Classification, Functions, and Formation Plants and Animals Carbohydrates and Proteins
Many elements in varying combinations make up feed nutrients. These elements include carbon, hydrogen, oxygen, phosphorus, potassium, iodine, nitrogen, sulphur, calcium, iron, cobalt, chlorine, magnesium, sodium, copper, Florine, manganese, zinc, molybdenum, selenium and chromium.
Animal feed can be classified based on the nutrients they supply. There are six components of feed/food that are useful to the body;
- Carbohydrate
- Proteins
- Fats
- Minerals
- Vitamins
- Water
Carbohydrates are an essential compound of all organic life on this planet. Carbohydrates are sources of calories or energy which accounts for a large portion of an animal‘s daily food supply.
Carbohydrates comprises of Carbon, Hydrogen and Oxygen with an empirical formula Cn(H2O)n. This class of food includes sugars, starch and cellulose.
Formation of Carbohydrates in Plants
Carbohydrates are formed in plants during photosynthesis. This is achieved by reaction of carbon dioxide and water in the presence of sunlight.
Glucose (simple sugar) is formed from this process. Carbohydrates form 75 percent of all dry matter in plants.
Carbohydrates in Animals
Animals receive these starches through foods, especially those made from plant life such as grains and bread. Animals contain less than one percent carbohydrates, it is present in the liver, muscle and blood.
The carbohydrates present in animal body is also known as animal starch or glycogen. If they are not used immediately, they will be stored as fat. Based on digestibility and solubility carbohydrates can be divided into two groups.
Soluble carbohydrates, these are also called nitrogen free extract (NFE) which are made up of simple sugars, starch and hemicellulose. These group of carbohydrates are easily digestible in the body.
Insoluble carbohydrates include hard fibrous substances like crude fiber, cellulose and lignin. These group of carbohydrates are less digestible by non-ruminants and easily digested by ruminants through rumen microflora and micro fauna.
Carbohydrates Metabolism in Animals
The intermediary metabolisms of carbohydrate in the mammalian organisms are as follows:
Glycolysis – the breakdown of glucose or glycogen to pyruvate and lactate by the Embden – Meyerhof pathway.
Glycogenesis– The synthesis of glycogen from glucose.
Glycogenolysis– the breakdown of glycogen to glucose in liver and to pyruvate and lactate are main products in muscle.
Oxidation of pyruvate to Acetyl – COA – this is a necessary step prior to the entrance of the products of glycolysis into the citric acid cycle, which is the final common pathway for the oxidation of carbohydrate, fat and protein.
Gluconeogenesis – formation of glucose or glycogen from non-carbohydrate sources mainly in the citric acid cycle and glycolysis. Substrate for gluconeogenesis are glucogenic amino acids, lactate, glycerol and in the ruminant, propionate.
Hexose Monophosphate Shunt (pentose phosphate pathway) – is an alternative pathway to the Embden-Meyerhof pathway for the oxidation of glucose.
Functions of Carbohydrates
Carbohydrates serve as a major source of energy supply in animal body. They are essential component of production, temperature control and proper functioning of different parts of the body
Essential component of milk (lactose) which is important in lactation.
Carbohydrates are stored as glycogen, excess carbohydrates are converted to fat and stored in fat depot. These are reserved energy materials of the liver and muscle in animals.
Help in metabolism of amino acids and fatty acids.
Helpful in absorption of calcium and phosphorus.
Help in secretion of digestive juice in the gastrointestinal tract.
Provide suitable environment for rumen bacteria and protozoa.
Help in peristaltic movement of food 10.Maintain blood glucose level.
They are component of several important biochemical compounds such as nucleic acid, coenzyme and blood group substance.
Classification of Carbohydrates
1. Monosaccharide
Is a carbohydrate that cannot be hydrolyzed to simpler compounds. These are simple sugars with only one molecule of sugar.
They are soluble in water and sweet for example glucose, fructose, galactose.
2. Disaccharide
Is a carbohydrate that can be hydrolysed to two monosaccharide molecules for example sucrose, lactose, maltose.
3. Polysaccharide
Is a carbohydrate that can be hydrolysed to many monosaccharide molecules for example starch, glygogen, cellulose and fiber.
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There are also sweet carbohydrates, which are found contained in large quantities in many foods such as confectioneries, soft drinks, cakes, supplies only energy.
Others are fructose in fruit, honey, lactose in milk and malt.
Non-sweet carbohydrates – not sweet starch, are found it is the bulk in yams, bread, beans and cereals. These contain other valuable nutrients.
The main types of food/feed carbohydrates, their monosaccharide composition and their most common sources are listed below:
Table displaying the common food carbohydrates, types, composition and sources
| Type | Composition | Sources |
| Polysaccharides | ||
| Starch, dextrins | D-glucose | Cereals, roots, tubers, plantains |
| Cellulose | D-glucose | Cereals, fruits, vegetables |
| Glycogen | D-glucose | Liver, animal tissue, sweet corn |
| Hemicelluoses | L-Arabinose D-xylose | Cereals, fruits, vegetables |
| Gums | L-Rhamnose, D-galactose, mannose, glucose, glucuronic | Cereals, legumes, nuts, seaweeds |
| Pentosan | L-Arabinose, D-xylose | Fruits, vegetables |
| Oligosaccharides | ||
| Raffinose, Stachyose | D-gal, D-glu | Legume seeds, cereals |
| Dissacharides | ||
| Sucrose | D-glu, D-fru | Sugarcane fruits, vegetables |
| Maltose | D-glu | Starch syrups, malt, honey |
| Lactose | D-gal, D-glu | Milk, dairy products |
Examples of Carbohydrates include Yam, maize, sorghum, wheat, breadfruit, cassava, sugar, plants, cereals, roots and tubers, etc.
Proteins
Proteins are highly complex nitrogenous organic compounds occurring naturally in all living matter and forming an essential part of animal feed requirements.
Protein is important in feeding farm animals and human beings, because it is the nutrient found in highest concentration (after water) in organic and muscle tissues.
Protein is one of the critical nutrients particularly for young rapidly growing animals and for high producing mature animals such as dairy cows and fish.
The young, growing animal has the highest requirements for protein when expressed as a percentage of the diet.
In addition, productive functions such as gestation and lactation greatly increase the protein requirement because of the needs of the foetus during gestation and for milk protein production during lactation.
Optimal use of protein is a must in any practical feeding system, since protein supplements are much more expensive than energy, fibrous and fat feedstuffs and wasteful usage increase the cost of production in almost all instances.
If there is shortage of fat in the diet, then carbohydrates and proteins can be converted into body fat.
If there is shortage of carbohydrate in the diets, fats and proteins can be converted into energy, but if we are short of protein in the diet, carbohydrates and fats cannot be used to build up the body or repair the wear and tear that takes place.
It is therefore essential that an adequate quantity and quality of protein is supplied by the feed.
Protein Quality
Proteins are made up of some building blocks (individual organic compounds) called amino acids. Protein quality is a measure of the ability of protein supplement/feedstuffs to supply needed amino acids in the diet when ingested (plant and animal origins).
For practical purposes, protein quality refers to the amount and ratio of essential amino acids in a protein source.
The amino acids contained may either be essential amino acids (indispensable) which are those amino acids that are required for the functioning of the body but cannot be synthesized in the body hence, they must be supplied in the diet.
The non-essential amino acids are those amino acids that are necessary for the functioning of the body but can be synthesized within the body (dispensable). Therefore, a good quality protein is that which contains a high proportion of the essential amino acids.
The term biological value is used to express protein quality and it is dependent on the relative quantities of the essential amino acids present.
For all practical purposes, egg has a biological value of 100 and considered a standard good quality protein, however, cereals like maize/corn have low biological value of 40 as it lacks the amino acid lysine.
Ten (10) essential amino acids are Arginine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine. The non-essential amino acids are – Alanine, Asparagine, Aspartic acid, Glutamic acid, Glutamine, Glycine, Proline, Cysteine, Tyrosine, Serine.
It is the specific sequence of amino acids and the manner in which the amino acids strands are connected to each other than determines the physical and chemical properties of each individual protein and its biological functions.
Types of Protein Based On Origin
There are two main types of proteins; Animal Proteins and Plant Proteins.
Characteristics of Animal Proteins
These are proteins of animal origin.
Have better quality protein than vegetable proteins.
Have high biological value meaning high profile of essential amino acids.
They are called ―complete‖ protein.
They are costly (high price),
Not affected by seasonal variations and available all year round.
Lack or have limited anti-nutritional factors.
Require little or no processing before incorporation in animal feed.
Included in small quantities in animal feeds.
Chemical composition is relatively standardized.
Crude protein in most case is greater than 65% CP.
Examples include fish meal, meat meal, blood meal, egg, milk or dairy products, feather meal, chicken offal meal, maggot meal, termite meal, grasshopper meal, frog/toad meal.
Characteristics of Plant Proteins
These are proteins of plant origin,
They are often termed ―incomplete proteins.
Have low biological value (BV) lower profile of essential amino acids.
They are included in higher percentages in animal feed,
The percentage constituent crude protein is between 20-45% CP.
Its use is affected by seasonal availability, not available all year round.
It contains high levels of anti-nutritional factors especially in the raw state,
Proximate composition or chemical composition is not standardized i.e. variable.
Their price is low when compared to animal proteins.
They require a lot of processing before incorporation in animal feed.
They are deficient in one or more essential amino acids
Their protein quality is lower when compared to animal proteins
Examples include – soybean meal, groundnut cake, cottonseed cake, sunflower cake, palm kernel cake, rapeseed meal, jack bean, pigeon pea meal, castor seed meal.
Functions of Proteins
Proteins are complex polymer of amino acids, found in all cells, involved in most of the vital chemical reactions of plant and animals‘ metabolism.
Proteins are the chief structural units of protoplasm, cytoplasm and cell membrane.
Proteins in diets serve as primary source of amino acids the building block of cellular proteins.
The biological catalysts known as enzymes are proteins.
Some of the hormones, the regulators of chemical reactions are proteins or peptides.
Antibodies are complex proteins and are used for protection of the body.
Protein play an important role in the transport of water, inorganic ions, organic compounds and oxygen.
They can contribute through functional properties of proteins, in foods by contributing to colour, flavor, odour, foam formation e.g. maillard and browning reactions.
May also be used to provide energy e.g. meat, insects, soyabean meal, eggs, fish meal, groundnut cake, cowpea, milk.
Needed for growth, tissue maintenance and repair of worn out tissues, e.g. legumes such as soya bean, cotton seed, groundnut cakes, etc.
Make up a greater part of some body tissues such as brain, spinal cord, nerves.
Parts of animal body such as skin, hooves, wool, feathers and skin.
Note that for ruminants, lack of protein or a specific amino acid deficiency is not apparent as in non-ruminants.
This is because of the action of rumen microbes which can partially degrade a nitrogen source in the rumen to ammonia and most likely for some of the essential amino acids such as methionine or for some peptides.
However, high producing ruminant animals also by-pass some ingested proteins into the intestine without it being broken down in the rumen. Hence, it is probable that protein quality is more important under these circumstances than for animal producing at low levels and consuming much less feed.
In summary, many elements in varying combinations make up feed nutrients. There are six components of feed/food called nutrients that are useful to the body. These ingredients must be fed to the animal in their correct proportions.
Carbohydrates and protein are indispensable in animal production. They serve various function in the animal body. They are necessary for profitable animal production.
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