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The following sources are acknowledged for using their information: ➢ Study and master agricultural sciences grade 12 ➢ Focus on agricultural sciences grade 12 Almost all the information in the notes was compiled using the above-mentioned sources for the Mambane secondary school grade 12 learners. Therefore, the notes are NOT FOR SALE. I the compiler apologise for any errors or omissions and invite copyright holders to contact me if any have occurred, so that we can rectify them.
Comparison of external structure of the alimentary canal of ruminants and non- ruminants Ruminants Non-ruminants ➢ Polygastric ➢ Monogastric ➢ Complex stomach ➢ Simple stomach ➢ Digest food with high quality fibre and cellulose ➢ Cannot digest food with high quality fibre and cellulose ➢ Chew their food partially, regurgitate later and re-chew. ➢ Chew their food properly and swallow it once Figure 1.1.2 the external structure of the alimentary canal of a goat Figure 1.1.3 the external structure of the alimentary canal of a cow
Figure 1.1.4 the external structure of the alimentary canal of a pig Figure 1.1.5 the external structure of the alimentary canal of a fowl
Peristalsis is the involuntary contraction and relaxation of muscles that pushes food through the alimentary canal ➢ Peristalsis occur in the oesophagus, stomach and intestines ➢ If the rate of peristalsis increases , food will move faster along the alimentary canal and less fluid will be absorbed leading to Diarrhoea ➢ If the rate of peristalsis decreases , food will move slower along the alimentary canal and more fluid will be absorbed leading to Constipation Retro-peristalsis Retro-peristalsis is the involuntary contraction and relaxation of muscles that pushes food back to the mouth in the alimentary canal
2. PHARYNX Pharynx is the funnel-shaped muscular tube connecting the mouth cavity to the digestive and respiratory systems. It is enclosed by the epiglottis to prevent food from entering the trachea during swallowing. Functions of the pharynx ➢ Exchange of gases ➢ Allows for the passage of food from the mouth to the oesophagus ➢ Connects the mouth to the oesophagus 3. OESOPHAGUS/GULLET Oesophagus is a tube-like structure that extends from the back of the throat (pharynx) to the stomach. There is no absorption of nutrients in the oesophagus. Functions of the oesophagus ➢ Connects the mouth to the stomach ➢ Allows the passage of food to the stomach ➢ Contain mucous membranes that secrete mucus which lubricates the food for easy passage. CROP Crop is the enlarged extension of the oesophagus where food is stored, moistened and softened in fowls. There is no absorption of nutrients in the crop. Functions of the crop ➢ Stores the food ➢ Moistens and softens the food
Stomach is a pear-shaped, sac-like structure that store and chemically digest the food. Stomach of the pig Functions of the stomach ➢ Stores food temporarily ➢ Chemically digest the food ➢ Secretes mucus that protects it from acidity Stomach of the fowl PROVENTRICULUS Functions of the proventriculus ➢ Secrete digestive juices ➢ Chemically digest the food VENTRICULUS / GIZZARD Functions of the ventriculus/gizzard ➢ Store food ➢ Grinds the food by small stones (mechanical digestion) STOMACH OF THE RUMINANT Figure 1.1.7 Stomach of the ruminant The stomach of a ruminant consists of 4 chambers or parts; Rumen , Reticulum , Omasum and Abomasum. The first 3 chambers; Rumen, Reticulum and Omasum are known as forestomachs. Rumen and reticulum function as a unit, which is called Reticulorumen.
Functions of the reticulum ➢ Traps foreign objects such as wires, nails and stones ➢ Forms boluses for regurgitation and rumination ➢ Acts as a filter Omasum The omasum has leaf-like folds (like the pages of a book). The folds increase the surface area for absorption of moisture from the ingested feed The inner wall of the omasum is covered with Papillae that increase the surface area FIGURE 1.1.10 The omasum ➢ Acts as a temporary storage site and filter ➢ Sends large food particles back to the reticulorumen ➢ Break down large food particles into smaller particles Abomasum Abomasum is a true or glandular stomach Abomasum is the compartment of the ruminant stomach that corresponds to the simple stomach of a pig. Enzymatic digestion starts in the abomasum. Secrete hydrochloric acid which makes it to be more acidic. FIGURE 1.1.11 The abomasum
Functions of the abomasum ➢ Secretes digestive juices, hydrochloric acid and digestive enzymes ➢ Sends chyme to small intestines ➢ Break down food particles into simple molecules, by chemical digestion
5. SMALL INTESTINES Small intestine is a long coiled tube that is divided into 3 parts; Duodenum , Jejunum and Ileum. Small intestines is the longest section of the alimentary canal Its length increases the surface area for absorption of digested feed Small intestines are also folded to increase the surface area for absorption Finger-like projections called villi increase the surface area for absorption Contraction and relaxation of the walls of the small intestines by peristalsis forces food to move across the small intestines Figure 1.1.12 villi in the small intestines VILLI Villi are small finger-like projections of the small intestines It consists of; Blood capillaries, Lacteal, Gland of lieberkuhn, lymph vessel and micro villi
Functions of the large intestines ➢ Reabsorption of water in the faecal material by the caeca ➢ Dehydration of ingested matter by the caeca ➢ Fermentation of remaining available nutrients, by colon ➢ Provision of a suitable environment for bacteria to grow and reproduce by the colon ➢ Storage of undigested food by rectum ➢ Secretion of mucus to lubricate and make the passage of waste easier
7. ANUS ➢ Anus eliminates waste in the form of faeces Cloaca/vent ➢ Cloaca/vent is a common opening for both digestive and urinary systems in fowls DIGESTION Digestion is the process whereby food molecules are broken down into small particles. Digestion starts in the mouth There are two types of digestion namely; Mechanical and Chemical digestion ➢ Mechanical digestion is the physical breakdown of large food molecules into smaller molecules, e.g. Chewing, grinding, and churning ➢ Chemical digestion is the breakdown of food by chemical reactions such as hydrochloric acid and digestive juices Saliva Saliva is a thin, colourless, watery and slightly alkaline liquid Saliva contains enzyme salivary emylase Saliva is secreted by salivary glands in the mouth Three pairs of salivary glands ➢ Sublingual glands found underneath the tongue and lower jaws ➢ Submandibular glands located at the angle of the lower jaw ➢ Parotid glands found below the ears
Three pairs of salivary glands Functions of saliva ➢ Moistening of the food and mouth ➢ Secretes ptyalin containing enzyme salivary emylase ➢ Solvent for dry food ➢ Neutralises acidity Functions of hydrochloric acid ➢ It is anticeptic ➢ Break down food into simple soluble substances ➢ Neutralises alkaline reaction of saliva ➢ Changes the PH of the stomach into acid medium Functions of enzymes ➢ Pepsin converts proteins to peptides ➢ Rennin converts soluble caseinogen into insoluble casein. This means it curdles milk ➢ Gastric lipase converts fats into glycerol and fatty acids ACCESSORY DIGESTIVE ORGANS
**1. Liver
2. Pancreas Pancreas is a gland located between the stomach and small intestines It contains both endocrine and exocrine tissues ➢ Exocrine pancreas secretes pancreatic juice ➢ Endocrine pancreas is also known as islets of Langerhans, and secretes hormones Endocrine pancreas/Islets of Langerhans ➢ Secrete hormone insulin and glucagon directly to the blood stream ➢ Insulin stimulates the conversion of glucose to glycogen ➢ Insulin promotes the movement of glucose and other nutrients out of the blood into the cells to be used as energy ➢ Glucagon promotes the movement of glucose into the blood into the blood when glucose levels are low ➢ Glucagon breaks down glycogen to glucose Functions of pancreas ➢ Secretes pancreatic juice ➢ Secrete hormone insulin and glucagon 3. Intestinal glands Example of intestinal gland is Glands of Lieberkuhn The Glands of Lieberkuhn are found throughout the small intestines between the villi. Function of Glands of Lieberkuhn ➢ Secretes duodenal juice (succus intericus) Brunner’s glands/Duodenal glands Brunner’s glands are located in the Duodenum Functions of Brunner’s glands/Duodenal glands ➢ Produce alkaline secretion rich in mucus ➢ Protects the duodenum from acidic chyme ➢ Lubricates the walls of the small intestines
Rumination (chewing the cud) Rumination is when food is chewed, swallowed, brought back to the mouth (regurgitation) and chewed again. Rechewing reduces the food particles size and makes it easier for micro-organisms in the rumen to digest fine particles. Rumination stimulates the secretion of saliva which is necessary for fermentation in the reticulorumen. The saliva of ruminants does not contain the enzyme salivary emylase Rumination normally takes place when the cattle is resting and not eating Rumination consists of four processes; Regurgitation , Remastication , Re- swallowing and Eructation. The process of rumination The path of food in the stomach of the cow during rumination ➢ Ruminants chew their food partially, roll it into bolus and swallow ➢ The food moves via the oesophagus by the process of peristalsis and stored in the rumen (and reticulum) ➢ In the reticulum, the food is separated into digestible material and non- digestible material (such as stones and nails) ➢ The undigested food in the reticulorumen is regurgitated back to the mouth by retro-peristalsis to be remasticated, re-chewed thoroughly and re-swallowed ➢ Very fine particles pass into the omasum and ends up in the abomasum
➢ Abomasum secretes rennin which curdles milk and slow it down to allow time for digestion ➢ Immature ruminants should not be fed non-protein nitrogen feeds such as urea ➢ The calve will only become a real ruminant when it is three to four months old ➢ Microorganisms only become established in the rumen when the young ruminant starts to eat solid food ➢ The development of rumen and reticulum is triggered by volatile fatty acids produced during fermentation of hay or grain ➢ Rumen microorganisms are obtained from the mother or environment ➢ The rumen gradually increases in size and starts to function its digestive processes ➢ The oesophageal groove disappears and the animal become a fully functional ruminant REQUIREMENTS FOR NORMAL FUCTIONING OF RUMEN MICROBES ➢ Oxygen-free environment ➢ The presence of carbon dioxide ➢ Neutral PH ➢ Regular intake of feed ➢ Osmotic condition ➢ Sufficient nutrients FUCTIONS OF RUMEN MICROBES ➢ Digestion of cellulose and hemicellulose ➢ Hydrolysis of protein ➢ Synthesis of vitamins ➢ Synthesis of amino CONTENTS OF THE RUMEN FIGURE 1.3.4 the contents of the rumen
The following substances are found in a rumen: ➢ Gases (mainly carbon dioxide and methane) ➢ The grain and roughage of the previous day ➢ The new roughage THE END PRODUCTS OF MICROBIAL FERMENTATION ➢ Volatile fatty acids such as acetic acid , propionic acid and butyric acid ➢ Ammonia ➢ Gases (mainly carbon dioxide and methane) ABSORPTION OF FOOD IN THE RUMEN INTO THE BLOODSTREAM ACTIVE TRANSPORT Active Transport is the movement of nutrients against the concentration gradient. ➢ During active transport, molecules move from an area of lower concentration to an area of higher concentration. ➢ Energy is needed for active transport ➢ Energy is supplied by ATP (adenosine triphosphate). PASSIVE TRANSPORT Passive Transport is the movement of nutrients along the concentration gradient. ➢ During passive transport, molecules move from an area of higher concentration to an area of lower concentration.
