Nutrition is the series of process by which an organism takes in and assimilates food for promoting growth and replacing worn-out or injured tissues.
A nutrient is any feed constituent or group of feed constituent of the same general chemical composition that aids in the support of life.
Digestion is the breakdown of feed particles into suitable products for absorption.
Absorption is the transfer of substances from GIT to the circulatory (blood or lymph) system.
A metabolism is the combination of anabolic and catabolic reactions occurring in the body with the liberation of energy.
Enzymes is a complex protein produced in living cells that causes changes in other substances within the body without being changed itself (organic catalysts).
Classes of nutrients
Water – the cheapest and most abundant nutrient. It makes up to 65-68 % of animal BW at birth and 45-60 % of BW at maturity.
- accounts 90-95 % of blood and many tissues contain 70-90 % water
- found in:
1. Intracellular water – mainly muscles and skin
2. Extracellular water – mainly interstitial fluids, blood plasma, lymph, synovial and cerebrospinal fluids.
- functions:
1. transport of nutrients and excretions
2. chemical reactions and solvent properties
3. body temperature regulation
4. maintain body cells
5. lubricates and cushion joints and organs in the body cavity
- deficiencies:
1. reduced feed intake and palatability
2. weight loss due to dehydration
3. increased secretions of N and electrolytes such as Na and K
Carbohydrates – made up of C (40 %), H (7 %) and O (53 %). It makes up approximately ¾ of plant dry weight and thus the largest part of animals food supply.
- formed by photosynthesis
- classification:
1. Monosaccharide – includes hexose (glucose, fructose, galactose) and pentose (arabinose, xylose, ribose)
2. Disaccharide – includes sucrose, maltose, lactose, cellobiose
3. Polysaccharide – includes starch (amylase, amylopectins, glycogen), cellulose, mixed polysaccharide (hemicellulose, pectin), and lignin
- functions:
1. source of energy
2. source of heat
3. building stores for other nutrients
4. stores in animal body by converting to fats
- deficiencies:
1. ketosis
2. diabetes mellitus
Fats (lipids or ether extract) – made up of C (77 %), H (12 %), and O (11 %). It is insoluble in water but soluble in organic solvents.
- fat will yield 2.25 times more energy than CHO or proteins
- classifications:
1. Simple lipids
2. Compound lipids – includes phospholipids (phosphoric acid and nitrogen), glycolipids, and lipoproteins
3. Derived lipids – includes fatty acids and sterols
- functions:
1. dietary supply
2. source of heat, insulation and protection for animal body
3. source of essential fatty acids (linoleic, linolenic and arachidonic acid)
4. serve as carrier for absorption of fat soluble vitamins
- deficiencies:
1. skin lesions, hair loss and reduced feed growth rate
2. ketosis (catabolism of body fat)
3. fatty liver (abnormal metabolism of liver)
Proteins – made up of C (53 %), H (7 %), O (23 %), N (16 %) and P (1 %). It is the principal constituents of the organ and sifts structures of the animal body.
- true proteins, composed of amino acids
- non-protein nitrogen (NPN), not true protein in nature but contain N and can be converted to protein by bacterial action, e.g. urea
- crude proteins (CP), composed of true proteins and any nitrogenous products (CP = % N x 6.25)
- protein quality refers to the amount and ratio of essential amino acids present in protein.
- classifications of proteins:
1. Simple (globular) proteins – yielding only amino acids or their derivatives upon hydrolysis, e.g. albumins, histones, protamines, globulins, glutelins, and prolamins
2. Fibrous proteins – constitute about 30 % of total protein in animal body, connective tissue, e.g. collagens, elastin, keratins
3. Conjugated proteins – a simple proteins are combined with non-proteins radical, e.g. nucleoprotein, glycoprotein, phosphoproteins, hemoproteins, lecithoproteins, lipoproteins, metalloproteins.
- functions of proteins:
1. basic structural unit of the animal body
2. body metabolisms
- classifications of amino acids:
1. Essential amino acids – those amino acids which are essential to the animal and must be supplied in the diet because the animal cannot synthesize them fast enough to meet its requirements. Examples: phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, histidine, arginine, leucine, lysine
2. Non-essential amino acids – those amino acids which are essential to the animal but are normally synthesized or sufficient in the diet and need not be supplement. Examples: alanine, asparagines, aspartic acid, cysteine, cystine, glutamic acid, glutamine, glycine, hydroxyproline, praline, serine, tyrosine
- deficiencies:
1. reduced growth rate and feed efficiency
2. anorexia
3. infertility
Minerals – are inorganic solids, crystalline chemical elements. It makes up 5 % of an animal body on dry weight basis.
- ash, total mineral content of plants or animals
- functions:
1. skeletal formation and maintenance
2. protein synthesis
3. oxygen transport
4. fluid balance (osmotic pressure)
5. regulating acid-base balance of enzyme systems
6. activators and/or component of enzyme system
7. mineral-vitamin relationship
- classifications:
1. Major mineral or macro minerals – normally present at greater level in animal body or needed in large amounts in the diet.
- examples:
a. Sodium and chlorine – for formation of digestive juices, control of body fluid concentration, control of body fluid pH, and nerve muscle activity.
deficiency:
• unthrifty appearance and impaired performance
• disrupted nerve and muscle function
• nervous prostrations
b. Calcium – for bone and teeth formation, nerve and muscle function, acid-base balance, and milk production and egg production
deficiency:
• rickets
• osteomalacia or osteoporosis
c. Phosphorus – for bone and teeth formation, component of protein in the soft tissues, milk production and egg production, and metabolic processes.
deficiency:
• rickets
• osteomalacia or osteoporosis
• poor appetite, slow gain, lowered milk production, low blood phosphorus and unthriftiness
• animal may eat soil and chew on nonfeed objects
d. Magnesium – necessary for many enzyme systems, play as a role in CHO metabolisms, and necessary for the proper functioning of the nervous system.
deficiency:
• hypermagnesemic tetany – hyper-irritability of neuromuscular system producing hyperexcitability, incoordination and frequently death
e. Potassium – for osmotic pressure, acid-base balance, rumen digestion, and intracellular cation in neuromuscular activity
deficiency:
• decreased feed consumption
• lowered feed efficiency
• slow growth
• stiffness
• emaciation
f. Sulfur – for component of the amino acid (cystine and methionine) and vitamins (biotin and thiamine), synthesis of sulfur containing amino acids in the rumen, and the formation of various body compounds
deficiency:
• protein deficiency – general unthrifty conditions and poor appearance
2. Minor/trace or micro minerals – normally present at low levels in animal body or small amount in the diet.
- examples:
a. Iron – necessary for hemoglobin formation, essential for the formation of certain enzymes related to oxygen transport and utilization, and formation of certain compounds which serve iron stores in the body, e.g. ferritin (found primarily in the liver and spleen) and hemosiderin (found mainly in the blood)
deficiency:
• low blood hemoglobin
• labored breathing
• listlessness
• pale eyelids, ears and nose
• flabby, wrinkled skin
• edema of head and shoulder
b. Iodine – for production of thyroxine by the thyroid glands.
deficiency:
• goiter at birth or soon thereafter
• dead or weak at birth
• hairlessness at birth
• infected navels esp. foals
c. Cobalt – for component of Vit. B12 molecule and rumen synthesis of Vit. B12.
deficiency:
• poor appetite
• unthriftiness
• weakness
• anemia
• decreased fertility
• slow growth
• decreased milk and wool production
d. Copper – for iron absorption, hemoglobin formation, synthesis of keratin for hair and wool growth, and various enzyme systems.
deficiency:
• low blood and liver copper
• bleaching of hair in cattle
• abnormal wool growth in sheep
• abnormal bone metabolism
• muscular incoordination
• weakness at birth
• anemia
e. Fluorine – for reduces incidence of dental caries, and retards osteoporosis in mature animals.
deficiency:
• excessive dental caries esp. children
f. Manganese – for influencing estrus, ovulation, fetal development, udder development, milk production, and growth and skeletal development.
deficiency:
• delayed estrus
• reduced ovulation
• abortions
• resorptions
• deformed young
• poor growth
• lowered serum alkaline phosphates
• lowered tissue manganese
• knuckling over in calves
g. Selenium – for Vit. E absorption and utilization, component of enzyme (glutathione peroxidase – destroy toxic peroxide in the tissues thereby having a sparing effect in the Vit. E requirement), and maintenance of normal cell functions and membrane health.
deficiency:
• muscular dystrophy (white muscle disease)
• retained placenta in cows
• heart failure
• paralysis
• poor growth
• low fertility
• liver necrosis
• pancreatic fibrosis in chicks
h. Zinc – prevents parakeratosis, promotes general thriftiness and growth, promotes wound healing, related to hair and wool growth and health, and deficiency impairs testicular growth function.
deficiency:
• parakeratosis
• general thriftiness
• poor growth
• unhealthy looking hair or wool
• slow wound healing
Vitamins – is organic components of natural food. It is present in foods in minute amounts and effective in small amounts. It is also essential for development of normal tissue necessary for metabolic activity but do not enter into structural portion of the body. Other function is necessary for growth and maintenance.
- cannot be synthesized by the animal
- related substances:
1. Provitamins or precursors (carotene)
2. Antivitamins, vitamin antagonists or pseudovitamins
- 2 forms of vitamins:
1. Fat-soluble vitamins – can be dissolved in fats
a. Vitamin A – is also known as retinol. It promotes the development of visual pigments. It is indispensable for the formation of epithelial tissues and improves the resistance to infection.
b. Vitamin D – also known as calciferol. It regulates the incorporation of Ca and P into the bone matrix and the Ca absorption from the intestinal lumen.
c. Vitamin E – also known as tocopherol. It works as a biological antioxidant (detoxifying agents). It participates as a component of the respiratory chain and function in nucleic acids metabolisms and in endocrine glands.
d. Vitamin K – also known as menadione. It functions in the blood coagulation system. It acts in the maturation of the bone structure.
2. Water-soluble vitamins – can be dissolved in water
a. Vitamin B1 – also known as thiamin. It participates in the process of carbohydrate metabolisms.
b. Vitamin B2 – also known as riboflavin. It acts in the respiratory chain as a constituent of the flavin enzymes concerned with H transfer.
c. Vitamin B6 – also known as pyridoxine. It is active in amino acids metabolisms as a coenzyme of several enzyme systems.
d. Vitamin B12 – also known as cyanocobalamin. It is essential in the reduction of one carbon compounds in the fat and protein metabolisms.
e. Biotin – also known as Vit. H. It is necessary for gluconeogenesis and fatty acid synthesis where it acts in carboxylation reactions.
f. Folic acid – it acts in the one carbon metabolisms where it is indispensable in the formation of amino acids and nucleic acids.
g. Nicotinic acid – also known as niacin or nicotinamide. It acts as an active group of different coenzyme which is related to the citric acid cycle.
h. Pantothenic acid – part of coenzyme A which occupies a central position in the intermediary metabolisms by activating weakly active acids.
i. Vitamin C – also known as ascorbic acid. It is essential in the formation and maintenance of skeletal tissues. It participates as an oxidation-reduction system in cellular oxidation processes and also involved in defensive mechanisms.
- vitamin deficiency in poultry:
1. nervous disorders such as convulsions
2. skin or mouth lesions
3. discharge from eyes or swollen, pasted eyelids
4. reduced resistance to infectious diseases
5. poor feathering
6. bone abnormalities
7. leg weakness or paralysis
8. egg production reduced or below full potential
9. retarded growth
10. hatchability reduced or below full potential
- vitamin deficiency in pigs:
1. muscular incoordination of other nervous signs
2. reduced feed intake
3. impaired vision or blindness
4. scours and/or vomiting
5. hair, skin and claw problems
6. anemia
7. impaired feed conversion
8. lameness or unsteady gait
9. poor reproduction
10. retarded growth
11. weakness or increased mortality of newborn pigs
- vitamin deficiency in ruminants:
1. muscular incoordination or other nervous signs
2. reduced feed intake
3. impaired vision or blindness
4. digestive disturbances
5. rough hair coat
6. degeneration of heart and skeletal muscle
7. poor reproduction
8. retarded growth
9. bone deformities or swollen joints
Unit 4: Digestive Systems and Absorption of Food Nutrients
The digestive system consists of the teeth, mouth, gullet (esophagus), stomach, liver, intestine, pancreas, and rectum.
Digestion begins in the mouth where feed is broken down into small pieces by the teeth and mixed with saliva before being swallowed.
In the stomach feed is mixed with the juices to form a soft paste. This then passes into the intestine where bile from the liver and juices from the pancreas are added. The action of these juices is to break down the feed and allow the nourishment it contains to be absorbed by the blood in the walls of the intestine. Waste matter collects in the rectum and passes out of the body through the anus (or cloaca in birds).
Splanchnology is the name of the study of digestive system.
Animal’s carnivore, omnivore and herbivores
Animals are divided into three groups:
Carnivores which eat meat, e.g. dog, lion
Omnivores which eat meat and plants e.g. pig
Herbivores which eat plants e.g. cow, horse
The digestive system of omnivores and carnivores is as described above. In herbivores the digestive system is very large because they eat large amounts of grass.
- The horse, donkey and mule are herbivores but do not chew the cud. They are non-ruminants.
- Cattle, goats, sheep and buffalo chew the cud. They are ruminants.
Digestion – includes 2 processes the mechanical process and chemical process. The mechanical process includes chewing (mastication) and muscular contractions of the GIT. The chemical process involves the action of acids in the GIT or enzymes produced by the microorganisms located in various parts of the GIT.
- types of GIT:
1. Non-ruminant or simple stomach
2. Ruminant or compound stomach
3. Avian type or modified-simple stomach
Non-ruminant
- includes the pigs, horse, rabbit, dog and cat and humans
- major parts includes the mouth, esophagus, stomach, small intestine, large intestine
Mouth – consists of tongue (grasping food), teeth (mastication of food), and salivary gland (produce saliva which contains water to moisten food, mucin to lubricates food for easy swallowing, bicarbonates salts to buffer or regulate pH and salivary amylase to start CHO digestion).
Esophagus – a muscular tube. It allows passage of food from mouth to stomach.
Stomach – a muscular digestive organ. It is for storage of ingested feed, mechanical breakdown, and production of HCl, enzymes and mucus.
- 3 regions:
1. Cardiac – cells produce mucus that protects the stomach lining.
2. Peptic – cells produce HCl, pepsin (proteolytic enzyme) and mucus.
3. Pyloric – mucus producing cells.
Small intestine – has 3 divisions, namely:
1. Duodenum – first section that is very active site of digestion that receives secretions from pancreas, liver, and intestinal walls.
2. Jejunum – middle sections that involved in nutrient absorption.
3. Ileum – last section that also involved in nutrient absorption.
Large intestine – has 3 sections, namely:
1. Cecum – first section that is large in horse and rabbit and well developed as in the horse that contains many bacteria which produced enzymes that digest fiber.
2. Colon – middle section that involved in reabsorption of water.
3. Rectum – last section
Ruminants
- includes the cattle, sheep, goat and carabao
- 4 compartment stomachs:
1. Rumen – large muscular compartment which fills the left side of the body cavity. It is also called paunch.
- has papillae that covered by projections for absorptions of nutrients
- provide favorable environment for protozoa and bacteria
- pregastric fermentation produces enzymes that breakdown fiber as well as starch and protein, and volatile fatty acids (VFA) such as propionic acid, butyric acid and acetic acid.
- water soluble vitamins and vitamin K
- bacterial synthesis of amino acids and protein
- favorable conditions:
a. anaerobic environment
b. constant warm temperature
c. moisture
d. constant food supply
e. mixing
f. removal of toxic end-products
- additional functions:
a. storage
b. soaking
c. physical mixing and breakdown
2. Reticulum – also called honeycomb. The main function is to move food into the rumen or omasum and collect of dense particles of food and in regurgitation of ingesta during rumination.
- rumination, movement of ingesta back up the esophagus to the mouth for additional mechanical breakdown (chewing the cud)
3. Omasum – is a round muscular organ which contains many muscular laminae. It is also called many fold or many plies.
- functions:
a. controlling passage of ingesta to lower tract (act as pump)
b. reduce particles size of ingesta
c. absorption
4. Abomasums – also called as true gastric stomach. It is identical to the gastric stomach of non-ruminants.
- small intestine and large intestine is similar in form and functions as in the non-ruminants
- additional features in ruminants:
1. Esophageal groove – found at the base of the esophagus and when stimulated by sucking forms a tube which empties into the abomasums. The main function is to direct milk obtained from sucking to escape microbial digestion in the rumen.
2. Rumination – described as controlled vomiting. It is control set of contractions of esophagus, reticulum, and rumen that allows ingesta to be swallowed regurgitated back up to the esophagus where fluids swallowed again. It has additional remastication and reswallowing of solids.
3. Eructation – belching of gas. It is removal of large volumes of gas produced in the rumen. It is contractions of the upper part of the rumen force the gas up the esophagus and from there the gas penetrates into the trachea and lungs.
When the ruminant has finished eating, the food is brought back up and rechewed. This is called chewing the cud or rumination. If the animal stops ruminating this is a sign of ill health.
Ruminants make a lot of gas in their stomachs and belch once every minute, (unlike people they belch silently). If the belching stops the stomach swells with gas. We call this bloat or tympany.
The rumen moves regularly and contracts about once every minute. By putting your fist on the left flank (in the hollow behind the ribs) you will be able to detect the contractions. Regular contractions are a sign of good health.
Avian type
– consists of beak, crop, proventriculus, ventriculus, small intestine and large intestine, e.g. all birds.
Beak – collects particles of feed and breaks some large particles into smaller pieces. The tongue and salivary glands are present and saliva does not contain salivary amylase.
Crop – enlarged area that connected to the esophagus. The functions are for temporary storage and moistening of food, place for salivary amylase to work, and microbial fermentation in some species.
Proventriculus – true stomach of birds. It is the site of HCl and pepsin production. The ingesta pass through the proventriculus very rapidly (14 seconds).
Ventriculus – commonly called gizzard. It is muscular area that contains grit. The muscular contractions which are involuntary aid in the mechanical breakdown of food and it is similar to the mastication by the teeth in the non-ruminant and ruminant.
Small intestine – it is similar to the small intestine of the non-ruminant and ruminant.
Large intestine – has 2 areas (called ceca) which are very similar in form and function to the cecum of non-ruminant and ruminants.
The bird has no teeth, food is swallowed whole and goes into the crop where it is stored and mixed with saliva. If you feel the crop you can tell if a bird has been feeding or not.
The feed passes from the crop into the stomach where it mixes with the juices before passing into the roundish, thick walled, muscular organ called the gizzard. The gizzard contains small stones which the bird has eaten to help the gizzard to grind up the food for digestion. Nutrients are absorbed as ground up feed passes along the intestine.
Birds do not produce liquid urine. Waste from the kidneys forms a thick white material which is mixed with the feces (droppings). Both are then passed out through the cloaca. The duck produces wetter droppings than the chicken.
Nutrient digestion
Nutrient Basic unit
Protein ---------------------------------------------------------- amino acids
Starch -------------------------------------------- glucose (non-ruminant), VFA and lactic acid (ruminant)
Cellulose ------------------------------------------------------- VFA
Sucrose -------------------------------------------------------- glucose and fatty acids
Lactose ------------------------------------------------------- glucose and galactose
Lipids ---------------------------------------------------------- fatty acids and glycerol
Minerals ------------------------------------------------------- any soluble form
Vitamins ------------------------------------------------------- any soluble form
End products of enzymes
1. Saliva
- salivary amylase, starch to maltose
2. Rumen
- microbial cellulose, cellulose to VFA
- microbial amylase, starch to VFA and lactic acid
- microbial proteases, protein to amino acids and NH3
- microbial urease, urea to CO2 and NH3
3. Stomach, abomasums, proventriculus
- pepsin, protein to polypeptides
4. Pancreas
- trypsin, protein to peptides and amino acids
- chymotrypsin, protein to peptides and amino acids
- carboxypeptidase, protein to peptides and amino acids
- amylase, starch to maltose
- lipase, lipids to fatty acids and glycerol
5. Small intestine
- aminopeptidase, protein to peptides and amino acids
- dipeptidase, peptides to amino acids
- maltase, maltose and glucose
- lactase, lactose to glucose and galactose
- sucrase, sucrose to glucose and fructose
Absorption – occurs primarily in small intestine.
- villi, small projections which line the small intestine
- papillae, projections which line the rumen (VFA)
- occurs as the result of diffusion or active transport
- diffusion, movement of the basic units from areas of high concentration (GIT) to area of lower concentration (blood)
Metabolisms – occurs only after basic units of nutrients have been absorbed into the blood. The chemical reactions performed by the cells to use the basic units of the nutrients for their specific functions (glucose – for energy and amino acids – for protein synthesis).
- reactions functions in series and are described as pathways or cycles:
1. Embden myerhof pathway of glucose metabolisms
2. Krebs cycle
- has two forms:
1. Anabolisms – building up of tissues
2. Catabolism – breaking down of tissues
Unit 5: Ration Formulation
Feeds – naturally occurring ingredients in the rations of animals that are used to sustain life.
Classification of feeds
1. Roughage – livestock feeds that contain more than 18 % crude fiber when dry.
- examples:
a. hay
b. silage
c. pasture
d. fodder
2. Concentrates – livestock feeds that contain less than 18 % crude fiber when dry.
- examples:
a. meat scraps
b. meat and bone meal
c. fish meal
d. blood meal
A ration is the amount of feed given to an animal to meet its needs during a twenty-four hour period.
A balanced ration is one that has all the nutrients the animal needs in the right proportions and amounts.
Ration formulation is a process of combining different feed ingredients to a proportion that will give the animals the proper amount of nutrients needed at their particular stage of production.
Important consideration in feed formulation
1. acceptability
2. digestibility
3. cost
4. presence of anti-nutritional factors and toxins
Methods of ration formulation
1. Pearson square method
2. Simultaneous equation method
3. Two-by-two matrix method
4. Trial-and-run method
5. Linear programming
Pointers in ration formulation
1. listing of nutrients requirements of animals
2. nutrient analyses of feed ingredients and cost to be used
3. usage and limitation of feed ingredients
4. check ration for each nutrient content cost/kg of mixed feed
Ration functions
1. Maintenance
- feed/ration or nutrients for the following purposes:
a. maintain BW or size
b. support essential life processes
c. maintain body temperature
d. maintain the different body secretions
- basal metabolisms or fasting catabolism, minimum energy expenditure to maintain essential life processes.
- energy requirement for maintenance is related to the body surface are or metabolic body size.
- activity increment, energy expenditure due to normal body movements and associated activities.
- protein requirement for maintenance is made up of two portions:
a. Endogenous urinary nitrogen (EUN) – normal wear and tear of the body organs and tissues
b. Adult growth functions – feathers, hairs, hoofs, nails
2. Growth
- correlated increase in the mass of the body to reach the size at maturity fixed by heredity.
- reflected in increased weight and size
- characterized by:
a. increase in the number of cells
b. increase in size of the cells
- optimum growth is in high protein level and good protein quality (essential amino acids)
- energy (CHO, fats, CHON) is the driving force for tissue synthesis or anabolisms
- high energy ration will make it faster and shorten the feeding or growth period
- low energy ration will slow down the growth rate and thus lengthen the growth rate
- ways of energy restrictions:
a. limit the total feed intake
b. lower the energy content or density of the ration
- energy to protein ratio is an important factor in the efficiency and economy of growth
- measures by the average daily (ADG) and feed efficiency affected by:
a. heredity (breed or strain of the animal)
b. environment (nutrition and management)
3. Reproduction
- nutrient requirement needed for:
a. female coming into estrus, subsequent conception and adequate development of the fetus until birth
b. males integrity of the reproductive organs and its sperm cells and sex hormones
- development of fetus (energy, CHON, Ca and P)
- severe deficiencies giving rise to low level of fertility by the following symptoms:
a. cessation of estrus
b. resorption of fetus
c. abortion
d. birth of dead or weak young
- principal nutrient deficiencies involved are protein, Ca, P and Vit. A
4. Milk production
- dairy type animals produce milk for human consumption and relatively very much less for the nourishment of their young
- temperate cows can yield 25-35 kg milk daily in 305 lactation period
- tropical cows can yield 8-12 kg daily
- genetics and climate (direct and indirect effects) have very much to do with this difference
- commercial dairying would generally need intensive grazing management or intensive forage production
- dairy cows need improved forages for efficient and economical production
- energy rather than crude protein seems to be the more critical problem in meeting adequate needs of the dairy cows in the Philippines
- concentrate would be needed to provide that energy deficit
- common rule of thumb, 1 kg of good concentrate mixture of every 2.5 kg of milk in excess of 5 kg if forage is of good quality
- milk constituents and blood sugars:
Casein ------------------------------------------------------ blood amino acids
Immune globulins ---------------------------------------- blood globulins
Fat ---------------------------------------------------------- fatty acids; acetate
Lactose ----------------------------------------------------- glucose
Minerals --------------------------------------------------- minerals in blood
Vitamins --------------------------------------------------- vitamins in blood
5. Egg production
- major factors affecting nutrient requirement :
1. rate of egg production
2. egg size or weight
3. egg shell thickness
4. body size of layer
- factors affecting egg shell quality is dietary calcium
- egg shell quality can be measured :
1. specific gravity of egg
2. shell thickness
3. shell smoothness
4. breaking strength
5. percentage of cracks or shell appearance
- low dietary calcium levels, less than 2 % decrease egg quality in chickens
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