Here is a term paper on ‘Animal Nutrition’ for class 9, 10, 11 and 12. Find paragraphs, long and short term papers on ‘Animal Nutrition’ especially written for school and college students.
Term Paper on Animal Nutrition
Term Paper Contents:
- Term Paper on the Introduction to Animal Nutrition
- Term Paper on the Problems Caused by an Unbalanced Diet
- Term Paper on the Human Alimentary Canal
- Term Paper on the Functions of the Main Regions of the Alimentary Canal
- Term Paper on the Summary and Need of Chemical Digestion in the Alimentary Canal
- Term Paper on Teeth and the Part they Play in Mechanical Digestion
- Term Paper on the Importance of Proper Tooth Care
- Term Paper on the Absorption and Assimilation of Food
- Term Paper on the Role of the Liver in Glucose and Amino Acid Metabolism
Term Paper # 1. Introduction to Animal Nutrition:
Plants manufacture their own food (they are autotrophic). Animals cannot, so they obtain their food requirements ‘second-hand’ either by eating plants or by eating other animals which have eaten plants. Animals are heterotrophic (‘hetero’ = other, ‘trophic’ = feeding).
However, for the animal to be healthy, its diet must be in their correct amounts. A diet which has the correct amount of each constituent is called a balanced diet.
A balanced diet is different for each person, and depends on their lifestyle, age and sex.
The (basal) metabolic rate of males is higher than that of females. If a man and a woman are involved in identical activities, the man will therefore require more energy from his diet.
Fats provide the greatest amount of energy per unit mass – just over twice as much as carbohydrates and proteins. For this reason, an individual who eats a diet rich in fats is likely to become obese (over-weight). The amount of energy contained within the foods they consume is much larger than the energy they use up.
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2. Problems Caused by an Unbalanced Diet:
A person’s diet may be unsuitable for healthy growth for two main reasons:
A. The balance of constituents is incorrect – leading to malnutrition.
B. There is insufficient quantity – leading to starvation.
A. Malnutrition:
i. Constipation,
ii. Heart disease and
iii. Obesity are three of the most important effects of malnutrition.
i. Constipation:
It is a result of insufficient fibre in the diet (see the section on nutrients, below). A diet lacking in fibre may, over several years, lead to bowel cancer.
ii. Heart Disease:
It can occur when animal fats and cholesterol form deposits called atheroma on the walls of the coronary artery, the vessel that carries blood to the heart muscle. Atheroma forms a blockage (occlusion) in the artery and restricts blood flow, decreasing oxygen supply to the heart muscle. In severe cases, the artery may become blocked, leading to a cardiac arrest (heart attack).
Atheroma decreases the bore (diameter) of the arteries and thus can lead to high blood pressure, which increases the risk of heart disease.
ii. Obesity:
It is associated with high blood pressure and heart disease. It is often the result of eating too much animal fat, and the heart has to work harder to move the body’s excess weight. Obesity may also lead to diabetes, stress on joints, and social rejection.
B. Starvation:
Starvation results in very restricted growth and development, particularly of muscles, leading to weakness. Resistance to disease is severely reduced, and death eventually follows. Starvation is often the result of famine, a lack of adequate amounts of food to support the population.
Famine may result from one or many of the following:
i. Poverty
ii. Overpopulation
iii. Drought
iv. Flooding
v. Crop failure due to disease
vi. Poor farming techniques
vii. War/political instability.
The world produces enough food to sustain the current population. However, some areas overproduce, while others do not produce enough. The cost of transporting the food to where it is required is often too high for those who need it.
Overpopulation may be controlled through education and the availability of birth control methods.
Poor farming techniques often worsen the effects of natural events, like drought and flood. Education on improved farming practices, and an understanding of the effects of deforestation and land clearing, may ease these problems.
Biological research is developing disease-resistant crops, and improved methods of disease control.
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3. The Human Alimentary Canal:
Human (heterotrophic) nutrition involves four basic stages:
1. Ingestion:
Taking food into the digestive system – ‘eating’.
2. Digestion:
(i) Mechanical:
Chopping and grinding food with teeth and muscular churning of the food, as in the stomach
(ii) Chemical:
Breaking large insoluble molecules into small, soluble ones (using enzymes).
3. Absorption:
Taking digested food into the bloodstream.
4. Assimilation:
Using the absorbed food in metabolic processes. Any food which cannot be digested or absorbed is passed out of the alimentary canal during egestion.
The main regions of the human alimentary canal are shown in Fig. 28.
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4. The Functions of the Main Regions of the Alimentary Canal:
A. Mouth:
This is the opening through which food is ingested into the buccal cavity (or mouth cavity).
The buccal cavity processes the food as follows:
1. Teeth mechanically digest the food (fig. 30).
2. Salivary glands secrete a solution (saliva) of the enzyme amylase to digest starch, and the protein mucin. Mucin is sticky, so it binds the food together and lubricates it.
3. The tongue rolls the food into balls or boli (singular: ‘bolus’) and pushes them to the back of the buccal (mouth) cavity for swallowing.
B. Oesophagus:
The oesophagus is a muscular tube connecting the mouth cavity and the stomach. Waves of muscle contractions, called peristalsis, travel down the oesophagus, steadily pushing each bolus towards the stomach.
C. Stomach:
The stomach is a muscular bag which churns the food for up to four hours.
The stomach wall secretes gastric juice which contains:
(i) The enzyme protease for starting the digestion of proteins, changing them to polypeptides.
(ii) Hydrochloric acid to:
a. Provide the correct pH for protease to work
b. Kill potentially harmful bacteria in food.
(iii) The enzyme rennin to clot protein in milk (in children only).
After treatment in the stomach, the food is in the form of soup-like ‘chyme’. It passes through a ring of muscle called the pylorus or pyloric sphincter, which relaxes to allow the food to enter the duodenum.
D. Duodenum:
The duodenum is a tube about 30 cm long which:
(i) Receives bile via the bile duct, from the liver.
(ii) Receives pancreatic juice from the pancreas, through the pancreatic duct.
(iii) Releases a digestive juice from its walls. This intestinal juice contains protease and the enzyme lipase, for fat digestion.
E. Pancreas:
The pancreas lies between the stomach and the duodenum. It secretes pancreatic juice, which it passes to the duodenum to help in digestion.
Pancreatic juice contains the following enzymes:
(i) Amylase for digesting starch
(ii) Protease for digesting protein
(iii) Lipase for digesting fat.
The amylase from the pancreas completes the job started by the amylase in the buccal cavity, changing any remaining starch to maltose sugar.
The protease changes any remaining proteins to polypeptides. Unlike the acid stomach contents, where protease starts the digestion of protein, the contents of the duodenum are very slightly alkaline. The alkaline bile from the liver neutralises the stomach’s hydrochloric acid.
Bile breaks up, or ’emulsifies’, fats into small droplets, which greatly increases their surface area. Lipase can then work on them far more quickly, changing fats into fatty acids and glycerol.
F. Liver:
The liver is the largest internal organ and is called the ‘chemical factory’ of the body. Like the pancreas, it is not technically part of the alimentary canal, but its function of producing bile is closely associated with digestion. Bile is a greenish-coloured fluid. It is alkaline due to the salts it contains, and is stored in the gall bladder before it is passed into the duodenum.
Its functions are:
(i) To neutralise acidic chyme from the stomach
(ii) To emulsify fat.
Large food molecules are almost ready for absorption. But first, enzymes in the intestinal juice change maltose into glucose by the enzyme maltase, and polypeptides into amino acids.
G. Ileum:
The ileum is the region where the absorption of digested food takes place.
To increase its efficiency, its surface area is increased in the following ways:
(i) It is about seven metres long (in a person)
(ii) Its walls are folded (‘pleated’) longitudinally
(iii) Its walls have millions of microscopic finger-like projections called villi (Fig. 32).
H. Colon:
The colon absorbs water, salts and vitamins. For more effective absorption, its walls are folded (transversely, or cross-ways, this time) to increase its surface area. Infections of the colon lead to diarrhoea.
Food is moved steadily along the duodenum, ileum and colon by peristalsis (which also occurs in the oesophagus). The indigestible fibre forms the bulk against which the muscles of the intestines can push.
I. Rectum:
The rectum is a muscular storage chamber where the undigested food (faeces) is held and moulded before being pushed out through the anus during egestion.
J. Anus:
The anus is the exit to the alimentary canal. It is closed by a ring of muscle (the anal sphincter) which is relaxed during egestion (or ‘defaecation’).
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5. Summary and Need of Chemical Digestion in the Alimentary Canal:
The Need for Chemical Digestion:
Most foods contain insoluble starch, protein and fat. These large, insoluble molecules cannot be absorbed into the blood stream, so they need to be broken down into small, soluble and absorbable (diffusible) ones. Glucose, amino acids, fatty acids and glycerol are the smallest forms of their ‘parent’ molecules.
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6. Teeth and the Part they Play in Mechanical Digestion:
A person has two sets of teeth in their lifetime. The first set (called milk teeth) last for around 10-12 years, then they are pushed out by the permanent teeth. There is only one permanent set of molar teeth – there are no ‘milk molars’.
In the permanent set, there are four types of tooth. The number of each type of tooth, given below, is expressed as ‘per quarter-jaw’. A quarter-jaw is one half of the top jaw, or one half of the bottom jaw.
a. Incisors:
There are two incisors in the front of each quarter-jaw. They are sharp, spade-like teeth for biting and cutting food. They are single-rooted.
b. Canines:
There is one canine per quarter-jaw. They are shaped like a cone, are sharp and used for biting and cutting food. They are single-rooted.
c. Pre-Molars:
There are two pre-molars per quarter-jaw. The surface of each tooth has two projections (‘cusps’) which are used for crushing and grinding food. They are double-rooted teeth.
d. Molars:
There are three molars per quarter-jaw. The tooth surface is square with four cusps, or points, for crushing and grinding food. They are double-rooted teeth. The third molars – wisdom teeth – do not usually appear until a person is at least 17 years old.
Therefore, the function of teeth in mechanical digestion is to bite, cut, crush and grind food (also loosely called ‘chewing’).
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7. The Importance of Proper Tooth Care:
If teeth are not properly cared for, they may suffer from dental caries (or dental decay).
Decay Process:
1. Food (particularly food containing sugar) becomes stuck between the teeth.
2. Bacteria settle in the sugary deposits, using them for their own metabolism.
3. The bacteria excrete acids which dissolve the outer non-living covering (enamel) of the tooth.
4. A cavity develops, in which more sugary deposits collect. More bacteria settle, excreting more acids. The size of the cavity increases.
5. Eventually, the decay reaches the living parts of the tooth. The first area affected is the dentine, where there are nerve endings. The tooth begins to ache. Then the decay reaches the pulp cavity – leading to an abscess (a painful swelling filled with pus).
Tartar:
If you do not clean your teeth, a mixture of food, saliva, cheek cells and bacteria collects at the neck of the tooth (where it enters the gum). This deposit is called tartar. The acids released by the bacteria damage the enamel of the tooth in that region, and cause gum disease.
Plaque:
If not removed, tartar hardens to form plaque. Plaque forms a solid barrier, so bacteria trapped between it and the tooth can decay the tooth without interference.
How to Care for Teeth:
(i) Do not eat sweet or starchy foods before going to bed. Saliva flow stops when we are asleep and prevents the sugar from being washed away. It is better to eat a raw, crunchy food, such as a carrot.
(ii) Brush teeth last thing at night, and first thing in the morning. Careful brushing removes plaque.
(iii) Use dental floss regularly to remove fragments of food from between the teeth.
(iv) Use a toothpaste which:
a. Contains fluoride to strengthen the tooth enamel
b. Contains a bactericide (to kill bacteria)
c. Is alkaline, to neutralise acids released by the bacteria.
(v) Visit the dentist regularly for an examination, and have treatment if required.
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8. The Absorption and Assimilation of Food:
Villi:
The villi of the ileum are specially adapted for the process of food absorption. They:
(i) Are extremely numerous – increasing the internal surface area of the ileum
(ii) Are very thin-walled (one cell thick)
(iii) Contain blood capillaries just beneath their walls
(iv) Contain special structures (lacteals) for absorbing fatty acids and glycerol
(v) Are able to move to bring themselves into close contact with food.
Amino acids and glucose, after absorption by the blood capillaries in the villi, are carried directly to the liver for the first stage of their treatment in the body. They are carried by a blood vessel called the hepatic portal vein.
Fats, after entering the lacteals in the villi, travel in the lymphatic system. They by-pass the liver and enter the circulatory system at a vein in the neck.
Assimilation:
The main food substances, absorbed as small soluble molecules, must now be built up into the larger molecules needed by the body.
Glucose (and any other simple sugars which can be absorbed by the villi) may be used as it is, as a substrate for respiration to release energy. However, after a meal, there is more glucose available than is needed immediately. It needs to be stored. For this purpose, it is built up into a large insoluble molecule called glycogen (similar to starch). It is stored in the cells of the liver and muscles. The uptake of glucose and its conversion to glycogen is controlled by the hormone insulin, secreted by the pancreas.
Amino acids are used in cells for building up proteins as the cells grow, and also for making special proteins such as enzymes. Amino acids and proteins are never stored. Any excess amino acids are broken down in the liver by a process called deamination.
Two separate molecules are produced as a result of deamination:
(i) A carbohydrate which can be changed to glycogen and stored.
(ii) Urea, a nitrogenous waste product (i.e. one which contains nitrogen), which passes in the blood from the liver to the kidneys for excretion in urine.
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9. The Role of the Liver in Glucose and Amino Acid Metabolism:
The liver is involved in the regulation of blood glucose levels. It is involved in changing glucose to glycogen, and storing glycogen when blood glucose levels are high. It also re-converts glycogen to glucose, and releases the glucose into the blood when blood glucose levels are low. The liver also removes excess amino acids from the blood by deamination.
Another major function of the liver is detoxification, the removal and breakdown of poisons (toxins) from the blood. One of these toxins is alcohol. Although the liver is able to remove small quantities of alcohol, even on a regular basis, frequent high levels of alcohol in the blood can eventually lead to liver disease (‘cirrhosis’).
Fat Metabolism:
The liver does not play a major part in fat metabolism. Once in the blood, fatty acids and glycerol re-combine to form tiny fat droplets. Fats at body temperature are in liquid form, so the word lipid is used to cover both fats and oils.
Lipids are stored in special storage cells in the skin (‘adipose’ tissue), and around the kidneys. Fat is a good insulator, or protector, against physical damage and low temperature, and is a very efficient energy store. But fat is also heavy, and can lead to obesity.