outermost portion of the vagina (vestibule). The Cowper’s glands, also called Bartholin’s gland, are 1.5 to 2.0cm in length located above the perineal gland. It secretes mucus to provide vaginal lubrication.

EVALUATION

1. What is reproduction in farm animals?
2. Name the accessory glands located along the urethra in male animals.

 

GENERAL EVALUATION

1. Describe the female reproductive system.
2. What are the similarities between monogastric and polygastric animals in the area of digestion?
3. What are the main components of the circulatory system?

 

WEEKEND ASSIGNMENT

1. The stomach of ruminant animals is made up of the following, except A. gizzard, B. reticulum, C. abomasum, D. manyplies
2. Digestion of food starts in a farm animal from A. the mouth, B. the caecum, C. the small intestine
3. stomach
4. Which of these is not part of the male reproductive organs? A. testes, B. oviduct
5. epididymis D. vas deferens

1. The part of the female reproductive system responsible or lubricating the vaginal is known a ____ A. mucus B.perineal gland C.cowper’s gland D. epididymis
2. ____ is a major constituent of blood A. Haemoglobin B. WaterC. CalciumD. Serum

 

THEORY

1. Describe digestion in a named polygastric animal.
2. Differentiate between monogamous and polygamous animals.
3. What are sphincters?

 

See also

Definition and Objectives of Export Promotion in Agriculture

Benefits of Export Promotion

Agricultural Insurance | Meaning, Importance, Types, Risks, Problems & Terminologies

Agricultural Marketing | Co-operative Societies, Producers, Middlemen, Wholesalers,

Farm Records and Farm Accounts