Animal Nutrition- 3
Terms
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- Energy
- capacity to do work
- Metabolism
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sum of all chemical transformations that occur in the cell/organism
occurs in series of enzyme catalyzed reactions that constitute metabolic pathways - Anabolism
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synthesis of lipids, polysaccharides, proteins, and nucleic acids
endergonic- require input of energy from hydrolysis of ATP and reducing power of NADPH and NADH
Ex:
amino acids, sugars ,fatty acids, butrogenous bases--->proteins, polysaccharides, lipids, nucleic acids
ATP, NADH, NADPH--->ADP+, NAD+, NADP+ - Catabolism
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break down to lactic acid, CO2, NH3)
Exergonic- release of free energy that is turned into ATP and reduced electron carriers (NADH, NADPH)
Ex:
Carbohydrates, fats, proteins---> CO2, H2O, NH3
ADP+-->ATP - ATP (adenosine triphosphate)
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most important
carries chemical energy between metabolic pathways by serving as a shared intermediate coupling endergonic and exergonic reactions - NADP (nicotinamide adenine dinucleotide phosphate)
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coenzymes functioning as carriers of hydrogens and electrons in same oxidation- reduction reactions
contains nicotinamide - FAD (flavin adenine dinucleotide)
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coenzyme of some oxidation- reduction reactions
contains riboflavin - Energy Balance
- amount of nutrient consumed sufficient to maintain weight
- Forms of Energy
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chemical- photosynthesis
mechanical- muscle movement - Autotrophs
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photosynthetic bacteria and higher plants
Use CO2 from atmosphere as source of carbon from which they construct all carbon-containing compounds (sugars) - Photo- Autotrophs
- depend on light to construct carbon containing biomolecules
- Heterotrophs
- must obtain carbon from environment in form of complex organic molecules
- Importance of energy in animal metabolism
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1. required in larger amount than any other nutrient
2. most often limiting factor in livestock production
3. major cost associated with feeding animals
*animal NOT EFFICIENT at transforming feed energy into its own body energy - Methods of measuring energy value of feedstuff
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1. Total digestible energy
2. starch equivalent
3. caloric system (current system) - Total Digestible Nutrient System (TDN)
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Digestibility
Computation of digestible nutrients:
[Digestible protein(protein+fiber+nitrogen free extract)+(fatx2.25)]
*multiply fat by 2.25 because there is 2.25 times more energy in fat than carbs.
*digestible protein= protein consumed-protein in feces
TDN usually expressed as percent of ration/units of weight - Advantage of TDN System
- used for a long time and many people are used to this system
- Disadvantages to TDN System
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TDN is a misnomer (not actual value of TDN)
does not include minerals
based upon chemical determinations and not related to actual metabolism of animal
expressed as weight/% whereas energy expressed in calories
considers only digestive losses and does not take into account losses in urine, gasses, and increased heat production - Feed Energy in Animal Systems
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Poultry:
true digestibility difficult to measure because undigested residues and urinary wastes are excreted together
convenient to determine metbolizable energy of a diet by pooling excreta as a single material representing unutilized portion of the feed energy - Energy Partition Scheme: Pigs
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DE system preferred because:
easy to measure
gaseous products from pigs considered to be insignificant and are ignored
ME=.96DE - Energy Partition scheme: Ruminants
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ME System:
considers gaseous lost
NE System (preferred):
animal requirements stated as net energy are independent of the diet
feed requirement for maintenance are separate from feed needed for productive functions - Partition of ME in the Growing Animal
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some species more efficient than others
some individual within species more efficient than others
as we age, out metabolism slows and we gain more fat
optimum stage for slaughter: when animal is most lean- before too much fat accumulates - Basal metabolim
- heat production from a healthy animal achieved when it is not given feed for some time and is kept in a thermoneutral environmet with a minimum of activity
- Maintenance Metabolism
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fed animal in stable weight and chemical composition over a period of time
Maintenance heat production is always HIGHER than basal metabolism because of the process of eating and digesting and metabolizing feed requires energy produced as heat - Contributers to heat production
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1. factors relating to the processing of the diet by the animal:
work done in location (ex. animal goes to hunt), prehension, and mastication of food
work done by movement of digestive tract
heat of fermentation of certain dietary constituents
heat increment associated with metabolic processing of nutrients
2. Factors associated with non food related ativities:
maintain body temp.
work of circulation, respiration, maintenance of posture, standing, and locomotion
energy cost of basic metabolic processes, including tissue turnover - Direct Calorimetry
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animal confined in well-insulated chamber and heat losses by:
radiation, convection, and conduction from body surface
evaporation of water from skin and lungs
evaproation of water and feces by increase in temp. in known volume of water and electrical current generated as heat passes across thermocouples
Most accurate method of measuring heat production of animals, but EXPENSIVE - Indirect Calorimetry
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heat production calculated from measurement of respiratory exchange:
O2 consumption, CO2 production
Respiratory Quotient= CO2 produced/O2 consumed - Starch Equivalent
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Expressed energy values of feeds relative to net energy value of common feed constituent, starch
SE= energy value of feed/energy value of starch - Units of Energy
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Calorie: units of heat used to describe energy yielding capability of foods on complete combustion
Calorie= amount of heat required to raise 1g pure water 1C.
1calorie=4.184 Joules
1000calories=1C=1kcal - Caloric System
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Gross Energy (GE)- total energy in feedstuff
Digestible Energy (DE)= total energy in feed-energy in feces
Metabolizable Energy (ME)
Net Energy (NE)= used for maintenance and growth
NEm (energy used for maintenance only)
NEp (energy used for production only) - Gross Energy (GE) of Feed
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heat henerated when a unit mass of feed is completely combusted in oxygen to yield carbon dioxide and water under standard conditions of temp. and pressure.
heat combustion measured by combustion calorimeter - Digestible Energy (DE)
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GE of feed consumed- GE of feces
DE values of no use in avian because uric acid is all together - Metabolizable Energy (ME)
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GE-fecal E-Urinary E-Gaseous products
Most common method used for poultry - Net Energy (NE)
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ME+heat increment+ NEm+ NEp
Very accurate measure of E value of feed
Difficult to determine - Heat Increment of Feed
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Heat released through body:
- muscle contraction
- digestion of food and metabolism of nutrients derrived from them
*act of chewing= ~3-6% ME intake
1.Chewing
2.Swallowing
3.Metabolism of gut microflora in ruminents (7-8% ME intake)
4.Secretion of Saliva - Thermodynamics
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1. Endergonic: energy must be added, can end up with more energy
2. Exergonic: give off energy
*both types of reactions often occur together (coupled) - Bioenergetics
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1. chemical conversion of feedstuff into biological E
2. this conversion sustains life
3. Conversion occurs within cells - First law of Thermodynamics
- total energy in universe remains constant, but may change form
- Sources of energy
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Macro-Nutrients:
1. Carbohydrates: C,H,O
2. Fats: a lot of C&H, some O
3. Proteins: C,H,O,N,S - Carbohydrates
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1.Monosaccharides: glucose, fructose
2.Disaccharides: sucrose (glucose&fructose), Maltose (glucose & glucose)
3. Polysaccharides: plant or animal source, glycogen mose common
*brain depends only on glucose for survival - Fats
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1g=9kcal of energy
insoluble in water
4 Groups:
fatty acids- stored as triglycerides in adipose tissue
triglycerides- 3 fatty acids and glycerol
phospholipids- structure, insulation of nerves
steroids- cholestrol and hormones - Proteins
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1g= 4kcal
made up of 20 amino acids
9 amino acids are essental
must be broken down to amio acids then used for energy
easily converted to glucose - Bio-Energetic Pathway
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1. Anerobic- glycolysis
2. Aerobic- glycolysis, TCA/Kreb cycle, electron transport system - ATP
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adenosine, ribose, and phosphates
may form from AMP or ADP
breakage of phosphate bonds by ATPase releases energy - NAD/FAD
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1. Glycolysis:
2 NADH formed
electron carriers
pyruvate
lactic acid
*cyanide stops electron transport chain instantly