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Agricultural Science

DIGESTIVE SYSTEM

  • Digestive system and digestion
  • Digestion in ruminant (polygastric) animals
  • Digestion in non-ruminant (monogastric) animals
  • Digestion in poultry birds
  • 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 fore stomach (honey comb), omasum(the fardel, manyplies or psalterium) and abomasum (true stomach). These animals can ruminate or chew the cud. Exampleof farm animals having this stomach compartment includes cattle, sheep, goat etc.

 

Cattle for example when feeding gather 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 oesophagus and enter the rumen, where digestion of cellulose by bacteria takes place.

DIGESTION IN RUMINANT ANIMALS

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, 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.

 

EVALUATION

  1. What are ruminant animals? Give five examples.
  2. Describe briefly 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 fibers 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 area 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 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

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 oil to fatty acid and glycerol
  3. 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

DIGESTION IN NON-RUMINANT ANIMALS

The end product in 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

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 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 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 takes 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.        Possess one stomach compartment Possess four stomach compartment
4.        It cannot digest cellulose and fiber properly It can digest cellulose and fiber very well
5.        Digestion is not aided by bacteria Digestion is aided by bacteria
6.        It cannot synthesis their own protein It can synthesis their own protein

 

EVALUATION

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

 

CIRCULATORY SYSTEM

Circulatory system consists of all the tissues and organs that are involved in the transportation of materials through the blood round the body offarm animals. Farm animals possess 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.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 andblood Cells, which are;

  1. Plasma-liquid part of the blood. It contains water, blood proteins (e.g fibrinogen),dissolved mineral salt, waste product, digested food.
  2. The Blood Cells(corpuscles)
  3. Red blood cells (Erythrocytes): biconcave, circular in shape 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, few than red blood cells, have 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 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 cell.
  8. Maintain water level and turgidity of the body

 

THE BLOOD VESSELS

These are a network ofspaces in the body through which material are movedfrom 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 part of the body. It further divides into arterioles.
  2. Vein: this vessel caries blood back to the heart from other parts of the body. It further divides to form veinous.
  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 round the body. Each pump action of the heart isknown a heartbeat. The heartis located in the thoracic cavity of the body, protected by the pericardium. It consists offour 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.

 

EVALUATION

  1. What is 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 animal. Reproduction is the ability of animals to give birth to young ones. The purpose of reproduction is to ensure continuity of life. Farm animals reproduce sexually and mostly viviparous (given birth to life form of their young). Poultry birds and fishes are oviparous (they both lay eggs and poultry brood over theirs while fishes do not). Fertilization in most farm animals is internalbut 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 include the testes which produces the spermatozoa and sex hormone called testosterone which aid the development of male secondary sexual characters. The spermatozoa are produce in the testes or testicles by a process called Spermatogenesis. The testes may be suspended (as in cattle, sheep and goat) and is protected by scrotal sac (scrotum) outside the abdominal cavity to enable the sperm cells to be produced at desired temperature. The epididymis ensures the storage maturation of sperm cells in the testes, i.e. store sperms until they are matured. The testes are connected to the uterus masculinus by vas deferens which transports sperms from 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 bulbourethral gland, seminar vesicles and prostate gland which produces 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.

Male Reproductive Organ

Male reproductive system of farm animals

 

FEMALE REPRODUCTIVE SYSTEM

The female reproductive system consist of a pair of ovaries that produces egg cells or ova and fallopian tubes where fertilization occurs an which transports the fertilized ovum to the uterus. The uterus is the place in the female reproductive system where the growth of foetus 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 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 is 1.5 to 2.0cm in length located above the perineal gland. It secretes mucus to provide vaginal lubrication.

FEMALE REPRODUCTIVE SYSTEM FEMALE REPRODUCTIVE SYSTEM1

The female reproductive system

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 of monogastric and polygastric animals in the area of digestion?
  3. What are the main components of circulatory system?

 

WEEKEND ASSIGNMENT

  1. Stomach of ruminant animals is made up of the following except A. gizzard B. reticulum C. abomasum  D.manyplies
  2. Digestion of food start in farm animal from A. mouth B. caecum C. small intestine
  1. stomach
  1. Which of these is not part of the male reproductive organ A. testes B. oviduct
  1. 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.HaemoglobinB. WaterC. CalciumD. Serum

 

THEORY

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

 

See also

FARM MECHANIZATION

FARM POWER

SIMPLE FARM TOOLS

PROBLEMS OF FARM MANAGER

MANAGEMENT

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