Farm animal biological systems Pack 5 Digestion in non-ruminants Pack Code: ABS05 This pack you will help you to: explain the function of the major types of digestive system. list the main parts of the major types of digestive system. www.lbcnc.org.uk understand the differences between ruminant and non ruminant digestive systems.
About this pack Objectives When you have completed this pack you should be familiar with the function and main features of the major types of digestive system. The pack will help you to: explain the function of the major types of digestive system list the main parts of the major types of digestive system understand the differences between ruminant and non ruminant digestive systems. The pack is also relevant to the level 3 unit Understand Animal Anatomy and Physiology, and in particular to: Outcome 1: Know the structure and functions of biological systems in animals Outcome 4: Understand how an animal s body structure and systems are adapted to its environment. It is also relevant to the level 3 unit Understand the Principles of Animal Nutrition, and in particular to: Outcome 1: Understand the functions of the main components of an animal s diet Links to other packs This is one of a series of learning packs, each tackling an aspect of farm animal biology. They are: ABS1: The skeleton ABS2: Joints ABS3: Circulation ABS4: Respiration ABS5: Digestion in non-ruminants ABS6: Digestion in non-ruminants ABS7: Digestion in horses ABS8: The reproductive system ABS9: Oestrus and hormones ABS10: Gestation and birth ABS11: How animal cells work ABS12: How animal cells divide ABS13: Connective and epithelial tissue ABS14: Muscle and nervous tissue ABS15: Sensory organs ABS16: Introduction to genetics ABS17: Meiosis ABS18: Inheritance ABS19: Selective breeding ABS20: Breeding technology ABS21: The lymphatic system ABS22: The endocrine system ABS23: The nervous system Farm animal biological systems 2
Overview of the digestive system Food contains both useful elements such as carbohydrates, proteins, oils (fats if animal in origin), minerals and vitamins and waste elements which the body is unable to digest and use. The digestive system separates the useful components from the waste. The purpose of the digestive system is to: mechanically and chemically digest food breaking down complex food substances into simpler substances allow the absorption of food through the wall of the digestive tract and into the blood assimilation using the simple products of digestion for maintaining the body, growth, milk production and pregnancy. assist the elimination of solid waste : Substances that are not used by the body after they have been absorbed will be removed by excretion through perspiration and urination. Substances that are not digested are removed by egestion, for example, dung. The digestive system has muscles running along its entire length. These help to move and churn up the food. Digestion is also helped by other organs, such as the liver, that produce chemicals to break down the food. The digestive tract The digestive tract is a continuous tube running from the mouth to the anus. This is where the process of digestion takes place. The main parts of the digestive tract are the: mouth or buccal cavity oesophagus stomach small intestine linked to the: gall bladder liver pancreas large intestine including colon, caecum and rectum anus. Farm animal biological systems 3
Two types of digestive system There are two types of digestive system, ruminant and non-ruminant. The differences between them are mainly in the stomach: ruminants have a complex system of four stomachs that are capable of digesting complex roughage (plant material) into starches and sugars which can then be used by the animal. Cows and sheep are ruminants non-ruminants have a more simple system such as that found in pigs (and humans) where only one stomach is present. Review quiz 1 Which of these diagrams shows a simple or non-ruminant and which shows a complex or ruminant digestive system? Picture 1 Picture 2 The answer is at the end of this pack. This pack looks at the simple stomach. Farm animal biological systems 4
The function of the mouth and teeth Food digestion starts with the mouth. The mouth grasps, grinds and chews food. This is an important part of mechanical digestion. Prehension Gathering food ready to be put into the mouth is termed prehension. Humans have hands which we use to gather food; they are our organs of prehension. Farm animals do not have hands, and can be divided into three groups 1 The graspers 2 The nibblers 3 The gobblers A cow is a grasper. Next time you are in a field with cows watch them graze. The tongue is covered in many papillae (projections) which give it a rough feel. It comes out, grasps the grass and pulls it back over the incisor teeth into the mouth. Because they use a pulling action, cattle can do a lot of damage to a new ley. As the roots are young and shallow, anchoring is poor and the plants can easily be pulled out of the ground. Sheep are nibblers using the incisors and the dental pad. This gives a much gentler action on the pasture. The grass is nibbled off very close to the ground. This is a milder action then the grasping of cattle and encourages tillering of the sward, ideal for a new ley. Pigs are gobblers. Their shovel like lower jaw is designed to root and scoop. They can cause tremendous damage to pastures unless they are ringed. Teeth The teeth are the hardest structures in the animal body. They cut, shear and grind the food. There are four types of teeth: Incisors or broad teeth (the front teeth) used for nibbling and shearing, found in all animals Canine, dog or eye teeth used for tearing, found in humans, pigs, dogs etc, but not found in ruminants Premolars used for grinding, found in all animals Molars used for grinding, found in all animals. Farm animal biological systems 5
Activity Why does the animal need to grind up its food? The answer is at the end of this pack. Chewing Chewing is the mechanical breakdown of food using the teeth, tongue and cheek muscles. Chewing reduces the physical size of the food making it easier to swallow and easier to chemically digest in the digestive tract. Why does chewing speed digestion? Chewing breaks the food down into smaller chunks, and in doing so increases the surface area of the food. Farm animal biological systems 6
Activity Measure the total distance around the bottom four lumps and compare it to the distance around the top lump. Check your answer with the one at the end of this pack Imagine the top lump is a piece of food before chewing and the bottom four is the food after chewing. Although the total amount of food is the same, the chewed food has double the surface area. An increased surface area gives a bigger surface for digestive chemicals or bacteria to act on and so increases the speed of digestion Saliva Saliva produced in the mouth is the first of the digestive juices. Saliva is a fluid produced by salivary glands in the mouth. Its functions are to: to lubricate the food, and make it easier to swallow to dissolve chemicals in the food to stimulate the taste buds. Swallowing Swallowing involves the tongue moving up and back, pushing the food into the pharynx (throat) where muscles contract pushing the food into the oesophagus. The oesophagus is a muscular tube leading from the throat to the stomach. Once food enters the oesophagus the muscles contract (peristalsis) forcing the food along into the stomach. Farm animal biological systems 7
Review quiz 2 1 Which of the following would be best suited to grazing a new grass ley:! a) cows! b) pigs! c) sheep 2 Which of the teeth listed below are used for grinding the food?! a) canine! b) molars! c) incisors The simple stomach Structure of the stomach The simple stomach is present in monogastric animals such as pigs and humans. The last part of the ruminant stomach (the abomasum) is also very similar to the simple stomach. The stomach is a bag which lies between the oesophagus and the small intestine. It is used to store, digest and acidify food. Part of the stomach is glandular, which means that it has structures (glands) which produce and secrete digestive juices. This is where chemical digestion starts. Food entering the stomach is gradually mixed with the food already present and the gastric juices. The stomach walls are protected from the digestive enzymes by a thick layer of mucus. Gastric juice Gastric juice contains hydrochloric acid, pepsin and bacteria. The gastric juice of young animals also contains rennin, which helps digest milk. All of these play an important part in digestion, and their function is explained below. Farm animal biological systems 8
Hydrochloric acid The action of hydrochloric acid gradually reduces the ph of the food to around ph 2. This is not instantaneous and can take from two to twelve hours after feeding. One of the functions of the acid is to kill bacteria which are taken in with the food. Since it takes several hours for all the food to become acidic it is possible for bacteria to enter the small intestine and cause disease. This is one reason why good feeding management is so vital. Pepsin This is an enzyme which starts off the digestion of protein into smaller chains called peptides. Pepsin is produced in an inactive form called pepsinogen and changed to pepsin by the action of hydrochloric acid. Enzymes are produced by glands, and sometimes need to be released in an inactive form to prevent the glands from self-digesting. Bacteria There are bacteria in the stomach, as in the rest of the gut. The bacteria (lactobacilli) ferment food, producing organic acids such as Lactic acid. These bacteria are essential to the well being of the gut. Rennin Rennin is found in the stomachs of young animals. It coagulates milk into curds (solids) and whey (liquid). Coagulation of milk reduces the speed at which it leaves the stomach and this allows hydrochloric acid and pepsin to have their full effect. The whey leaves the stomach very quickly, but the curd is gradually digested by the pepsin. Leaving the stomach When the food has been digested and the top part of the small intestine (called the duodenum) is empty, a valve at the bottom of the stomach called the pyloric sphincter opens. The food, now called ëchymeí, is forced out of the stomach through this valve and enters the small intestine. Farm animal biological systems 9
Review quiz 3 1 Hydrochloric acid acts to:! a) reduce the ph of food! b) increase the ph of food! c) allow bacteria to breed 2 Rennin is found in the gastric juice of all animals! True! False 3 After the food leaves the stomach it enters:! a) the large intestine! b) the small intestine! c) the oesophagus The intestines The intestines are long tubes running from the stomach to the anus. They are divided into two parts: the first part is the small intestine is thin but very long in the pig it is about 18 metres! The primary function of the small intestine is to absorb useful materials from food. the second part is the large intestine is wider but shorter. The primary function of the large intestine is to absorb water and so prevent it being lost from the body in the faeces. Rectum Stomach Oesophagus Caecum Large intestine Colon Pyloric sphincter Duodenum Jejunom Ileum Small intestine Farm animal biological systems 10
The small intestine The small intestine is made up of the duodenum, the jejunum and the ileum. In the duodenum Brunner s glands secrete alkaline fluid, neutralizing the acid from the stomach to about ph 7-8, at which level digestive enzymes can function properly. The duodenum also connects to three organs which secrete chemicals needed for digestion: The liver produces bile and the gall bladder concentrates and releases this. Bile emulsifies fats, turning them into many smaller droplets. This increases the surface area for the fat digesting enzyme, lipase, to act on. The pancreas produces specialized enzymes including lipase to digest fats and tripsin to digest proteins. These break the food down into parts small enough to be absorbed through the intestine walls. Food passes through the jejunum into the next section of the small intestine, the ileum. This is where most absorption occurs, as sugars, amino acids, vitamins and minerals are absorbed into the bloodstream. This cross section shows how a series of layers of tissue in the ileum surround the lumen the space through which food passes. Mucosa with villi and lacteals The lumen Submucosa with nerves and blood vessels Serosa Longitudinal muscle layer Circular muscle layer Muscle contraction keeps food moving The ileum is lined with mucosa. This has many small projections villi which increase the surface area for absorbing nutrients. They also contain lacteals lymphatic capillaries that help absorb fatty acids and glycerols. Nutrients pass through the mucosa to the submucosa, where they are absorbed into blood vessels and can pass into the blood. The submucosa also contains nerves which help coordinate digestion. After this there are layers of muscle tissue, Waves of muscle contraction move food down the intestine. This action is known as peristalsis. Finally a further layer of tissue is called the serosa. High oil diets can produce soft body fat. This is why oily feed should be restricted in the final ration of meat producing animals. Farm animal biological systems 11
Review quiz 4 1 Bile is secreted from:! a) the stomach! b) the gall bladder! c) the pancreas 2 The function of bile is to:! a) digest fats! b) neutralise acid! c) emulsify fats 3 Most absorption by the small intestine occurs in:! a) the ileum! b) the duodenum! c) the jejunum Check your answers at the end of this pack. The large intestine The food passes through a valve called the ileocaecaecal sphincter into the large intestine. The large intestine is named because of its width not its length. Most of the water and any remaining nutrients are absorbed in the large intestine. The large intestine is made up of two parts: The caecum contains microorganisms which digest highly fibrous material for absorption. The caecum is particularly large in non-ruminant herbivores such as horses, rabbits and hamsters. The colon removes any remaining water in the food. Rectum and anus Having passed through the caecum and colon, the remaining waste material then passes into the rectum, which acts as a storage space. When the rectum is full, a sphincter opens and allows the remaining waste material to be ejected through the anus. The breakdown of proteins, which contain nitrogen, produces ammonia which is toxic. Mammals convert it into urea which is excreted by the kidneys. Birds and reptiles convert it into uric acid a process which needs less water but uses more energy. Farm animal biological systems 12
Answers to review quizzes Review quiz 1 Picture 1 shows a ruminant, while picture 2 shows a simple digestive system. Review quiz 2 1 C. Sheep are ideal for a new ley as they nibble the grass off very close to the ground. 2 B. Molars are for grinding. Review quiz 2 1 A. Hydrochloric acid reduces ph 2 False. 3 B. The small intestine. Review quiz 3 1 B. The gall bladder secretes bile. 2 C. Bile emulsifies fats. 3 A. Most absorption occurs in the ileum. Answer to activity on page 6 There are two reasons why an animal needs to grind up its food: to produce bits of food small enough to be swallowed easily to increase the surface area of the food. This means there is a greater area to absorb and be affected by digestive chemicals. Answer to activity on page 7 The distance around the top lump is 12cm, whereas the total distance around the bottom four is 6x4cm = 24cm. Farm animal biological systems 13
Further reading R. D. Frandson, Anatomy and Physiology of Farm Animals (6 th Ed). Lippincolt, Wiley Blackwell, 2003 D.R. Lane and B Cooper, Veterinary Nursing (3 rd Heinemann, 2003 edition). Butterworth William O Reece, Functional Anatomy and Physiology of Domestic Animals (3 rd Ed) Wiley Blackwell, 2004 Glossary Buccal Cavity Caecum Colon Duodenum Echymel Ileocaecal sphincter Ileum Jejunum Monogastric Oesophagus Peristalsis Pyloric sphincter Ruminant The mouth Part of large intestine Part of large intestine First part of small intestine Food leaving the stomach Valve between small and large intestine Third part of small intestine Second part of small intestine Animal with a simple stomach e.g. pig Tube leading from mouth to stomach Muscle action which moves food through the digestive tract Valve at bottom of stomach Animal with a complex stomach e.g. cow Farm animal biological systems 14
Knowledge quiz 1 What is the term for the continuous tube that runs from the mouth to the anus? 2 What is the main difference between ruminants and non-ruminants? 3 How do the teeth aid digestion? 4 Name the three parts of the small intestine. 5 What is the term for the waves of muscle contraction which move food along the small intestine? 6 Why does the acid from the stomach need to be neutralised? 7 What does the colon do? 8 Where does the waste material go after it has left the large intestine? 9 What structures line the ileum and help to maximise absorption? Farm animal biological systems 15
Acknowledgements This learning pack has been produced by the Land Based Colleges National Consortium Ltd. The LBCNC is a consortium of colleges working in the land-based sector which cooperate in the development and production of quality flexible learning materials which encourage independent learning. We would like to acknowledge the contributions made by the following individuals and colleges in the development of this learning pack. Initial source material and guidance Source material was provided by: Eirwyn Jenkins, Hartpury College Paul Attard and Peter Edwards, Walford College Graham Corner, Cannington College Developed and produced for LBCNC by Learners First Illustrations: Shevanthi De-Silva Revised in July 2011 2011 The Land Based Colleges National Consortium Ltd. All rights reserved. Permission to photocopy or adapt the material in this learning pack is granted to members of the Land Based Colleges National Consortium Ltd. only. For further information please contact the LBCNC project management team at 7 Tyne Road, Bishopston, Bristol BS7 8EE. Tel 0117 942 3504 Farm animal biological systems 16