nutrition Flashcards
Proximate Analyses def and made of
= analytical methods to assess
feedstuffs.
-made of
1 moisture
2 dry matter:
a.) organic matter: protein, fat, carbs, vitamins
b.) inorganic “ash” material:
minerals
proximate analysis steps
1: calculate dry matter DM
2: do ether extraction for either extract to measure fat
2: measure crude protein with kjeldhl procedure to measure nitrogen.
3: boil EE (either extract) in acid, and alkali to find Crude Fiber CF and Ash
4: Burn-> gives you CF & Ash
units of energy
- Kilocalorie = Energy required to raise the temperature of 1 kg of water 1 oC kcal
- The Calorie used in human nutrition is actually a kcal (Note that it
begins with a capital C)
Calorie=kcal for humans - Joule is used in Europe and scientific publications
(1 calorie = 4.18 joules)
1kcal =4.18 kjoules
Energy Partitioning
- How much energy is there in food?
- How much is available to the animal for biological processes?
- How can we measure it?
- We oxidize it (burn) and measure how much heat it gives off.
Bomb Calorimetry
- Measures the gross energy of a feedstuff
- GE is heat released when CHO, lipids and proteins in feedstuff are burned-off
- Feed + O2 = CO2 + H2O + HEAT
-marterial is burt in bomb calorimeter
Gross Energy (GE)
- The amount of heat released when a substance (feed) is
completely oxidized in a bomb calorimeter - GE = Heat of Combustion
ex. carb 4.2, fat 9.3.
-indigestible feedstuffs (ash, mineral, water) will have GE 0
-limitations of GE: doesn’t tell us if animal can digest it and need to account for energy losses.
Fecal Energy (FE)
- Some feed energy is not absorbed and instead is lost in feces
due to incomplete digestion. - FE = energy contained in feces measured using a bomb
calorimeter - Single largest loss of ingested energy
Digestible Energy calc
Digestible E = Gross E – Fecal E
Digestibility = (DE/GE) x 100
ex. FE= 10 kcal, GE = 100kcal
DE= 100-10=90kcal
digestibility= (90/100)x100=90%
Net energy NE
-the closest estimate of true
energy values because it takes the heat increment from
digestive process and metabolism of feeds into account.
Metabolizable energy
- Not all of the energy the animal absorbs stays in the animal
- Accounts for losses from:
- Urinary energy (urea, uric acid)
- Gaseous energy (methane, hydrogen, hydrogen sulfide, carbon
monoxide) - Gill energy (ammonia) fish
- Energy supplied by the feed that remains in the animal
for metabolism - ME = DE – (Urinary E + Gaseous E + Gill E)
-use any that are relevant to animal, could be all three
Excretion of nitrogenous wastes by birds
-why we measure ME in poultry
* Nitrogenous waste is excreted as uric acid in birds
* Excreted directly into the cloaca where it is mixed with feces
* Cannot separate fecal from urinary energy
Heat increment
- Accounts for energy lost as heat during digestion and
metabolism - Heat increment is the heat produced (energy used)
during digestion of feed, metabolism of nutrients and
excretion of waste. - Components of heat increment:
- Work of digestion
- Heat of fermentation
- Nutrient metabolism
-Heat increment = Total heat production fed – Total heat production fasting or this equation->
-HI = ME - NE
Net energy: calc, advantages, disad.
-accounts for heat increment lost during metabolism
NE = GE - FE – UrinaryE- GaseousE – Heat Increment
- Advantages:
- Takes account of the metabolic cost of nutrient metabolism
- Allows a better prediction of animal performance based on
diet formulation - Disadvantages:
- Expensive and time consuming to measure NE
Measurement of Heat Increment 2 ways
Direct Calorimetry:
* Heat production measured directly: animal in chamber
- Indirect Calorimetry:
- Use gaseous exchange (O2 consumption, CO2 output) to
estimate heat loss
-fuel + O2 –> CO2 + H2O+ HEAT
-if we account for how much CO2 produced we know how much heat produced per molecule of CO2
2 Components of Net Energy
NE= maintenance E + PE
Maintenance Component:
* Basal metabolism
* Thermoregulation
* Voluntary activity associated with
maintenance
Production Component:
* Growth
* Fat deposition
* Offspring
* Milk
* Eggs etc.
Measuring the energy of production of animals
- Growth: Measure the increase in the energy contained in the animal’s body
- Milk: Measure the energy content of the milk
- Egg: Measure energy content of the egg
Energy systems in different
species
- Pigs: DE for Urine, gaseous losses low
- Aquaculture: DE, Protein metabolism is very efficient
- Poultry: ME, Fecal + urine excreted together
- Ruminants, NE used, Gaseous losses, HI large
glucose in energy metabolism
-glucose levels are tightly regulated: important source of energy
-brain tissues cannot synthesize glucose so are dependent on blood glucose
-regulated by insulin and glucagon
insulin
-anabolic
-increaase glucose and amino acid uptake by cells
-stimulates the synthesis of glycogen in the liver, protien in muscle tissue and triglycerols in adipose tissue
after a meal metabolism
-carbs broken down to glucose, fructose, galactose then to glycogen or pyruvate.
-pyruvate to acetyl coA
-to krebs cycle then ETC
-glucose source is exogenous, all tissues are consuming and brain nutrient is glucose.
lipids as an energy source
-lipids broken down to FFA + triglyceride.
-then beta oxidation creates aceytl coA to krebs cycle then ECC
-gluconeogenesis can be possible from FA but only small amount from glycerol, and odd chin FA –> pyruvate.
energy during medium fast
-im medium fast after carbs are debleted lipids will start getting broken down through beta oxidation or to ketone bodies.
-gluconeogenesis can be possible from FA but only small amount from glycerol, and odd chin FA –> pyruvate.
-proteins are then broken down to AA and form a nitrogen pool and can have gluconeogenesis to create pyruvate. only glucogenic AA can create pyruvate. ketogenic AA make ketones.
-Glycogen and glyconeogenesis is source during medium fast, supplied by liver and muscle. Brain receiving glucose.
metabolism during starvation
-carbs and fat depleted, rely on protein pool maybe even lead to break down of skeletal muslce
-some make pyruvate–> glucose-> krebs
-other AA make ketone bodies.
-gluconeogensis is the source of glucose, consuming tissues are the brain, main source is glucose. Starvation is when you run out of all gluconeogenic and then fuel is ketone bodies.
Measuring Glycemic Index
-works well dogs, not cats
Standard area under glucose curve = 75 mmol · min
WARNING: Concept works well for omnivores, but not ruminants or carnivores
-take area under curve of test subject and divide by sample of glucose curve. take sample/ standard glucose curve= glycemic index.
-not true for production animals, if you feed higher glycemic index feed to production animals they will utilize and retain more nitrogen (protein)
high vs low glycemic
-high glycemic load meal–> high serum glucose and insulin–> rapid uptake of serum glucose and AA–> high fat and protein deposition (improves production and weight gain)
-low glycemic load meal–> low serum–> slow uptake of serum glucose and AA–> low fat and protein deposition (better in small animals)
Carnivores and glycemic responses
Carnivores have evolved to consume high protein, low carbohydrate diets:
* Have high rates of gluconeogenesis, even after a meal
* Some amino acids, particularly arginine, can stimulate insulin release
- Carnivores can appear ‘glucose intolerant’ if fed a high carbohydrate diet
- Postprandial hyperglycemia due to continued gluconeogenesis AND glucose
surge from meal - Tend to have very prolonged postprandial hyperglycemia
-domestic dogs have more carb enzymes to utilize carbs, domestic cats have not evolved as much.
The kind of starch in the diet affects insulin responses
- Rapidly digested carbohydrates stimulate a greater insulin response
- More anabolic
- Greater utilization of amino acids and fats by body tissues
different carb types 2 catagories
1 Glycemic carbohydrates/ available carb (host animal can digest)
* Glucose, sucrose, fructose, lactose
* Starch
2 Fibre (type of starch that can’t be digested)
* Cellulose
* Hemicellulose
* Etc.
starch
- Major storage carbohydrate in higher plants
- Polymers of glucose
- Two types
- Amylose
- Amylopectin
starch types amylose vs amylopectin
Amylose:
* Linear polymer of glucose
* Glucose residues attached by (α1-4) linkages
* Helical structure
* Slowly digested*** because helix is resistant to enzyme degradation, lower glycemic index
Amylopectin
* Branched polymer of glucose (α1-4) and (α1-6)
* Open structure is accessible to enzyme degradation
-rapidly digested, higher glycemic index
Fibre
1 soluble: pectin, gums, B-glucans some hemis
2 insoluble: lignin, cellulose, some hemis (bulk forming fibers stay in feces)
-act as structural carbs in plants (stem, husk of seeds. anything that isn’t readily digestible
cellulose
Long, linear polymer of repeating glucose units in β(1-4) linkage
Insoluble in water
Indigestible by vertebrate enzymes
hemicellulose
Heterogeneous group of polysaccharide substances
Sugars in backbone, side chains
Xylose, mannose, galactose (backbone)
Arabinose, glucuronic acid, galactose (side chains)
lignin
Highly-branched poly-phenolic polymer composed of phenol
units with strong bonding
Indigestible by mammalian, microbial enzymes
Plant content increases as plant matures
pectin
Complex group of polysaccharides called galacturonoglycans
Backbone = α(1-4)-linked galacturonic acid units
Sugar (xylose, galactose etc.) side chains
Microbial fermentation
B-glucans
Homo-polymers of glucopyranose units with β(1-4), β(1-3) linkages
Water-soluble, highly fermentable
Viscous intestinal fluid, interferes with digestion in poultry
B-glucanase added to poultry diets containing barley or oats
Used commercially as functional fibre
Reduce cholesterol, postprandial [glucose]
Soluble Xylans
- B-linked xylose backbone, arabinose side chains
- Causes poor nutrient digestibility in poultry
- Rye, wheat major sources
- Xylanase added to poultry diets
digestion of fibre
- Vertebrates do not have the digestive enzymes required to break down fibre
- Microorganisms can digest fiber via fermentation
steroids
- Include hormones, vitamins, structural components of cell membranes
Eicosanoids
- Carboxylic acids acting as second messengers in inflammatory responses
- Synthesized from highly unsaturated fatty acids
Triacylglycerols (fatty acids) def and nomenclature
- Esters of three carboxylic acids with glycerol
- The carboxylic acids are usually called fatty acids
- fat=triaclycerols
Fatty acid nomenclature
* Example: C18:3 n-3
* C18 means there are 18 carbon atoms in the fatty acid
* :3 means there are 3 double bonds in the fatty acid
* Fatty acids with double bonds are unsaturated, those with none are saturated***
* n-3 refers to the position of the first double bond from the methyl end of the molecule
* Also called omega-3
Saturated vs unsaturated fatty acids
- Saturated no double bonds
- Unsaturated 1 or more double bonds
- Polyunsaturated 2 or more double bonds
- These double bonds are in the –cis conformation
- Hydrogenation of fatty acids results in trans-fatty acids
-as you saturated fats they stay solid such as butter or lard, the more unsaturated the more liquid
fatty acids functions
- 3 Major Physiological Roles:
- Source of fuel
- Building blocks of phospholipids and glycolipids
- Precursors for hormones and intracellular messengers, signalling
- Stored as triacylglycerols (TAG)
digestion by pancreatic lipase
- Lipases hydrolyze triacylglycerols into 1 molecule of glycerol and 3 fatty
acid molecules
absorption of fatty acids
- Free fatty acids are again emulsified with
bile salts into micelles (small droplets) - Micelles diffuse into the epithelial cell
- No energy required
how fatty acids are transported into lymph system
- Triacylglycerols are reformed
- TAGs combine with proteins
- Chylomicrons are formed
- Chylomicrons diffuse into
lacteals in the lamina propria of
the villus
1 fatty acids and monoglycerides are emulsified by bile acids and form micelles
2 FA enter the epithelial cells and link to form tryglercerols.
3 triglycerides combine with proteins inside the golgi and form chylomicrons
4 chylomicrons enter the lacteal and are transported away from the intestine.
Transport of chylomicrons in the bloodstream
-after a fatty meal the lymph system will be full of chylomicrons and fat.
-then it enters bloodstream (chylomicrons and VLDLs) where lipoprotein lipase breaks them down to triglycerides where they can be used as energy( cholesterol to cells) or stored in adipocytes.
-HDL is the good cholesterol
-uptake via receptor mediated endocytosis
Storage of triacylglycerols in adipose tissue
-The fat reservoir of adipocytes is the main
energy storage in the body.
- Triacylglycerols are highly concentrated stores of metabolic energy
– More concentrated than proteins and CHO’s because they are anhydrous and
highly reduced - Complete oxidation of FA yields ~9 kcal/g
– ~4 kcal/g for CHO’s and Protein - TAG’s are stored in the cytoplasm of adipose cells
Intermediary Metabolism of TAGs
-FFA can be taken up by tissue, even number fatty acids can be broken down by acteyl co A into TCA cycle.
MCTs (medium-chain triglycerides)
- Defined as triacylglycerols with fatty acids that have 6-12 carbons
– C6, C8, C10. C12 - examples: Palm oil and coconut oil rich in MCTs
- these MCTs Fatty acids too short to easily be used for storage (in fat) or synthesis of essential fatty acids
- Catabolized for energy instead (keto diet!)
- Theoretically less likely to cause weight gain
Essential fatty acids
- Plants (usually) can only produce fatty acids with up to 18 carbons
- C18:2 n-6 Linoleic acid
- C18:3 n-3 Linolenic acid
- Animals require fatty acids with greater than 18 carbons for metabolites.
- They can elongate linolenic and linoleic acids to synthesize these fatty
acids (usually) - Linoleic and linolenic acids are therefore nutritionally essential in vertebrates
- Low in Western diets
- All vertebrates require 18:2 n-6 and 18:3 n-3
- These are the precursors for all highly unsaturated fatty acids (more than
18 carbons)
Fatty acids as precursors of hormones
- Eicosanoids are synthesized from
Arachidonic acid (20:4 n-6) and EPA
(20:5 n-3) - Omega-6 eicosanoids are pro-
inflammatory - Omega-3 eicosanoids are anti-
inflammatory** - It is important to maintain the
correct balance of n-6:n-3 fatty acids - Ideal is 4:1
- Average American 12-25:1
EPA and DHA
- EPA 20:5 n-3, most benefit for animals
- DHA 22:6 n-3
- Nutritionally desirable fatty acids
- Decreased heart disease, cancer, inflammatory diseases
- Critical in the brain (dry matter is 9% DHA) and retina (dry matter is
12% DHA) - Vital for fetal brain and eye development during pregnancy
EPA and DHA sources:
* Made by algae
* Fatty fish like salmon are rich in EPA and DHA
Omega-3 dats
- Plant oils contain the omega-3 fat alpha linolenic acid (ALA)
- Animals need other omega-3 fatty acids EPA and DHA
- Fatty fish like salmon are rich in EPA and DHA
- Chickens can convert ALA (from flax) to EPA and DHA and deposit the
fat in egg yolk
-feeding to food animals it can end up in the meat or eggs and be a source for people.
cats acid which they require
- Cats require Arachidonic
acid 20:4 n-6 - Not present in plant oils
- Another reason why vegan cat diets are
difficult
crude protein
- Measured using Kjeldahl reaction – a measurement of nitrogen
- Makes the assumption that all proteins are 16% Nitrogen or
- Nitrogen x 6.25 = protein, Not true all the time is an avg.
- Says nothing about the amino acid content of a diet
- Not all nitrogen measured with Kjeldahl is from amino acids-protein
- Non-protein nitrogen
- Allows for intentional or unintentional contamination of feeds e.g. melamine
essential AA
- Amino acids that can’t be synthesized animals or cannot be synthesized in
sufficient amounts to maximize production = Essential (EAA) - PVT TIM HALL
Phe, Val, Trp, Thr, Ile, Met, His, Arg, Leu, Lys
nonessential AA
- Amino acids that can be synthesized in amounts that meet their requirements to maximize production = Nonessential (NEAA)
ex: alanine, asparagine, glutamate
conditionally essential amino acids
-Essential in some species but not all
-Essential in some life stages
-Can partially replace the requirement for an essential amino acid
- Dietary requirement at certain stages of life
- Gly: required by broiler chickens in first 2-4 weeks after hatch
ex: cysteine, glutamine, glycine, taurine
Different animals have different essential
amino acid requirements
- Humans: don’t require histidine
- Cats: require glutamine and taurine (and high levels of methionine, arginine and leucine)
- Trout/salmon: require taurine
taurine
- Synthesized from Cys and indirectly Met
- Beta-sulfonic amino acid
- Often considered with the amino acids
- It is essential in cats/salmon, maybe in dog depends on what type of protein you are adding
-can only get from animal products
-not used in protein synthesis
taurine functions
-bile acid conjugation (dogs and cats conjugate all bile salts with taurine
-membranse stabization
-intercellular Ca levels (heart muscle)
-not present in plants
Taurine deficiency symptoms
- Retinal degeneration causing blindness
- Impaired reproduction and fetal development
- Hearing loss, impaired nervous function
- Feline dilated cardiomyopathy
amino acid sparing AA
- Cys and Tyr are conditionally essential because they can meet about 50% of the requirement for Met and Phe respectively
- Cys can replace ~50% of the Met requirement
- Tyr can replace ~ 50% of the requirement for Phe
- This means your requirement for Met is given as Met and Met + Cyt
met requirement in diet: 1:8
met + cys requirement in diet 4:1
Why not just feed Essential amino acids?
- To synthesize a non-essential amino acid you need 2 things:
- Carbon skeleton
- Amino group
- NEAA are the major source of amino groups for
synthesis of NEAAs - What happens if you don’t have enough NEAA in the diet? ADG decreases when you have less NEAA in diets, having max NEAA will maximize average daily gain.
lysine
- First limiting** amino acid in pigs
-only used in protein synthesis - Second limiting amino acid in poultry
- Low in grains: Animals raised on wheat/corn/barley diets must have supplements
- High in pulses soybean/pea
- High in canola meal
methionine
- First limiting amino acid in poultry
- Second limiting amino acid in pigs
- Can be spared by cysteine so usually give requirement as Met + Cys
- Low in legume-based diets; soybean meal
- Important in DNA metabolism
- Precursor of taurine
Threonine
- Can be deficient in animal diets
- Pulses are high in threonine; grains are low
- High levels in mucous lining of small intestine**
- Disproportionately high in endogenous losses**
- During mucosal diseases more mucous is produced; more Thr is required
Tryptophan
- 4th limiting amino acid in most diets
- Particularly low in corn
- The B-vitamin niacin can be synthesized from Trp
- Precursor for serotonin
- Important in brain, gut function and sleep
- Precursor for melatonin
- Controls circadian rhythms
Arginine
Needed in urea cycle to break down amino nitrogen
* Carnivores have a high requirement for Arg
* Cats and salmon
* Can’t produce enough arginine to upregulate urea cycle after a meal
protein digestion
Two objectives
* Digest dietary protein
* Reclaim digestive enzymes: they are protein too
- Endogenous protein is 30-50% of digesta protein
- If endogenous protein is lost in excess
- > Negative N balance even though dietary protein is adequate
endolytic enzymes
Trypsin
* Chymotrypsin
* Elastase
* Hydrolyze peptide bonds in
the middle of the protein
exolytic enzymes
- Carboxypeptidase A and B
- Amino peptidase
- Hydrolyze peptide bonds at
the carboxy or amino ends of
the protein
enzyme synergy
- Endolytic enzymes create more carboxy and amino ends
- Exolytic enzymes have more ends to work on
Absorption of Digestion Products (proteins)
- In jejunum, 2/3 AA are present as di and tripeptides; 1/3 as free AA
- Peptides and AA are absorbed by two processes: Diffusion and active transport
- Diffusion is important when the concentration of AA is high
- Active transport is efficient even at low conc. of AA
Active transport of AA
- Requires energy
- There a many different AA transporters
- Several amino acids may use the same transporter (ex. Lys and Arg
use System y+), AA transporters are very specific - Excess of Arg may restrict absorption of Lys by competition for AA transporter**
- Amino acid balance is important, excess of one can use all the transporters (compitition) and lead to deficiency in another
AA as energy substrate for the gut
The gut is 2-6% of body weight, needs energy and AA
- Responsible for:
10-20% of whole body CO2 production
50-75% of maintenance energy requirements**
-energetically expensive
examples:
glutamine–> 90% utilized by the gut in portal blood
glucose–> 8-15% utilized by the gut
the fate of absorbed AA
- Once absorbed into mucosal cells, most peptides are broken down by proteases to free AA
- Free AA are then transported across the mucosal membrane into the portal vein to liver
*once in liver Used for:
* Anabolism: protein synthesis
* Catabolism: excess AA are oxidized for energy
conditions for AA catabolism (normal, protein excess or starvation)
- Normal synthesis and degradation of cellular proteins:
- some amino acids released during protein breakdown are oxidized if not needed
for new protein synthesis - Dietary protein excess:
- When ingested amino acids exceed need in the body, the surplus is catabolized;
amino acids cannot be stored (protein has no storage form must be broken down) - Starvation or in diabetes mellitus:
- When carbohydrates are unavailable or not properly utilized, proteins are used
for fuel
Catabolism of AA Nitrogen in mammals leads to? what do we do to convert them?
- The amino groups produced by catabolism are extremely toxic
- They are converted into less toxic forms in mammals by the
following steps - Transamination (transfer amino group) HAS TO BECOME GLUTAMATE
- Oxidative Deamination (amino group removed)
- Ammonia transport to liver by GLUTAMINE
- Urea cycle (used up)
Transamination
-An amino acid has its amino group (N) removed and transferred to alpha-ketoglutarate
You end up with:
1) glutamate and
2) an alpha-ketoacid
This step requires energy*
Oxidative
Deamination
- Amino groups of most AA are
transferred to α-ketoglutarate - Release of this N as ammonia
is catalyzed by L-glutamate dehydrogenase - This regenerates α- ketoglutarate
-GLUTAMATE is the only AA that can be oxidativly demaninated
Ammonia Transport
- The free amino group is added
to a glutamate molecule giving
glutamine - This is transported to the liver by GLUTAMINE
urea cycle
- The amino group is released from the
glutamine reforming glutamate - The amino group is combined with CO2
- This enters the urea cycle and leads to urea
synthesis
why dont we just excrete ammonia?
- Ammonia is very toxic
- By keeping the amino group attached to amino acids, this toxicity is avoided
- Urea is relatively non-toxic and easy to excrete in a concentrated form
ammonia intoxication (toxosis)
- In ruminants, caused by the absorption of EXCESS AMMONIA from the rumen:
- Insufficient glucose to form α-ketoglutarate and therefore glutamine
- In cats LOW ARGININE diets can cause ammonia intoxication: Can be life threatening
- Symptoms are tremors, blurred vision, coma death
the fate of carbon skeletons
- Source of energy and glucose**
- Amino acids are either ketogenic or
glucogenic or both - Ketogenic amino acids form ketone
bodies:
-Acetone, acetoacetate or β-hydroxybutyrate - Can be used to synthesize fatty acids
- Glucogenic amino acids form glucose: Essential during starvation
protein deficiency in animals symptoms
- weight loss
- muscle loss & weakness
- poor digestion
- poor coat
- fluid build-up in chest or abdomen (serum protein decrease causes edema)
in humans called Kwashiorkor
protein energy costs
-protein is an inefficient as an E source
- Energy cost of:
- Protein metabolism
- Nitrogen excretion
- Heat increment
- Conversion of protein to fat
-high protein diets are poor for finishing animals: due to high cost of energy to convert energy substrates to fat
what determines Protein Quality
-Two things determine the nutritional quality of a protein:
* The amino acid content of the protein relative to the requirement of the animal (does it have the required mix of required AA in the right amount)
* The digestibility of the amino acids in protein (even if it has the right mix of AA if it isn’t digestible than it doesn’t matter)
where in the body is protein digested
- Feed proteins are digested in stomach and small intestine
- Absorption occurs in Small intestine*
- No absorption of AA in Large intestine:
- Undigested feed protein is digested by microbes in LI and turned into microbial
protein - Microbial protein is mainly excreted in feces
apparent fecal digestibility
- If amino acids found in feces are subtracted from AA in feed, the
apparently digested amount can be calculated - Example 10 g lysine ingested, 2 g lysine in feces
8 g absorbed
Apparent Fecal Digestibility is 80 %
AFD= 100% x (AA intake -AA feces)/ AA intake
microbial metabolism of AA
-bacteria in the gut can convert 1 AA to another
-Microbes in ceca and large intestine may change amino acids by
deamination and transamination
* Therefore, apparent fecal digestibility coefficients may be inaccurate
true digestibility
-considers microbe metabolism of AA
True digestibility =
100% x (Lysine ingested – (Lysine in feces + Lysine metabolized))/Lysine ingested
100% x (10 – (2 + 1))/10 = 70%
Note that the value for Lysine metabolized is positive if Lysine is destroyed
and negative if created
apparent Ilieal digestibility coefficient AID
AID= (AA intake - AA ileum)/ AA intake
Example: 10 g Lys ingested,
1.5 g Lys in ileal fluids
8.5 g Lys absorbed
AID coefficient is 0.85 OR 85% digestible
Endogenous Contributions to AA
- Amino acids are constantly lost from digestive enzymes, enterocytes,
bile, mucus, and other sources - These amino acids are secreted into the lumen of small intestine
- Some of them are not reabsorbed and end up in digesta captured at the
distal ileum - Taking them into account gives us True ileal digestibility
- Endogenous losses in a pig are measured by capturing the digestive
fluids at the distal ileum after a nitrogen free diet has been fed
True Ileal Digestibility Coefficient
- If AID is corrected for the endogenous losses, then a true ileal digestibility coefficient (TID) can be calculated
TID = AAintake-(AAileum –AAendogenous)/
AAintake
Digestibility measures and feed formulation
- Total amino acids in feed:
- Only if you don’t have any other information
- Try to do a digestibility trial before you formulate diets
- Apparent fecal digestibility:
- Not corrected for bacterial metabolism or endogenous losses
- Apparent ileal digestibility:
- Corrects for microbial metabolism (mostly)
- True ileal digestibility:
- Corrects for microbial metabolism and endogenous losses
AA Requirements of monogastrics
- Animals require amino acids-not protein
- Amino acids are building blocks for protein
- Lean meat mainly consist of H2O and protein
- We want as much lean meat deposited as possible
- Protein synthesis is an “all or nothing” event
- All AA need to be available at the same time
two things that determine protein quality
- The amino acid content of the protein relative to the requirement of the animal
- The digestibility of the amino acids in the protein
Protein Efficiency Ratio
PER = amount of wt gained/amount of protein consumed
-the higher the ratio the better
PER in animal nutrition
* Widely used in human and aquaculture nutrition
* Primitive method of assessing protein quality
* Not widely used in other agricultural species
Biological Value
BV = nitrogen retained/nitrogen absorbed*100
-Takes digestibility and amino acid balance into account
-A BV of 100 indicates complete utilization of a protein
-eggs and whey 100
the first limiting amino acid
- The First Limiting Amino Acid is the amino acid present at the lowest amount relative to the requirement
- The amount of this amino acid will determine the level of production
- Measure the requirement for every essential amino acid
- Formulate diets to meet these requirements
measuring AA requirements
- Animal growth studies generally used
- Requirement can be based on:
- Maximum gain
- Maximum feed efficiency
- Maximum yield of product eg. breast meat
- Three models are used
- Broken line model
- Quadratic model
- Exponential model
first rate limiting AA problems
- If we bring every amino acid up to its requirement in the diet, we will
maximize our profit-right? - Problems with concept:
- Takes account of deficiency but not excess
- Excess protein takes energy to metabolize
idea protein
- Is a perfect balance of amino acids that will cover the requirement of
the animals= No excesses, no deficiencies
Lysine is always set at 100 %
* All other amino acids are expressed as a percentage of lysine
* Allows for the calculation of the requirement of all amino acids if
lysine requirement is known
* Why is Lysine set to 100 in the Ideal Protein?
* Lysine has no metabolic function other than a component of protein
* Lysine is usually the first limiting amino acid
Advantages of Using Ideal Protein
- Balanced AA composition can be fed
- Over and under feeding of AA is avoided
- AA excretion in urine is minimized
- Maximum protein synthesis is supported
- Only need to know the requirement for Lysine
