Intermediate Animal Nutrition

Introduction

In human nutrition, the food pyramid or “my plate” initiative encourages us to think about balancing the food groups that we consume. But have you ever considered the balance of nutrients required by the animals that you raise? Animals also require a balanced diet that consists of six nutrient classes: water, carbohydrates, lipids, protein, vitamins, and minerals. Each nutrient class meets unique requirements for the animals’ survival, growth, reproduction, and health.

 
Nutrients can be classified into one of six categories or classes.
 

Nutrient classes differ from feedstuff classes. While feedstuff classes (such as silages, roughages, concentrates, and additives) are used to identify ingredient types on feed tags, nutrient classes describe how feeds fit into the nutrient requirements for the animal. The most important requirements of animals are the supply of Energy and Protein.

There are various sources of nutrition. In the case of animals, roughage and concentrates are the main sources of nutrition. Roughages, exemplified by grasses, roughages and silages are rich in fibre and low in energy. On the other hand, concentrates such as grains are rich in energy and low in fibre.

The feed ingredients as applied to a bag of dog food.

	Nutrient	Dry Matter (%)
	Protein	24.5
	Fat	15.8
	Carbohydrate (NFE)	52.8
	Crude Fibre	1.8
Minerals	Calcium	0.78
	Phosphorus	0.7
	Sodium	0.30
	Potassium	0.75
	Magnesium	0.096
Vitamins	Taurine	0.13
	Vitamin C	291 mg/kg
	Vitamin E	785 IU/kg
(Taurine is added to this feed, an important vitamin for cats and dogs).

 

Water

 
Drinking water for livestock.

 

The “most essential” nutrient or, more likely, the “forgotten nutrient” is often referred to as water. Water is essential for many bodily functions, such as joint lubrication, growth, reproduction, lactation, digestion, metabolism, excretion, hydrolysis of nutrients, body temperature regulation, and transport of nutrients and waste. Depending on their size, diet, living situation, and physiological requirements, animals drink varying amounts of water. For instance, an animal that is pregnant or nursing will need more water than a dry animal. This is because an animal that is lactating continuously produces milk, which contains 85% water. Animals that graze on veld with a high-water content won’t need as much extra water as those fed a diet with only 10% moisture to supplement their diet. Animals kept in summer climates with efficient cooling, on the other hand, will use less water than those kept in hotter, more strenuous conditions.

Water is an essential nutrient needed by both people and animals. Access to clean, fresh water is becoming more and more difficult due to problems with water quality and quantity. When evaluating water as a nutrient, the amount consumed is typically the most important factor.

According to physiological and environmental factors, such as the animal’s type and size, they will require less water to consume feed that contains a lot of water, such as juicy grass. There is a huge range in water consumption. They require more if they are active, and they require significantly more if they are lactating. The need for water will also depend on the weather, which will be affected by heat, humidity, and wind. Except for camels, who only need water every 5 – 8 days, water should always be accessible, clean, and fresh.

 
(A) Sheep offered water from buckets cleaned daily, twice a week, or weekly preferred to consume water from the buckets cleaned most frequently. (B) After a week without cleaning, all buckets were cleaned yet the sheep refused to drink from the buckets that were previously dirty.

 

Keep in mind that young animals also require water Even when they are fed milk, it does not always satisfy their thirst, especially if they are active and the weather is warm, hot, dry, or even windy.

Water consumption (litre per day) of livestock species.

Livestock Species	Water consumption (l/day)
Camels	Every 5 – 8 days as much as they can drink (up to 100 l or one-third of body weight) or daily about 15 – 30 l.
Beef cattle	35 – 60 l per head.
Dairy cattle	30 – 80 l per head.
Horses	24 – 36 l per head.
Donkeys or Mules	Twice a day as much as they can drink (10 – 25 l).
Sheep and Goats	5 – 20 l per head.
Pigs	When ambient temperature increases from 10 – 25 °C, finisher pigs increase water consumption from 2.2 l to 4.2 l per day (l/day); therefore, the water systems and drinkers must be able to meet this demand. For grower and finisher pigs, water requirements can be 2.3 l for every kilogram of feed consumed
Chickens	A mature chicken will drink approximately 0.5 l of water each day in temperate weather, even as much as 1 full litre in warmer weather. Broilers will visit the chicken waterer much more often than this, due to their fast growth rate.

 
Nipple drinkers for pigs and chickens.
 

A. Importance of Water for Livestock

Animal nutrition is one of the most important factors in farming livestock. The level of nutrition on which animals are held will determine whether they can reach their genetic potential. One of the factors that will most impact the intake of feed, is the amount of good quality clean water that the animal has access to. It is essential for the survival, growth, and reproduction of all animals.

All animals need water as an essential nutrient to survive. It accounts for 60 – 70% of the live weight of an adult animal and 80% of the live weight of a newborn. Although an animal’s body can produce water through metabolic processes, the majority of the water it consumes comes from its feed and direct water trough drinking. Additionally, water is continuously lost through the lungs during breathing as well as through saliva, sweat, urine, and faeces.

• Water is needed by the animal to keep its body at a relatively stable temperature. It keeps the body cool through the production and evaporation of sweat.
• Water is necessary for digestion and absorption of feed, and aids in the hydrolysis of nutrients like carbohydrates, fats, and proteins.
• Water maintains the proper ion balance in body tissues as it is a neutral solvent, and readily encourages the ionisation of most substances.
• Water helps to transport products like metabolites, hormones, and gases throughout the body.
• Water aids in the elimination of waste products, through urine and faeces.
• Water also acts as a lubricant and support for joints and organs.

The amount of water an animal requires depends on its

• Physiological stage.
• Activity.
• Age.
• Rate of growth.
• Rate of respiration.
• Environment.
• Feed type.
• Feed intake.

 

B. How to Ensure Water Intake

Five properties need to be considered when assessing the quality of drinking water, including:

• Taste and odour (organoleptic properties).
• Presence of heavy metals, minerals, hydrocarbons, and so on.
• Presence of bacteria.
• Hardness, pH, and total dissolved solids of the water (physiochemical properties).
• The presence of excess minerals and compounds like nitrates, sulphates and iron.

Ensure that water is free from contaminants like toxins, heavy metals, mineral salts, and agricultural waste, among others. It should be noted that if the animal’s feed or water contains a large amount of salt, the animal may try to compensate by consuming excess amounts of water to get rid of the excess minerals.

Drinking water should be free from microbial contamination. Bacteria and other microbes can be toxic to livestock, and the consumption thereof may lead to problems like infertility and reproductive issues, diseases like foot rot, and decreased milk production. For this reason, drinking water should not be left to stagnate. Ensure that the water is readily available and at an acceptable temperature. Livestock are more likely to drink water that is cooler and under shade than water that is not.

Bacteria such as Shigella, Escherichia coli, Vibrio, and Salmonella, as well as viruses such as the Norwalk virus and rotaviruses, are among the many infectious microorganisms found in the water environment.

Water may contain protozoans such as Entamoeba, Giardia, and Cryptosporidium.

 

Carbohydrates 

 
Characteristics of corn in animal feeds.
 

Carbohydrates are the main source of energy for the regular functioning of the body.

The main source of carbohydrates in livestock feed are grains such as oats, wheat, barley, corn, sorghum, forages, and hay. Fats are an important part of the animal diet; nevertheless, they are needed in small amounts.

 
Sources of carbohydrates.
 

The liver cells of the majority of animals store carbohydrates as glycogen. However, plants are a very abundant source of carbohydrates. Starch, which is a form of carbohydrate, is most frequently found in the seeds of plants. The stems of some plants, including the sweet maize plant, sugar beetroot, and sugar cane, contain significant amounts of sugar.

Carbohydrates are carbon hydrates because their carbon, hydrogen, and oxygen ratios are the same as water, namely CH₂O. Carbohydrates are the primary source of energy in animal cells. The animal’s primary source of energy is dietary carbohydrates derived from plant-based products. The chlorophyll in plant cells absorbs solar energy, converts carbon dioxide and water into carbohydrates, and releases oxygen, according to the equation below. The liver and kidneys can turn glycerol into glucose, which fuels cellular metabolism.

  

Carbohydrates may be found in the plant cell as sugar or starch, or they may be linked to the cell wall structure (such as cellulose) in the plant cell. Animal cells use metabolic processes to release energy from the feed’s carbohydrates when they consume plant materials such as cereal grains, grass, and fodder.

In general, animal metabolism generates energy through a process that is the opposite of photosynthesis in plants.

The energy content of cellulose and hemicellulose is locked up, resistant to digestion, and only usable by animals that use microbes to aid in digestion. Short-chain fatty acids (acetate, propionate, and butyrate) are produced during fermentation in the rumen of ruminants, the caecum, and colon of horses, and the stomach and intestines of rabbits. These finished goods are also a byproduct of the fermentation of sugars and polysaccharides.

 
Ruminant papillae absorb energy from microbes that ferment carbohydrates – both structural and non-structural to volatile fatty acids.
 

The sugars and starches also supply energy to the farm animal (Less than 5% of the metabolizable energy is derived from these sources). As mentioned above, sugars and starches are also broken down in the rumen by microbial fermentation and volatile fatty acids (Volatile fatty acids are the main energy source for ruminants, providing approximately 70% of the total energy requirements. They are used primarily by the microorganisms for reproduction and growth, with the excess production being used by the ruminant itself ) are formed.

Since the microbes are responsible for digestion in the rumen, it should be remembered that it is the micro-organisms that are being fed rather than the animal. This is often forgotten in the feeding management of ruminants. When changes in the feed occur, the microbial population in the rumen changes. Some micro-organisms increase in number if the feed source that they prefer is provided while others will decrease in number since their feed source is not being supplied. Because of this continuous adaptation of the microbial population to the feed provided, it should be remembered that new feeds should be introduced to ruminants over a week to two-week period. This allows the microbial population time to adapt to the new feed source. If sudden complete shifts are made in the diet, the microbial population will die.

Structure and Classification of Carbohydrates:

Monosaccharides are often referred to as simple sugars (e.g., glucose) and cannot be hydrolysed into simpler compounds. The monosaccharides are readily absorbed by simple diffusion in the small intestine The amylase enzymes are responsible for hydrolysing the more complex sugars to their simple free derivatives.

Monosaccharides are the simplest forms of carbohydrates.

Disaccharides are made up of two monosaccharides bonded together by a glycosidic (covalent) bond. The following are some of the common disaccharides:

• Table sugar (sucrose-glucose + fructose).
• Milk sugar (lactose-glucose + galactose).
• Malt sugar (maltose-α-D-glucose + β-D-glucose).
• Cellulose (cellobiose-β-D-glucose + β-D-glucose).

Thus, the disaccharide sucrose is converted to fructose and glucose, maltose is converted to glucose, and lactose is converted to galactose and glucose. Among the different disaccharides, lactose (milk sugar) is the only carbohydrate of animal origin. However, cellobiose as a component of cellulose is important in animal nutrition. Monogastric animals cannot digest cellulose because they do not produce the cellulase enzyme that can split β-D-glucose.

Polysaccharides as their name implies, are made by joining together large polymers of simple sugars. Polysaccharides are the most important carbohydrate in animal feed. Polysaccharides are composed of many single monosaccharide units linked together in long, complex chains. The functions of polysaccharides include energy storage in plant cells (e.g., seed starch in cereal grains) and animal cells (e.g., glycogen) or structural support (plant fibre).

Starch is the chief carbohydrate source in the diet of monogastric animals.

For tissue growth, egg production, and maintenance, chickens require glucose, whereas pigs require fructose. On days 14 and 21, sows fed a fructose-based diet produced significantly more milk. Although it does not affect an individual’s weight or milk production, fructose can increase the size of a primiparous sow’s litter.

 

Fats Or Lipids

Several sources of fat can be used in cattle diets, including commercially prepared fat additives like Megalac. Additional sources include fishmeal, whole oilseeds like soybeans and cottonseeds, and food byproducts like bakery waste.

 
Cotton seeds (left) and soya bean seeds (right).
 

Lard and tallow are examples of animal fats that are frequently used in pig feed, along with coconut oil, palm oil, palm oil mix, corn oil, rapeseed oil and soybean oil. Fish oil is an example of a marine fat source.

Tallow, lard, poultry fat, and other types of white grease are a few saturated fats that can be used in poultry diets. Unsaturated fats that are suitable for human consumption include canola, soy, and corn oils.

Tallow is the rendered fat of cattle and sheep predominantly, although other animals can be brought into the equation, such as horses, goats, and other dead stock. Pig fats have a different composition and are too soft to become tallow and form a group called greases. The edible form of pig fats becomes lard after rendering and cooking under pressure. The predominant source of tallow comes from cattle and is a by-product of the meat industry.

Fats are the primary storage form of energy (e.g., oil in seed) and serve as an animal’s body’s “saving account.” For example, the abdominal fat pads in chickens and back fat in pigs are mostly triglycerides.

Lipid Classifications:

1. Simple lipids:

Esters of fatty acid with an alcohol, e.g., 1 glycerol + 3 fatty acids (commonly called triglyceride or triacylglycerol.

Simple lipids like triglycerides are more common and are an important component in animal rations (e.g., vegetable oil and animal fats such as tallow or lard).

2. Compound lipids:
   • Glycolipid.
   • Lipoproteins.
   • Phospholipids.
   • Derived lipids.

Compound lipids are composed of lipids plus a nonlipid molecule (e.g., protein) Lipoproteins (lipid + protein) are examples of compound lipids and are used for lipid transport (like a courier). Within the animal body, compound lipids are more important in physiology and metabolism (e.g., lipid transport, and phospholipids as part of cell membranes).

Fat digestion begins in the duodenum (small intestine) when the triglycerides come into contact with pancreatic lipase and bile salts. Triglycerides (the dietary lipids) are emulsified to glycerol and monoglycerides, free fatty acids and diglycerides.

In the small intestine’s lumen, sodium ions, bile salts, and monoglycerides come together to form a micellar solution. The monoglycerides and fatty acids can enter the cells when the lipid micelles travel through the inter-microvillar spaces of the intestinal tract. The long-chain-free fatty acids and monoglycerides are re-esterified back into triglycerides once they have reached the intestinal mucosal cells. They are subsequently covered in a layer of lipoprotein, cholesterol, and phospholipid to create chylomicrons, which are then removed by the lymph system.

Short-chain fatty acids merely pass from the mucosal cells directly into the portal blood where they are transported to the liver as free fatty acids.

Why Add Fats to Animal Diets?

Nutritionally, fats are excellent sources of energy and are essential to the survival of animals. Fats are the sole source of essential fatty acids (those that cannot be made by the body) for animals. Fats can also provide fat-soluble vitamins. However, this role is very minimal in livestock as feeds are supplemented with vitamins.

 

The most important role of dietary fats is to provide essential fatty acids.

As the fat content of the diet increases, the energy density of the diet increases.

 

Physically, the addition of fats is associated with:

• The improvement of feed quality.
• The reduction of dust in feed.
• The reduction of feed particle separation during processing.
• An increase in palatability.
• An increase in digestive lubrication (i.e., emulsification and rate of passage).
• An increase in feed digestibility.

 

Protein

The Greek word “proteios” means first or most important, and the word “proteins” was first used by Dutch chemist G. J. Mulder. Proteins are organic substances made of various amino acid building blocks (basic units) connected by peptide bonds. A tripeptide has three amino acids and two peptide bonds, compared to a dipeptide’s one peptide bond and two amino acids. A polypeptide is a peptide that contains more than ten amino acids. Large polypeptides are essentially what proteins are. The order of the individual amino acids that make up a protein’s polypeptide chain is what first determines the structure of the protein.

Proteins are necessary for life because they are the main structural building blocks of animal tissues (including skin, muscles, wool, feathers, tendons, and eggs). Additionally, proteins are involved in biochemical (like enzymes), immunological (like immunoglobulins), transport-associated (like lipoproteins), and additional regulatory (like hormones) activities. Proteins can also provide energy when necessary.

Supplements with animal protein are more expensive and more difficult to find. Furthermore, there are top-notch plant-based protein supplements available. Some grains and plant seeds can produce oil, which results in a byproduct that is a good source of protein. These plant sources of protein are frequently more affordable and available than animal protein supplements. Examples include:

• Soya bean oil cake meal.
• Peanut oil cake meal.
• Sunflower oil cake meal.
• Canola oil cake meal.
• Other oilcake meals like cottonseed oil cake meal.

There are also other by-products with protein content higher than 10% but these have a lower-quality protein. These include the by-products of the milling companies such as wheat bran and pollard.

Ruminants do not require such premium protein feeds. For the ruminant microbes, such high-quality protein feeds are not required. The microbes in the rumen will digest the protein in the feed and incorporate it into the animals’ bodies. To ensure that high-quality protein feeds for ruminants pass undigested into the abomasum, where they will be broken down by enzymes and then absorbed as amino acids in the small intestine, you must protect those protein sources from rumen microbes. The protein in the feed will be broken down by the rumen and assimilated by the animals. Therefore, it is important to protect high-quality protein sources from rumen microbes when feeding ruminants. This will allow the protein sources to pass undigested into the abomasum, where they will be broken down by enzymes and then absorbed as amino acids in the small intestine.

Therefore, animals with monogastric (single stomach) digestion must eat feed rich in protein and energy. This is done to avoid cellulose, which a monogastric animal cannot digest. As a result, mono-gastric animals cannot utilise cellulose-rich feeds like lucerne and other roughages as effectively as ruminants can.

On the other hand, horses and rabbits use lower digestive tract fermentation, where the microbial activity takes place in the large intestine’s caecum. Due to these variations in digestion capacity, ruminants and monogastric animals have various feed requirements. Additionally, different animals have different nutrient needs (both quantity and quality) depending on:

• Their species.
• Their breed.
• Their age.
• Their sex.
• Their production potential.
• Their stage of production.
• Whether they are ill or healthy.
• The product they produce (whether wool, meat, milk, and so on).

Most of the products produced by farm animals contain high levels of proteins in their structure, for example, milk, fibre, and meat. These proteins are built up from certain amino acids in different combinations that will give the protein its specific characteristics.

 

A. Protein Quality and Amino Acids

Protein quality is a term used to describe how well a protein from feed matches animal requirements. With high-quality protein, less is needed in the diet. Put differently, protein quality refers to the availability of amino acids that the protein supplies and digestibility considers how the protein is best utilised.

Several factors can affect the protein quality, including:

• Amino acid profile.
• Content and balance of essential and non-essential amino acids.
• Content of limiting amino acids.
• Protein digestibility and bioavailability.

Instead of a requirement for protein, animals have an amino acid requirement. The main purpose of dietary protein is to supply enough of the essential amino acids. As a result, the amino acid profile of the diet, the amount of essential and limiting amino acids, as well as the digestibility and physiological use of amino acids after digestion, all affect the quality of feed protein. Non-ruminants need these components more than other animals. Additionally, ruminant animals need solubility and digestibility.

All peptides and polypeptides (a peptide with more than ten amino acids is referred to as a polypeptide) are composed of alpha-amino acid polymers. The twenty alpha-amino acids are connected to the structure of mammalian proteins. The body contains additional amino acids, both free and combined. These amino acids that aren’t connected to proteins perform particular functions. Several of the amino acids found in proteins have functions that are distinct from those involved in the synthesis of peptides and proteins.

 

Amino acids are the building blocks of proteins.

 

It is known that there are more than 300 different amino acids in nature. Animal proteins are made up of about 20 amino acids. Some of the 20 amino acids are essential (indispensable) amino acids, which are required for animal life and cannot be synthesised by animal tissues or cannot be synthesised in sufficient amounts to support metabolic processes. Citrulline and ornithine are two additional amino acids that are needed for cellular metabolism but are absent from animal tissues.

 

Essential amino acids must be supplied through the diet since animals cannot synthesise them or cannot make the adequate amount needed.

 

Ten essential amino acids are needed by pigs, dogs, and humans, while eleven essential amino acids are needed by chickens and cats. The essential amino acids that monogastric animals need are listed below.

List of essential amino acids and their common abbreviations:

1. Arginine (Arg).
2. Histidine (His).
3. Lysine (Lys).
4. Isoleucine (Ile).
5. Leucine (Leu).
6. Methionine (Met).
7. Phenylalanine (Phe).
8. Threonine (Thr).
9. Tryptophan (Try).
10. Valine (Val).

In addition to these 10 essential amino acids, cats and chickens need the following extra amino acids:

11. Cats need taurine (Tau).
12. Chickens need glycine (Gly).

Ruminants require the same amount of amino acids as humans, but they digest their food differently. In addition to their enzymes, ruminants also use microbial digestion. Rumen microbes can create specific amino acids from nitrogen sources other than proteins. This reduces the ruminant’s reliance on dietary sources of essential amino acids from outside.

These alpha amino acids are crucial protein building blocks even though the body can convert essential amino acids into non-essential amino acids. Pig, poultry, and other monogastric animal feeds are supplemented with those amino acids when it is found that a mixed feed is out of balance or lacking in certain essential amino acids. For the initial balancing, the person putting together a ration will use naturally occurring, protein-rich feed sources and supplements, and will only add pure amino acids in small quantities, which can play a significant role due to their high cost. This is done purely to keep the cost of the feed as low as possible. (This feed formulation is referred to as “least expensive”). Small amounts of the amino acids that are supplemented will be combined with tiny amounts of minerals and vitamins.

Different essential and non-essential amino acids.

Amino Acid	Essentiality
Arginine (Arg)	E
Histidine (His)	E
Lysine (Lys)	E
Aspartic acid (Asp)	NE
Glutamic acid (Glu)	NE
Alanine (Ala)	NE
Glycine (Gly)	E (chickens)
Isoleucine (Ilu)	E
Leucine (Leu)	E
Valine (Val)	E
Serine (Ser)	NE
Threonine (Thr)	E
Cysteine (Cys)	NE
Methionine (Met)	E
Phenylalanine (Phe)	E
Tryptophan (Try)	E
Tyrosine (Tyr)	NE
Hydroxyproline (Hydro)	NE
Proline (Pro)	NE

 

What are Protein Concentrates?

Protein concentrates are dietary supplements for people or animals that are made from vegetable or animal matter and have a high protein content. The most typical two are leaf protein concentrate (LPC) and fish protein concentrate (FPC). Whey protein concentrate is also widely used.

Young leaves are processed to create LPC by being ground into a paste, pressing the paste, and then centrifuging or filtering a liquid portion that contains protein. Compared to perennial grasses, herbaceous plants, and legumes like clover and lucerne produce more protein concentrate. All LPCs need supplements because they are deficient in lysine and methionine, two nutritionally essential amino acids, which are comparable to soybeans, the oilseed with the highest protein content.

As a rule, you can consider any protein feed of animal origins such as fishmeal, bone meal, and blood meal as protein supplements with high-quality protein. The presence of essential amino acids in them is good. Dry milk powder is also a protein supplement with good-quality protein. There are other by-products with a protein content higher than 10%. These include milling industry byproducts like pollard and wheaten bran.

 

B. Non-Protein Nitrogen (NPN)

Both actual protein and non-protein nitrogen (NPN) are present in crude protein. Proteins are not the only things that contain nitrogen. The rumen microbes can obtain nitrogen from a variety of NPN substances, and they combine this nitrogen with available carbon sources or energy to create microbial protein in the rumen. True protein is also known as “natural protein” in some circles. In the rumen, it either degrades or it doesn’t. Rumen Undegradable Protein (RUP), in contrast to Rumen Degradable Protein (RDP), is not degraded in the rumen but may be in the small intestine. It is also known as Rumen Bypass Protein and Undegradable Intake Protein (UIP).

 
The digestive route of Crude Protein in a typical ruminant.
 

Combining RDP and RUP results in crude protein. A minimum of RDP and NPN must be present in the animal’s diet for it to receive Microbial Crude Protein (MCP), which is a balanced protein in terms of the amino acid content that the animal needs. RUP and MCP are examples of metabolizable proteins (MP). The term “metabolizable protein” (MP) categorises protein requirements into needs for animals and rumen microorganisms. Metabolizable protein (MP) is the name given to the actual protein that is absorbed in the animal’s intestine.

 

Vitamins

Only a small amount of vitamins are needed for several physiological processes. Vitamins are a group of chemically unrelated organic molecules. The term “vitamin” refers to a collection of chemicals with specific metabolic roles and is derived from the term “vital amine.” Despite being organic substances, vitamins are not energy-producing like other macronutrients and cannot synthesise structural compounds. However, they support several metabolic processes as coenzymes or enzyme precursors.

The animal must consume the majority of its vitamins, but some can be made by the rumen and hindgut microbes or by being exposed to sunlight. Dietary vitamin deficiencies lead to disease conditions, decreased productivity, poorer animal welfare, and weakened immune systems in farm animals. Dietary requirements for vitamins are incredibly low. Mega-doses of some vitamins, such as vitamin E, have recently been added to animal diets to improve food quality and boost animal immunity.

Vitamins are classified into fat- and water-soluble vitamins.

 
Fat- and water-soluble vitamins required by animals.
 

Characteristics of fat- and water-soluble vitamins.

Fat-Soluble Vitamins	Water-Soluble Vitamins
Associated with fat during digestion and absorption. Storage in the liver, adipose tissue, and excess storage can be toxic for some vitamins (e.g., A and D). No daily need. Deficiency is very slow.	Soluble in water and excess excreted through urine. No storage and is less toxic. Daily requirement (except vitamin B12). Serve as a cofactor in biochemical reactions. Deficiency is fast.

 

Vitamin A

Masamichi Mori named this vitamin A when he discovered it in 1922 as a “fat-soluble factor” found in butter and fish oil. Retinol (alcohol), retinal (aldehyde), and retinoic acid are three closely related substances that collectively fall under the umbrella term “vitamin A.” Retinol is the only biologically active form of vitamin A.

The maintenance of epithelial cells, which line the surface of the body (such as the skin) and the mucous membranes of body cavities (such as the respiratory, urogenital, and digestive tracts), is one of the many functions of vitamin A in the body. Other functions include vision, bone growth, reproduction, and reproduction.

Vitamin D

A class of sterol compounds found in vitamin D control the body’s metabolism of calcium and phosphorus. A “sunshine” vitamin – vitamin D is created when sterols found in plants and animal skin are exposed to radiation. Ergocalciferol (vitamin D2, activated plant form) and cholecalciferol (vitamin D3, activated animal form) are the two main types of vitamin D.

Cholecalciferol (vitamin D3) is the form of vitamin D that is of nutritional value to most animals.

Ergocalciferol (vitamin D2) in plants is not produced by living plant cells; rather, it is created when sunlight is exposed to plants after harvest (or damage). Forages and hay that have been sun-cured are good sources of vitamin D for grazing ruminant animals. Animals kept in close quarters, such as those used in contemporary commercial pig and poultry operations, without access to sunlight, will need vitamin D.

Vitamin E

Vitamin E is a term that is used to describe a group of chemically related compounds called tocopherols and tocotrienols. Among the different isomers, α-tocopherol is the most active biological form of vitamin E and is the one that is added to animal diets. Other isomers with less biological effects include β-, γ-, δ-tocopherol and α-, β-, γ-, δ tocotrienols. Most commercially available vitamin E is DL-α-tocopheryl acetate. One IU of vitamin E is defined as 1 mg of all-rac-α-tocopherol acetate.

The function of vitamin E in the body is to serve as a biological chain-breaking antioxidant and to protect cells and tissues from oxidative damage induced by free radicals and other lipid oxidation products. Vitamin E prevents the oxidation of lipids by serving as a free radical scavenger and donates electrons from the hydroxyl group of the molecule.

In prepared feeds, the formation of such peroxidised compounds can cause a reduction in palatability, rancidity, and destruction of nutrients and can also affect animal health while reducing the organoleptic and sensory quality of the food produced. In addition to lipids and oxidative stress, vitamin E can protect other nutrients such as proteins and vitamin A. Due to these roles, the level of vitamin E in a diet depends on the level of polyunsaturated fatty acids, degree of peroxidative damage, and other external stressors.

Vitamin E is an antioxidant, and high levels of polyunsaturated fatty acids and vitamin A in the diet increase the requirement for vitamin E.

Vitamin K

Quinones are a group of substances that are present in vitamin K. Green plants contain vitamin K1 (phylloquinone), and bacteria in the hindgut produce vitamin K2 (menaquinones). In the GI tract, fat and vitamin K are both readily absorbed. The liver changes vitamins K1 and K3 into K2 before they can be utilised. The metabolically active form of vitamin K is called menaquinone. Menadione, a synthetic form of vitamin K3, is the vitamin K subunit most frequently found in animal diets. The production of prothrombin, a blood-clotting protein, requires vitamin K. Numerous proteins, including thromboplastin, prothrombin, fibrinogen, and fibrin, are required for the blood-clotting process.

Another antagonist of vitamin K is Warfarin, a rat poison causing anticoagulation. It is also a competitive inhibitor of vitamin K. Vitamin K is routinely administered in rodenticide poisoning in pets because the active ingredient (Warfarin) in these rodenticides is anticoagulant, causing bleeding and haemorrhaging.

 

Minerals

Minerals are inorganic substances that are necessary for the physiological and metabolic processes of an animal’s body. About 4% of an animal’s body weight is made up of mineral matter, which is necessary for the animal to remain alive and healthy. More than any other single class of nutrients, minerals are an essential component of all biological processes in the body. The activities and functionality of vitamins, osmotic balance, detoxification, immunity, cell membrane function, acid-base balance and regulation, and structural support and growth (i.e., bone) are among the functions. Gene expression and regulation of enzyme systems that regulate cellular function are also included. 21 minerals are listed as essential in scientific literature.

• Minerals are inorganic elements present in animal tissue.
• Minerals do not provide energy.
• Minerals are needed in minute quantities in the diet.

Minerals cannot be added to a diet in their elemental forms but rather need to be added as salts that are combined with other minerals (NaCl, CaCO₃, MnSO₄, and so on).

Minerals are classified into two groups—macro and micro (trace) minerals—based on the amounts needed in the diet and not based on their importance for physiological functions.

Essential macro and micro minerals as percentage or parts per million, respectively, of the diet.

Macro-Mineral	%	Micro-Minerals	ppm
Calcium (Ca)	1.55	Iron (Fe)	20 – 80
Phosphorus (P)	1	Zinc (Zn)	10 – 50
Potassium (K)	0.2	Copper (Cu)	1 – 5
Sodium (Na)	0.15	Manganese (Mn)	0.2 – 0.5
Chloride (Cl)	0.11	Iodine (I)	0.3 – 0.5
Sulphur (S)	0.15	Cobalt (Co)	0.02 – 0.1
Magnesium (Mg)	0.04	Molybdenum (Mo)	1 – 4
		Selenium (Se)	0.3 – 3

 

Macro-minerals are those minerals that are present in the animal body in significant amounts and are needed in high concentrations in the diet (> 0.01%). Calcium, phosphorus, magnesium, sulphur, and electrolytes (sodium, potassium, and chloride) are examples of macro-minerals. The structural components of an animal’s skeleton are composed of macro elements like calcium, phosphorus, and magnesium. Additionally, phosphorus plays a crucial part in the animal’s energy metabolism. A lack of copper causes symptoms ranging from anaemia to a reduction in fertility to the loss of crimp in wool. Copper is necessary for the functioning of many different enzymes. Cobalt is a component of Vitamin B12, which is necessary for the body to use propionic acid.

The functions of macro-minerals, including electrolytes, and diseases or conditions caused by deficiencies.

Macro-Mineral	Function	Deficiency
Calcium (Ca)	Structural (99%) – bones and teeth. Metabolic (1%) – muscle contraction and blood coagulation.	Rickets. Osteomalacia. Osteoporosis.
Phosphor (P)	Structural (80%) – bones and teeth. Metabolic (20%) – intracellular anion and ADP or ATP.	Rickets. Osteomalacia. Pica.
Magnesium (Mg)	Structural (50%) – bones and teeth. Metabolic – phosphate cofactor (ADP or ATP) and oxidative phosphorylation.	Grass tetany.
Sulphur (S)	Structural – skin, hair, feathers, collagen, and cartilage. Metabolic – regulatory functions.	Reduced wool growth. Reduced weight gain.
Sodium (Na)	Main extracellular cation. Maintains osmotic pressure, membrane potentials, and acid-base balance.	Animals become dehydrated. Uncoordinated moving ability. Shivering. In severe cases, animals could die of arrhythmia of the heart.
Chloride (Cl)	Main extracellular anion. Maintains osmotic pressure and acid-base balance.	Deficiency symptoms observed in lactating cows: Pica. Lethargy. Anorexia. Decreased milk production. Constipation. Cardiovascular depression.
Potassium (K)	Main intracellular cation. Maintains osmotic pressure, membrane potentials, and acid-base balances.	Muscle cramps. Constipation. An abnormal heart rhythm (arrhythmia) – skipped heartbeats or an irregular heartbeat.

 

Calcium and Phosphorus

Both calcium (Ca) and phosphorus (P) are structural components found in animal bodies. In bones and teeth, a substance called hydroxyapatite is where 99% of the calcium and 80% of the phosphorus in an animal’s body are found. The remaining 1% of calcium can be found in cellular fluids, where it takes part in several metabolic and physiological processes like blood coagulation, maintaining nerve impulse and cell permeability, activating specific enzymes, causing muscles to contract, and acting as ion channel activators.

Another crucial factor is the calcium-phosphorus ratio. Phosphorus and extra dietary calcium combine to form insoluble complexes that hinder P absorption. High dietary levels of P in the form of phytates can interfere with Ca absorption. The majority of the P in cereal grains is bound as phytate P (> 30 – 60%), which reduces the absorption of other nutrients by forming complexes that are resistant to the action of digestive enzymes.

It is advised to use Ca: P ratios of 1: 1 for small animals and 2: 1 for large animals. Feeding diets with an incorrect Ca: P ratio or supplementing feeds with excessive amounts of one of these minerals can result in a calcium-phosphorus imbalance These problems can lead to financial loss and affect animal welfare, productivity, and skeletal health.

Rickets in young animals and osteomalacia in older animals occur due to Ca and P deficiency.

Hypocalcaemia from a severe Ca deficiency can lead to tetany and convulsions. The classic manifestation of hypocalcaemia and Ca tetany in dairy cows are milk fever, also referred to as parturient paresis.

Due to the high Ca demand of lactation combined with hormonal insufficiency, milk fever in high-producing dairy cows always develops within the first 24 hours after calving. Typically, calcium minerals from bones are used to supplement the high demand for milk calcium. However, hormones, particularly parathyroid hormone (PTH), have an impact on the mobilisation of bone minerals. A good management strategy is to ‘prime’ or stimulate endocrine activity at least 14 days before calving so that when lactation starts, Ca mobilisation from bones increases as a result of increased PTH secretion. The animal’s electrolyte balance is crucial for preventing milk fever. Following intravenous Ca administration, milk fever-stricken cows typically recover quickly.

Providing a low Ca diet during the dry period in cows is recommended to minimise the incidence of milk fever in dairy cows.

Cage layer fatigue, which resembles milk fever in dairy cows, frequently develops in young, high-producing hens during the peak egg-producing phase (> 35 weeks of age). High Ca levels are required for the formation of eggshells during egg laying. Leg weakness results from increased bone mobilisation brought on by a Ca deficiency. Affected birds might be reluctant to move, move to a cage corner, or lay eggs with soft or deformed shells. Egg-laying hens need a minimum of 3.3 g of calcium per day to produce eggs, which is much less than other animals’ needs.

 

Magnesium

Magnesium is the third most common element in the body and is found in phosphates, carbonates, skeletal muscle, liver, and cell membranes.

• Mg is involved in providing structural roles.
• In the cells, Mg is required to activate several enzymes that split and transfer phosphatases as a cation in the intracellular fluid.
• Mg is involved in the metabolism of carbohydrates and proteins along with Ca, sodium, and potassium.
• Mg plays an important role in muscle contraction and transmission of nerve impulses.

Grass tetany is the most common Mg deficiency in grazing animals.

 

Sulphur

Sulphur serves as a structural component of skin, hair, wool, feather, cartilage, and connective tissue.

• Sulphur is required by the body mainly as a component of S-containing organic compounds. These include chondroitin sulphate; mucopolysaccharide, found in cartilages; the hormone insulin; and the anticoagulant heparin.
• Sulphur is also an integral part of three amino acids: methionine, cysteine, and cystine. The largest portion of S in the body is found within S-containing amino acids. A high-S-containing amino acid is generally recommended in the diets of birds during rapid feather growth as well as in the diets of sheep for wool growth.
• Sulphur is a component of two B vitamins (thiamine and biotin) involved in carbohydrate and lipid metabolism. As a component of coenzyme A, S is important in energy metabolism too.

 

Electrolytes (Sodium, Potassium, and Chlorine)

Electrolytes are dissolved, electrically charged materials that keep an animal’s electrical neutrality. Acid-base balance is determined by the difference between total intake and excretion of anions and cations. Because sodium, potassium, and chlorine are all electrolytes that support ionic balance and keep cells alive, they are discussed together in this section. Electrolytes are necessary to maintain osmotic pressure in intracellular and extracellular fluids, cell membrane signal transduction, and acid-base balance (blood and tissue pH).

Across species, normal electrolyte ratios are remarkably constant. The animal body has control mechanisms in place to maintain these mineral concentrations. They must, however, be consumed daily and cannot be stored.

Sodium (Na): The most prevalent extracellular cation present outside of cells and in the blood. Together with other ions, sodium helps to maintain cell permeability during the active transport of nutrients across membranes. The sodium pump, also known as the “Na pump,” controls electrolyte balance and makes a significant contribution to the body’s basal metabolic rate. Sodium is necessary for both nerve impulse transmission and muscle contraction.

Common salt (NaCl) is added to the diets of all animals, and grazing animals are given free access to it. Salt is also used to deliver other trace elements, such as iodised salt or trace-mineralised salt. The standard procedure calls for adding 0.3 – 0.5% salt to the diets of pigs and poultry.

Potassium (K): The most prevalent cation that is present in high concentrations within cells (intracellular fluid) is K. The osmotic force that maintains fluid volume is generated by ionised K inside the cells. Cellular potassium is involved in several enzymatic processes. For healthy heart muscle function, maintaining potassium balance is essential.

Chloride (Cl): The positively charged cations K and Na are balanced by the negatively charged anion Cl. Two-thirds of the anions in extracellular fluid that are involved in controlling osmotic pressure are Cl. The production of hydrochloric acid, which is necessary for the activation of gastric enzymes and the beginning of protein digestion in the stomach, also depends on chlorine. NaCl is the source of chloride in animal diets.

Electrolyte balance is important in maintaining skeletal health and growth in pigs and poultry.

In ruminant animals, electrolyte balance is essential for avoiding acidosis and alkalosis. Dietary cation-anion difference is frequently used in dairy cattle feeding to lower the incidence of milk fever. Prepartum alkalosis may increase milk fever in dairy cattle, whereas acidosis may prevent it. Prenatal diets are rich in forages and also contain high levels of K, which may impair the cow’s ability to keep her body’s calcium levels balanced and result in milk fever. Diets that lower blood pH can result in an increase in blood Ca, which lessens milk fever.

Alkaline diets increase the incidence of milk fever, and acidic diets prevent milk fever.

Micro-minerals are those minerals needed in trace amounts (less than 0.01%), milligrams, micrograms, or parts per million (ppm). Manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), selenium (Se), iodine (I), cobalt (Co), molybdenum (Mo), and chromium (Cr) are among the microminerals discussed.

 

Manganese

Animals require the trace mineral Mn in their diets. Mn is found throughout the animal body, but it is most abundant in the bone and liver. The organic matrix of the bone’s mucopolysaccharide needs manganese to be produced and maintained. Mn is thus crucial for healthy bone development. As a result, Mn-deficient animals have slow or abnormal bone growth but normal tendon growth. As a result, young ruminants develop crooked calves and chicks develop pyrosis (slipped tendon). Additionally, manganese is a crucial cofactor for numerous enzymes that catalyse the metabolism of proteins, fats, and carbohydrates. A significant portion of Mn is found in the mitochondria, where it activates several metal-enzyme complexes that control carbohydrate metabolism, including pyruvate carboxylase. By aiding in the synthesis of fatty acids and cholesterol, manganese also serves as a cofactor in lipid metabolism. Less than 10% of the dietary intake of manganese is absorbed, which is a very low percentage. A surplus of dietary Ca or P prevents the absorption of Mn. Transferrin serves as a carrier for the manganese, which is absorbed from the digestive tract as Mn²⁺, oxidised to form Mn³⁺, and then transported to tissues. A diet high in Mn can cause an iron deficiency.

 

Zinc

The animal body contains a lot of Zn. The liver, bones, and animal body coverings like hair, wool, skin, and feathers all contain significant amounts of zinc.

In the body of an animal, more than 100 different enzyme systems require zinc as a cofactor or constituent (metalloenzyme). These include enzymes that produce proteins and nucleic acids as well as those that metabolise them (like DNA and RNA polymerases). The distribution of enzymes to which zinc is related in the tissue has a strong correlation with the concentration of zinc there. Since Zn is a part of insulin, it contributes to the metabolism of carbohydrates. Zn is necessary for the production of retinol-binding proteins and is crucial for T-cell immunity and reproductive health. Zn is absorbed between 5% and 40% of the amount consumed, depending on several variables.

The transfer of zinc from intestinal mucosa cells to plasma and the metabolism of zinc are both facilitated by the low molecular weight binding protein known as metallothionein, which has a high affinity for binding to zinc. Zn is bound and trapped inside the mucosal cells by metallothionein, which is produced in response to high Zn concentrations.

 

Iron

All of the animal body’s cells contain Fe, but the majority of it is found in the protein molecules myoglobin (> 4%) and haemoglobin (> 65%) as a component. In red blood cells, haemoglobin is a complex protein that consists of a haem group (porphyrin) that contains ferrous (Fe²⁺) iron and a protein (globin). The synthesis of respiratory pigments (haemoglobin), which are necessary for carrying oxygen from the lungs to tissues, is the metabolic use of iron.

 

Copper

Haematopoiesis, or the production of red blood cells, requires Cu. Iron and copper metabolism are therefore closely related. Different enzyme systems use copper as one of their constituents. This includes the lysyl oxidase required for the cross-linking of collagen and elastin. Major vessels may rupture as a result of inadequate crosslinking, and bone matrices may be damaged. Cytochrome C oxidase, which is involved in electron transport and ATP production, contains copper as one of its constituents. The plasma protein ceruloplasmin is where the majority of the copper present in the blood is bound. In addition to serving as a Cu carrier, this Cu-dependent protein is required for plasma iron to bind to transferrin. Additionally, copper is a part of the antioxidant enzyme superoxide dismutase, which neutralises free radicals and guards against cell death and membrane damage. Tyrosinase, an enzyme that transforms the amino acid tyrosine into the pigment melanin, requires copper to function. Lack of copper can result in inefficient melanin formation and lack of pigmentation, which can change the colour of a coat and cause wool (steely wool) to lose its crimp. Ruminant animals’ immunity is improved by a Cu supplement.

 

Selenium

A component of glutathione peroxidase, which deactivates lipid peroxides produced as a result of lipid oxidation, is selenium. In preventing the peroxidation of polyunsaturated fatty acids in cell membranes and preserving cell integrity, Se shares this property with vitamin E. Se and vitamin E thus have a moderating effect on each other’s micronutrient requirements. Se can also be found in blood and muscle as a component of other seleno-proteins. Seleno-protein is required for the sperm midpiece. As the deiodinase that changes the thyroid hormone thyroxine into its metabolically active form, triiodothyronine, Se is also involved in thyroid gland functions. Amino acids containing sulphur are crucial for Se metabolism. In their S-containing amino acid synthesis, rumen microbes switch out Se for S, and these amino acids are then absorbed in the duodenum. Seleno-methionine and seleno-cysteine are the storage forms of Se.

 

Cobalt

The mineral Co is a part of vitamin B12. The liver, kidneys, and bones are just a few of the tissues that contain cobalt. It is unknown how it manifests in tissues in forms other than as a component of vitamin B12. The symptoms of cobalt deficiency are similar to those of vitamin B12 deficiency due to cobalt’s close relationship as a chelated mineral with B12. Reduced ruminal B12 synthesis is caused by a diet low in cobalt. Animals that are ruminants require a lot of cobalt. This is brought on by their poor capacity for vitamin B12 absorption and ineffective vitamin B12 synthesis. Ruminant animals lacking cobalt (and vitamin B12) are unable to metabolise volatile fatty acids (propionic acid) for energy production; as a result, affected animals have high blood levels of propionate and have decreased appetites that cause emaciation. As blood glucose’s precursor, propionate, the animals affected will experience hypoglycaemia. Different regions of the world experience cobalt deficiency in the soil, which results in low levels of cobalt in the forages consumed by grazing ruminants. Cobalt-deficient ruminants receive oral administration of dense cobalt pellets. These pellets settle in the rumen and provide cobalt for rumen microbes necessary for the synthesis of vitamin B12. Since inorganic Co is very poorly absorbed from the GI tract, toxicity is unlikely as a result of this low absorption rate.

 

Iodine

The only known use for iodine is as a component of the thyroid hormones thyroxin (tetra iodothyronine) and triiodothyronine. The thyroid gland produces tetra iodothyronine, which is then released into the tissues and changed into triiodothyronine, the active form. Thyroglobulin, a protein containing iodine, is the precursor to thyroxine. Thyroxine regulates the basal metabolic rate and stimulates cellular oxidative processes. The highest concentration of I is found in the thyroid gland, which is followed by the stomach, intestine, mammary glands, and skin. The thyroid gland is a crucial component of I metabolism. The thyroid gland contains more than 80% of the iodine in the entire body. Thyroid-stimulating hormone (TSH), which is released by the anterior pituitary gland, facilitates the uptake of I by the thyroid. Thyroglobulin, a glycoprotein, is the primary form of iodine storage in the thyroid gland.

 

Molybdenum and Chromium

In addition to the microminerals discussed, several other elements have been shown to have positive effects on animal growth, immunity, and health. These include molybdenum and chromium.

The cofactor Mo is a component of the nitrogenase and xanthine oxidase enzymes. Mo is applied to pastures as fertiliser. Mo toxicity is quite common, but Mo deficiency is extremely uncommon. A surplus of Mo prevents the uptake of copper and binds copper in the blood to form an insoluble complex, which results in a copper deficiency.

Animals have been found to require the mineral Cr as a vital nutrient. It has been determined that Cr plays a part in glucose metabolism and the uptake of glucose by cells. The supplementation of Cr has been shown to improve immunity and decrease respiratory disease in cattle, and it is used as a feed additive in swine nutrition to reduce carcass fat.