Flashcards in Animal Nutrition Test 4 Deck (296):
% molecular weight of atoms in protein
S and P: less than 1%
Range of MW of proteins
5,000- many millions
Average molecular weight of proteins
How many AAs naturally occur in nature?
How many AAs are commonly found in proteins and are required by the body?
How many major biochemical reactions and supportive reactions and ATP are needed to make a peptide bond?
20 major biochemical reactions
Hundreds of supportive reactions
Principal dry matter constituent of body organs?
When is the dietary requirement for protein highest? Lowest?
Highest in young growing animals (have to maintain all tissue AND make new tissue), lowest at maturity
2 things that determine the composition and function of a protein
Arrangement of AAs and length of chain
2 types of protein
Simple (yield a-AAs or their derivatives on hydrolysis) and conjugated (protein + nonprotein prosthetic group)
2 types of simple proteins
Globular and fibrous
Features of globular simple proteins
Smaller than fibrous proteins
Made of a compactly folded peptide chain(s)
Features of fibrous simple proteins
Insoluble animal proteins
Made of extended or cooked peptide chains
Very resistant to proteolytic enzymatic digestion (remember bc fiber is indigestible)
Other names for fibrous simple proteins
Scleroproteins or albuminoids
3 examples of fibrous simple proteins
Collagen, elastin, and keratin
3 examples of prosthetic groups on conjugated protein
Phosphoric acid, carb, or nucleic acid
Examples of conjugated proteins
Nucleoproteins, glycoproteins, mucoproteins, lipoproteins, chromoproteins, metalloproteins, and phosphoproteins
3 functions of animal cell membrane proteins
Transport things between inside and outside of cell
Supports for catalytic functions
(Probably other important but less defined functions)
It is a lipoprotein that makes a sheath around nerve fibers
3 things that make up erythrocyte membranes
Mucolipids, phospholipids, and loosely bound proteins
Where to sugars attach to protein to make a glycoprotein?
Sugars are accepted by amino acid residues in the polypeptide chain
Function of chondroitin sulfate
It's complexed with protein in cartilage, tendon, and skin so portably serves connective tissue purposes
3 types: A, B, and C
6 mucoproteins that were mentioned
Mucoproteins in mucous secretions (abundant)
Mucoproteins of submaxillary gland secretions
Another name of essential amino acids
Indispensable amino acids
List of essential AAs
MATT HILL VP (remember it includes: Arg, Thr, **TRP**, Phe)
This list was made for rats during the mid 20th century but we still use it
Methionine can be partially replaced by:
Phenylalanine can be partially replaced by
Proline is a dietary essential for
This means that the essential amino acids can vary with species! Also with production; genetics, age, environment, and sex
4 amino acids that are likely to be deficient in farm diets for monogastrics
Lys (usually the first limiting AA)
(To remember: the lice tripped three times and met their match)
Nonessential amino acids
These are all metabolically essential but are made by the animal so they don't need to be in diet
Weird ones: citrulline and hydroxyproline
Plus all the rest of the 20 amino acids that aren't essential except glutamine and asparagine (probably because the acid version of these are on the nonessential list)
Is arginine required in the diet of all species for maximum growth?
No, most adults don't need Arg except for cats and dogs.
When mature cats and dogs don't get Arg in their diet, what deficiency symptoms arise?
Hyperammonemia, tremors, and high levels of urinary orotic acid
Citrullene can replace which amino acid in the diet of the cat and some other species?
Why should Gln be put on the essential amino acid list?
Needed to support the metabolic requirements of the intestinal mucosa during illness
May be important in normal GI tract immune function
May be important in normal metabolism of the pancreas and liver
Cats and sulfur-containing AAs?
Cats have a high sulfur AA requirement
Only species that requires taurine (a B-amino sulfonic acid that's not in protein but occurs as a free AA in diet). When they don't eat it their retinas degenerate
In which species do adults need dietary His?
Is amino acid balance important to the ruminant? If not, what is?
No, amount of N and readily available carbs
What is the nearly perfect protein for meeting animal needs? Why?
Albumin in eggs
It has an ideal AA composition and it's easy to digest
The balance among the AAs in the protein
Nutritive value is variable bc no 2 proteins have an identical AA composition
Where are most body proteins found?
Skin, hair, and hooves
8 Specialized functions of proteins in the body
Enzyme catalyzed reactions
Hormone mediated effects
Immune function (protection)
Storage and transport of nutrients and O2
Categories of tissue proteins
Metabolically active peptides and polypeptides
Why is cooked meat from older animals often tough?
Because collagen content increases with aging of the animal. So old animals have lots of collagen and collagen is known to shrink when heated bc of its high Pro and Hyp content
How is elastin different from collagen?
Elastin resembles denatured collagen
Elastin consists of long, randomly ordered polypeptide chains
Elastin breaks more easily than collagen
They are both insoluble in water and resistant to digestive enzymes
Often found associated with collagen
Lots of collagen in muscle, only a little of elastin
More than 20 enzymes found in sarcoplasm involved in muscle metabolism
Where is keratin found? Why is it of little value as a protein supplement?
hair, wool, feathers, hooves, horns, claws, and beak
It's resistant to acid, base, heat, and digestive enzymes so obviously you can't use it as a supplement
What are the major blood proteins and where are they made?
Albumin and a series of globulin (a,B,y)
Apoproteins A, B, and E
They're mostly made in the liver
Enzymes are also called:
Major jobs of enzymes
Degradation metabolic reactions
How many enzymes are found in animal cells?
Net protein accretion
The balance between protein synthesis or degredation
How much energy is needed to keep the net protein accretion balance?
15-22% of total energy expenditure
Some examples of important protein hormones
Active vs passive immunity
Active= actually come in contact with antigen (pathogen) and body makes antibodies
Passive= get antibodies against antigen without exposure to actual antigen. Usually comes from mother to baby
Vaccines can be either!
Infectious particles with no nucleic acids that are made of an abnormal form of a normal cellular protein
Diseases caused by prions
Mad cow (BSE)
Chronic wasting disease
Other prion diseases are known to occur in mink, cats, and humans
Which body tissues are prions found in?
Brain and other nervous tissue
Why have slaughter house meat byproducts been banned from the diets of ruminants?
Because consumption of feed products containing nervous tissue from prion-infected animals can transmit the prions to the ruminant
4 steps in the conversion of dietary protein to tissue protein
1) intact dietary protein hydrolysis in GI tract
2) amino acids in intestinal lumen absorption from GI tract
3) amino acids in blood synthesis in tissues
4) now we have intact tissue proteins
Where do proteolytic enzymes come from?
Epithelial cells lining the GI tract lumen
2 factors that determine nutritive value of dietary value?
Hydrolysis efficiency (which determines the degree of absorption of individual amino acids)
Balance of absorbable essential amino acids
Proteins can be characterized nutritionally on the basis of...
Degree of utilization of the AAs after absorption
These are also the 3 factors affecting the degree of utilization of feed proteins
What is digestible protein?
Protein that disappears from the ingesta as it passes down the GI tract
Apparent protein digestibility
(I-F)/I ( where I= N intake, F= N in feces)
DOESNT MEASURE QUALITY, JUST QUANTITY
Problem: F includes metabolic N too (that from metabolic processes, cell turnover, and enzymes)
Where does metabolic fecal N come from?
Normal metabolism of tissue protein
When is the only time that whole proteins are absorbed across intestinal epithelium? How?
Postnatal (first 24 hours), pinocytosis
Usually proteins have to be hydrolyzed to AAs to be absorbed, but antibodies in the colostrum of the mom can be absorbed whole by pinocytosis
AAs are absorbed from the gut by:
Why can lots of one AA increase the requirement for another AA?
They compete with each other for transport
3 main sources of the amino acids in the digestive tract
Recycled with other N and returned to the lumen
Made by microbes
What raw ingredients do microbes need for amino acid manufacture?
Ammonia, sulfur, and a carbon source
They can make all amino acids with these things
What tissues are capable of making the nonessential AAs?
Lactating mammary gland
What do microbes degrade AAs to?
Ammonia, S, fatty acids (acetate, propionate, butyrate, and branched chain fatty acids), and CO2
Where in the body are AAs degraded?
Liver is the principle organ degrading all AAs except branched chain amino acids (BCAA) and Gln.
Degradation of many essential and nonessential AAs also occurs extensively in small intestinal cells
Are AAs made from recycled N of any consequence to animals?
Yes, a high proportion of intestinal mucosal cell AA supply for enterocyte growth and maintenance is derived from endogenously supplied AAs rather than those absorbed directly from the lumen of the intestine
Why is feeding excessive protein to a ruminant a bad idea?
It results in ammonia release, which is absorbed and wasted as urea lost in the urine
A low protein diet can be supplemented by microbial protein derived from endogenous recycling of urea
Where does the protein found in the lower gut of the ruminant come from?
Protein that escaped fermentation in the rumen and microbes that washed out from the rumen
What does the rumen escape of protein depend on?
Type of protein
Rate of degradation (this depends on whether it's soluble and moves with liquid or insoluble and moves with particles)
What does the concentration of RUP depend on?
The dietary protein concentration and level of intake
3 major things that happen to amino acids after absorption?
-Tissue protein synthesis (AAs move into the cell and are used for protein synthesis within 5-10 minutes after absorption from the gut)
-Synthesis of enzymes, hormones, and other metabolites (these participate in digestion, metabolism, immunity, heredity, and endocrine synthesis)
-Deamination or transamination and use of the carbon skeleton for energy
Each organ or tissue in the body has its own rate of protein ____
Constant turnover of protein in body and all cells require protein which is why there's a protein maintenance requirement
What do polypeptide growth factors (PGF) do in the body?
They influence protein metabolism and animal development and maintenance (at the cell, tissue, and organ levels)
Not well understood though
Transfer of an amino group from one amino acid to the carbon skeleton of a keto acid
MAKING AMINO ACIDS BY DEGRADING ANOTHER ONE
Removal of an amino group and lone H from the carbon skeleton to make ammonia (NH3), which then enters the urea (ornithine) cycle. The carbon skeleton enters the TCA and is used to make ATP.
DEGRADING AMINO ACID NOT MAKING THEM
Where do the AA for body protein synthesis come from?
Absorption by GI tract or synthesis by transamination in tissues
Basis for classifying AA as essential or nonessential? How do we know?
The carbon skeleton
If it's an essential AA, the animal can't make the carbon skeleton
We know this because several of the 10 essential amino acids can be replaced by their corresponding a-hydroxy or a-ketoanalogs
How is it that some dietary nonessential AAs can replace some of the need for dietary essential AAs?
Essential AAs can make some of the nonessential AAs!
Ex: Cys is made from Met and can replace about half of the dietary Met
Describe the urea cycle using x+y+2=Q+B=urea
Ammonia+CO2+ATP=carbamyl phosphate + ornithine = urea
Ammonia comes from deamination, just use P from ATP, and urea should really be citrulline, which then undergoes a series of reactions to make urea
Where does the urea cycle take place?
Liver and to a lesser degree enterocytes
Same places that degrade amino acids! This makes sense because deamination is part of degradation
Cost of protein supplements?
Expensive, so we try to get all absorbed dietary AAs into proteins to save $$, but this is a tricky process because many factors come together to turn dietary AAs into animal protein
Nonessential amino acids comprise what percent of tissue protein?
3 major reactions to make the nonessential AAs
3 requirements for protein synthesis
Nucleic acids (made by cells)
How fast is protein synthesis? Use hemoglobin as an example
Fast. Hemoglobin is 146 AAs long and is made in 1.5 minutes
Amount of amino acids in the diet
No diet has exactly the right amount of AAs, usually we feed excess bc it's cheaper than buying expensive protein supplements or using crystalline AAs to perfectly balance an animals diet for AAs.
Not a problem bc usually excess AAs can be deamination and used for energy or transaminated to make another AA
Is protein a metabolic requirement?
Why do nonruminant omnivores have stricter AA requirements than some nonruminat herbivores?
Bc some nonruminant herbivores can use NPN to make AAs in the lower digestive tract
Can adult ruminants live with no protein at all in the diet?
Yes, they can use the protein made by the microbes from NPN and also from the microbes themselves
Why is protein deficiency so common?
Most energy sources are low in protein (not a lot of protein in plants) and protein supplements are expensive
Factors that influence protein requirements
Growth increases requirements
Sex (males usually need more than females)
Genetic makeup within species
Why is protein:calorie important in the diet?
Even if the animal eats a lot of protein, it can still be made protein deficient if it's fed a high calorie diet (lots of fat). This happens because animals only eat to satisfy energy requirements, so they'll eat less of the high calorie feed and consequently eat less protein --> protein deficiency
we have little ability to balance protein intake with requirements
When will the body use protein for energy?
When it's provided in excess of the metabolic requirement
When calorie intake is insufficient
Signs of protein deficiency
Reduced growth rate
Reduced or negative N balance
Reduced efficiency of feed utilization
Reduced serum protein concentration
Edema (in severe cases)
Reduced birth weight of young
Reduced milk production
Reduced synthesis of certain enzymes and hormones
AA deficiency usually causes these same symptoms, but there are some symptoms associated with certain AA deficiencies
What happens to other AAs if one is deficient?
Deamination of the remaining amino acids (which results in loss of the ammonia as urea and use of the carbon chain for energy)
This is a big waste of good AAs!
Trp deficiency causes:
Thr or Met deficiency causes:
Lys deficiency in birds causes:
How has recombinant DNA technology changed the way we balance rations for their AA needs?
We've used recombinant DNA technology to make microbes mass produce certain AAs. We can now use these in feed (before, Trp, Thr, and other AAs were only available for $$$$$). Now we can use lower protein diets to provide adequate protein and AAs for growth and other productive functions.
Ideal protein diet
Formulate AA mixtures that exactly match the AA requirement of the animal in a given state of growth and with a particular genotype
What is kwashiorkor?
It's protein deficiency in young human children who are weaned from their mothers milk when the next child comes along
Translates to "first-second", and is a problem in 3rd world countries bc their food doesn't have a lot of protein in it
Symptoms of kwashiorkor
Decrease in blood protein, which causes bloated bellies and thin limbs
The better the _____________ the better the protein
Amino acid balance (this goes along with nutritive value)
Also, the closer the dietary protein to the proportions required by the animal, the better the protein will be used by the body for the manufacture of new protein
Example of AA that is toxic when fed at high levels
Note: you can also feed too much protein!
Which isomer of amino acid is the natural one used most by the body?
Can D isomers of AAs be used by animals?
Yes, the D isomers of some essential AAs can be used for growth by most animals. Some D AAs can be converted to the L form by D-AA oxidase and transaminase
Can alpha-keto acids be used by animals? How?
Yes, they can form the corresponding L amino acid by transamination
Coprophagy vs cecotrophy
Coprophagy= the animal eats its poop bc it's suffering a dietary deficiency of protein (also some vitamins). Ex: horse
Cecotrophy= organized eating of poop directly from the anus with the intent of taking advantage of cecal fermentation. They don't just eat any feces but rather those referred to as cecotrophs.
Beyond cecotrophy, there's no reason to feed NPN to a nonruminant (also NPN can be toxic in small quantities to them)
What are proteins degraded to in the rumen?
Peptides and AAs, most of which are further degraded to ammonia, organic acids, and CO2
What happens to ammonia released when microbes digest feed protein or NPN?
It's either removed from the rumen by absorption (at a basic pH) and much of it is recycled back to the rumen as urea via the blood and saliva
...or used by the microbes along with carbs to make protein
Biological value (BV)
The % of N absorbed from the gut that is available for productive use by the body
Can also think of it as a measure of the relationship of N retention to N absorption
A perfect protein would have a BV of 100% (MEASURE OF QUALITY)
Good tool for evaluating a feed protein bc the degree of utilization of a feed protein depends not only on its absorbability, but also on its utilization after absorption
BV of rumen microbes
Good NPN sources for ruminant?
Feed-grade urea and biuret
These can be used by the microbes and can often be very cost effective ration components
Many feeds have naturally high levels of protected protein. Put these in order of decreasing % of bypass protein:
Extruded whole soybeans
Distillers dried grain
Corn gluten meal
Corn gluten meal & distillers dried grain
Corn grain & extruded whole soybeans
Do ruminants have a dietary AA requirement?
No, NPN can be the primary N source in a ruminant ration, and ruminants can survive and produce if the only N they get is NPN
Why would it be good to feed some good quality protein to a ruminant even though they don't require it?
High producing dairy cows and rapidly growing calves and lambs need higher quality AAs than microbes make to meet their full production potential (ruminants can't produce maximally when only fed NPN). Also, microbes can't make enough limiting AAs to maximally produce muscle protein and milk. Therefore you would use protected high quality protein in this situation
Do rumen bacteria require ammonia?
Many require it but not all. However, most rumen bacteria utilize ammonia.
Some ways of creating protected feed protein?
Chemical derivatization (such as by formaldehyde treatment)
Use of inhibitors of microbial amino acid deamination
Examples of NPN compounds other than urea
What does efficient NPN use depend on?
Solubility of the NPN
Availability to the microbes of readily available carbs (to make protein)
How can milk production be improved in a dairy cow fed only NPN?
Supplement with Met, Lys, and other AAs to augment milk production
Amino acid antagonism
Growth depression that can be overcome with supplementation with an AA that is structurally similar to the antagonist
Amino acid imbalance
Any change in the proportion of dietary AAs that has an adverse effect preventable by a relatively small amount of the most limiting amino acid(s)
Same as antagonism but the supplemented AA must be the one that's limiting
Amino acid toxicity
When the adverse effect of an excess AA can't be overcome by supplementation with another AA
2 diseases caused by excess AAs that caused us to study the effects of excess AAs?
Phenylketonuria (don't have enzyme to metabolize Phe properly)
Tryrosinemia II (don't have tyrosine aminotransferase)
Have to give special diets low in these AAs to treat
Effects of excess AA consumption
Slight suppression of food intake followed by a return to normal intake
How does strenuous exercise affect dietary protein requirement?
It increases efficiency of protein metabolism (decrease dietary protein requirement)
Effects of feeding excess protein
Bad because of ammonia toxicity, which can have negative effects in energy metabolism (perhaps by inhibiting TCA)
Define protein quality
The measure of the ability of a protein to supply the essential AAs in the proper quantity and ratio needed by an animal for maintenance and production
A high quality protein supplies essential AAs in the ratio and quantity needed to make all proteins in the body
True digestibility of a protein
Where M is metabolic N (problem: it's very difficult to measure this!!!)
basically the same thing as apparent digestibility but you take the metabolic N out of the fecal N
(We consider proteins with a BV of ____ or higher capable of supporting growth)
Formula for BV
[I -(F+U)]/(I-F) all times 100
Where U is urinary N
Same as apparent digestibility but add U to F and take away F from I on the denominator
On the whole, do animal proteins or plant proteins have better BV?
Complementary effect for BV
Proteins with poor BV can be mixed with other proteins to give a higher BV for the animal
Give the BV of the following:
Egg: 95% (yolk 100%, white 83%)
Legume seed: 70%
Legume leaf: 65%
Egg is the natural protein that has the best BV!
Net protein value (NPV)
BV*the digestive coefficient
Takes into account differences in digestibility between proteins, so it's a better measure than BV
Net protein utilization (NPU)
[(total body N on test protein)-(total body N on protein free diet)]/total N intake
This measures efficiency of growth by comparing body N resulting from feeding a test protein with that resulting from feeding a comparable group of animals a protein-free diet for the same length of time
Feeding a pure AA can improve the NPU of a protein source
Advantage of NPU
Lots of values can be obtained over a brief test period with a minimum of measurements
Protein efficiency ratio (PER)
Weight gain/protein consumed
Determined by conducting a feeding trial, measure both values in grams
Which is the best measure of protein utilization under ALL conditions?
There isn't one
Advantages of PER
Simple and only needs minimum facilities and analytic work because only weight gain and protein consumed in a particular time period of 2-3 weeks are needed
How many chemicals and enzymes are needed for digestion of dietary proteins?
1 chemical (HCl in the stomach)
Several enzymes (pepsin in the stomach, rennin in the stomach of young animals, proteolytic enzymes secreted by enterocytes, and pancreatic enzymes)
Breaks down proteins into polypeptides by cleaving at aromatic AAs (remember HCl denatures the protein first)
Secreted by gastric mucosa as pepsinogen, but activated by HCl to pepsin at pH 2
Rennin is activated by:
Pancreas secretes trypsinogen, which is activated to trypsin by enterokinase (secreted by small intestine mucosa)
Optimum pH of Trypsin?
Where does trypsin cleaves polypeptides?
Lys and Arg
Chymotrypsinogen A, B, and C are secreted from the pancreas and activated by trypsin to chymotrypsin
Where does chymotrypsin cleave the polypeptide?
Tyr, Trp, and Phe
Elastogen (pancreatopeptidase) is secreted by the pancreas and activated to elastase by trypsin
Optimum pH of elastase
Where does elastase cleave polypeptides?
Val, Leu, Ser, Ala
Carboxypeptidase A and B
Carboxypeptidogen A and B are secreted from the pancreas and activated to carboxypeptidase by trypsin
Where do carboxypeptidase A and B cleave the polypeptide?
Both cleave off single AAs from the carboxyl end (COOH) so they're called exopeptidases
Optimum pH of carboxypeptidase A and B
Where does aminopeptidase in the brush border of the small intestine cleave the polypeptide?
It cleaves single AAs from the N end
What does dipeptidase in the brush border of the small intestine cleave off the polypeptide?
It cleaves dipeptides
Does fermentation of protein occur in the large intestine?
Yes, microbes ferment protein from sloughed mucosal cells and proteins not digested earlier
If it's NPN, it's incorporated into microbial protein that causes problems in interpreting digestion trials bc we can't distinguish one protein from another
How do feedstuffs vary in their protein content from one to another?
Most commonly used feeds contain at least some proteins but the quality and quantity (either can be limiting for growth an production) can vary from very good to very poor
What 2 things to you need to know in order to properly feed protein?
1) the minimum protein needs for the animal
2) the specific AA requirements for the animal
Therefore, you need to combine individual proteins with individual AAs to provide both quantity and quality of protein for the animal's needs
2 kinds of measurement units for protein in common ration balancing technique are:
Amount per animal per day (g, kg, lb)
% of the diet
How much protein in plant stems?
Very little, and it's poorly digested
How much protein is in plant leaves?
Leaf has most of the protein we find in forages. Therefore, as leaf:stem ratio goes down, so does the protein content
Percent crude protein in:
Cereal grains: 8-14% CP
Which has more CP, oilseeds or oilseed meal?
Cereal grains (corn, wheat, milo) are low in what 2 things?
Examples of oilseeds
Percent CP in oilseeds? Are they good or bad Lys sources?
Good Lys source
Examples of oilseed meal
Percent CP in oilseed meals? Are they good or bad Lys sources?
30-50% (makes sense bc meals have more CP and oilseeds alone are only 20-50%)
Good Lys source
Percent CP in animal proteins? Are they good or bad Lys sources?
VERY good Lys source
Examples of animal proteins
Rendering products (tankage, meat meal, and blood meal)
Percent CP in milling byproducts? Are they good or bad Lys sources?
Variable CP, moderate in Lys
These are products left over after preparing grains for human consumption
Percent CP in these milling byproducts:
Corn gluten meal
Corn gluten meal: 40-60% CP
Corn bran: 12-16%
Wheat bran: 15-17%
Percent CP in forages? Are they good or bad Lys sources?
Low in Lys (except alfalfa)
Percent CP in these forages:
Early growth wheat pasture
Prairie hay: 5-7%
Early growth wheat pasture: 30%
What is the most common commercial source of NPN? What does it look like?
Urea, white/brownish powder or crystal
Urea is ___% nitrogen
However, feed grade urea has a few impurities so it's average N is 45%
The average N content of AAs is __% by weight
% N of any feed multiplied by ____ equals CP
Urea example: 45%N * 6.25 = 281% CP (this looks weird but it's right bc urea has a crude protein EQUIVALENT of 281%, so a little urea will go a long way in a ration)
Maillard (browning) reactions
When AAs have extra amino groups that can react with reducing sugars (especially in the presence of acid or heat) to make an indigestible, brown colored AA-sugar complex
Which AA is especially susceptible to browning?
Lys (this is bad bc Lys is usually the first limiting AA)
How do you measure the degree of heat damage?
By measuring ADF-N. high values mean low protein availability
Circumstances under which browning can occur?
1) hay is too wet when put up, so it heats up and browning can occur
2) material gets too hot (100-120 degrees F) during silage making, maybe bc of poor packaging or dry material being ensiled, causing browning
Browned feeds have what kind of odor? Are they eaten well by livestock?
Sweet tobacco, yes
How can you use browning for a positive outcome?
You can experimentally cause browning reactions with xylose in the presence of heat as a means of increasing bypass protein
Difference between true protein and urea
True protein can be used by everyone
Urea can only be used practically by the ruminant and nonruminant herbivore (they have microbes with urease that can release ammonia from it to make microbial protein, which can only be used by these 2 types of animals)
Define bioenergetics. Why is it important to nutrition?
Energy and it's metabolism BY ANIMALS. It's important bc energy is the most important item in an animal's diet and all animal feeding standards are based on energy needs
More energy info available on ruminants or monogastrics?
Ruminants, probably bc they have a more complicated digestive system?
Why is the study of energy so different from the study of the macromolecules?
Energy isn't tangible like macromolecules, and it can be derived from almost all organic compounds eaten by the animal
How does an animal derive energy for itself?
By partial or complete oxidation of organic molecules. These are absorbed from the diet or from metabolism of tissues (primarily fat or protein and, to a lesser extent, carbs)
Significance of ATP in body energy transfer?
Energy transfer from one chemical reaction to another occurs primarily by means of high energy bonds (ATP)
Energy transfer examples:
Chemical to heat (oxidation of fat, glucose, or AAs)
Chemical to mechanical (muscle activity)
Chemical to electrical (brain, glucose oxidation)
All animal functions and biochemical processes require ____
Energy, to drive the various processes to completion
Is precise measurement of energy transformations in animal function an easy thing to measure?
Yes for some reactions, but no for excretion and digestion bc they have an energy input from so many different tissues and chemical reactions that it's difficult to evaluate their cost to the animal
Potential to do work (work=Fd)
This broad definition isn't applicable to animals bc were usually more concerned with the utilization of chemical energy
Amount of heat required to raise the temp of 1 g of water from 14.5 to 15.5 degrees C.
1 cal = ____ J
1 Kcal = ___ cal
1 Mcal = ____ Kcal
Gross energy (GE)
The amount of heat resulting from the complete oxidation of food, feed, or other substances as fuel
Also called heat of combustion (chemical term)
What device measures GE?
Oxygen bomb calorimeter
Typical gross energy value for:
Why the difference?
Carbs: 4.1 Kcal/g
Protein: 5.65 Kcal/g
Fats: 9.45 Kcal/g
The differences in these energy contents comes from the state of oxidation (as the C:H ratio and the O and N content goes up, energy goes down). Fats have less oxygen per carbon than carbs do, so fats requires more oxygen for oxidation and gives off more heat in the process
Why is GE worthless if used independently as a measure of feedstuff energy value?
Poor quality material (oat straw) has about the same GE value as high quality feed (corn grain) so this is useless
Why is it more reasonable to use GE values for humans than for livestock?
Quality isn't as important to humans bc we don't eat a lot of indigestible material, so we put our caloric value of foods as GE
Define apparent digestible energy (DE)
Intake of food energy - energy lost in feces
How do you arrive at a figure for DE?
The IE of an animal is carefully measured over a period of time accompanied by collection of fecal excretion for a representative period of time. Both are analyzed for energy content then you calculate DE
What is the single largest loss of ingested nutrients from the body?
Energy lost in the feces
3 reasons apparent DE isn't a true measurement of the digestibility of a given diet?
1) GI tract excretes things that end up in the feces
2)GI sloughed cells end up in forces
3) in some species, undigested microbes and their metabolic byproducts may constitute a large portion of the feces
How is true DE determined?
In addition, you measure the energy in fecal excretions (metabolic fecal energy) of an animal that is fasting or being fed a diet presumed to be completely absorbed (milk or eggs) or fed intravenously. The amount of excretion is then subtracted from the total fecal excretion of the fed animal
What happens to the % of fecal energy as a dairy cow is fed increasing amount of hay?
What happens to heat losses as level of feed is increased?
Formula for total digestible nutrients (TDN)?
You carry out a digestion trial and sum up digestible protein (DCP), carbs (NFE and crude fiber) and 2.25 times the digestible ether extract (crude fat, DEF)
What is TDN used for?
It measures energy for ruminants and swine in the US
What is TDN comparable to? How do you convert it to that?
DE, except its expressed in units of weight or %, whereas DE is in units of energy (in Kcal, remember: IE-FE)
2000 Kcal of DE for every lb of TDN (DE=TDN*2000)
Is TDN a good measure of energy to use in formulating rations?
No, bc literature TDN values are old, most were done with sheep that were fed at lower levels than normal, the values were computed with the difference method (which can have an associative effect), feed composition has changed due to crop improvement and fertilization practices, now there's improved or different analytical data, and many labs now do analyses on detergent fiber rather than crude fiber
Define Metabolizable energy (ME)
ME= DE-(urinary energy + gaseous digestion products)
To calculate, do: (9.6DE - 0.202protein%)/100
In ruminants, there's a simpler formula but it's not that accurate bc the ME:DE ratio can change as the diet and level of feed change: ME=DE*0.82
What animal is ME commonly used for? Why?
Poultry, they excrete their feces and urine together (it's tedious and time consuming to make complete urine collections and do energy values on urine)
What percent of consumed energy may be lost as methane in a ruminant?
8% of GE at maintenance and 6-7% at higher levels of feed.
Low quality diets result in more or less methane?
How stable are urinary energy losses?
If ME is the most descriptive and reproducible measurement of feeds, then why don't we have actual values for all feeds?
Few labs have the facilities and budget to collect and analyze respiratory gases and urine
What is NE?
NE= ME- (HF+HI)
HI is the heat increment (heat of nutrient metabolism)
HF is the heat of fermentation from the rumen, cecum, and large intestine
Net energy is the added heat production in the fed animal as compared to the fasting animal, or the portion of feed available to the animal for either production or maintenance!!
How has NE changed over time?
It's getting better. Even though some of the NE values are derived rather than gathered experimentally, they are still better than other methods. Hopefully we can move the various ruminant industries more towards NE as time goes by. Comparing NE to TDN would be like comparing the space shuttle to a horse and buggy
2 major categories that NE is used for by the animal?
Maintenance and various productive purposes
Also called specific dynamic effect when referring to a specific nutrient
= heat production associated with nutrient digestion and metabolism over and above that produced prior to food ingestion
Sources of HI?
The heat is produced by oxidative reactions that are...
1) not coupled with energy transfer mechanisms (high energy bonds), or the result of incomplete transfer of energy, and are...
2) partly due to heat production resulting from work of excretion by the kidneys and to increased muscular activity of the GI tract, respiratory, and circulatory systems resulting from nutrient metabolism
Where does most of the HI originate? What organ?
+80% originates in the viscera (organs). Metabolism in the liver accounts for most of the HI
If most of a feed is absorbed and deposited in tissues, what happens to HI?
It is very low (it's deposited in tissues so it's not metabolized)
How do nutrient deficient diets influence HI?
They increase it (lots of fiber that's being metabolized?)
How do frequency of feeding and feed intake affect HI?
Increasing both of these results in higher HI
Why is HI not the same as total body heat production?
Because the body will produce heat regardless of whether the animal is eating
How accurate are our estimates of HF?
Not accurate, HF is poorly quantified bc different sources get different values
HI vs HF in a cold environment
Both can be useful to warm the body just as well as controlled metabolism of nutrients (thermogenesis)
HI vs HF in a hot environment
HI is detrimental, requiring additional energy expenditures to dissipate it
What happens in ruminants when urea is fed instead of protein?
It reduces heat production
What happens to a ruminant's HI when minimal protein is fed?
Heat production decreases
How do fat feeding and reduced fiber feeding affect HI?
Increasing fat and reducing fiber both lower HI, so these are helpful in hot climates
Factors that affect heat production (loss) in animals?
Is heat production highly correlated to body weight?
Name some ways an animal can change its surface area
It may change with environmental temperature when the animal stretches out, fluffs up its feathers, or otherwise changes its posture
What is metabolic weight (metabolic size)?
BW^a fractional power (we use 0.75 for heat production)
BW= body weight
Used to measure heat production
When heat production is expressed on the basis of surface area, how does it help?
The BW^0.75 is much more uniform
Can we accurately and precisely measure and predict energy metabolism?
No, it may be similar in widely diverse animals, but it's not identical and may be altered by many different factors
The condition in which a minimal amount of energy is expended to sustain the body
This provides comparative base values where energy requirements are not confounded by other factors
What are the conditions under which basal metabolism must be measured?
The animal should be in a postabsorptive state (so HI and HF don't add to the body heat production, will be indicated by very low methane production), a state of muscular repose but not asleep, and in a thermoneutral environment
What is 25% of an animal's energy needs required for?
Circulation, respiration, secretion, and muscle tonus
Things that can reduce an animal's energy expenditure?
Prolonged fasting or starvation
What happens to basal metabolism as we age? Why?
It increases to 1 year old then decreases throughout the rest of life. This may be related to differential development of tissues that have different oxygen requirements
How do these neuroendocrine factors affect basal metabolism?
Nervousness and hyperactivity:
Sex: males have higher metabolism
Castration: lowers metabolism
Hypothyroidism: lowers metabolism
Nervousness and hyperactivity: raises metabolism
Hormonal changes: causes seasonal changes in basal energy needs
Give an example of how basal metabolism varies with each species and breed
Sheep have higher metabolism than cows
Bos indicus cattle appear to have fasting HP and maintenance requirements that are about 10% less than those of Bos Taurus
How do these affect basal metabolism?
Fasting: decreases it
Muscular training: increases it
Thinking: slightly increases it
When a nonproductive animal neither gains nor loses body reserves
Rarely of interest in modern agriculture bc were usually trying to make our animals produce, but it would be of interest in pets
It's been very difficult to put precise estimates on maintenance requirements of animals under different environmental conditions
What are factors that we must consider to establish an animal's maintenance needs?
Needs for basal metabolism
Energy losses during nutrient metabolism
Increased activity during normal functions like grazing
Environmental factors that may alter energy needs
How much of ME goes to maintaining the body of beef cattle?
What is the energy of maintenance used for?
To carry out various functions that tissues and organs perform for the benefit of the entire organism, including circulation and respiration, as well as liver, kidney, and nervous function
Factors that may cause maintenance energy needs to vary?
Breed or species
The authors of the text suggest that, in cattle, the NE of maintenance values given for various feedstuffs probably overestimate the relative value as compared to NE of gain. What do they offer to support his opinion?
The maintenance estimates were estimated by the comparative slaughter technique, and these values seem to be too low as compared to calorimetric experiments on cattle
How do animals dissipate heat?
Evaporation, radiation, convection, and conduction
Within the thermoneutral zone, what affect does temperature have on an animal's body temperature?
Within the thermoneutral zone, heat production is essentially INDEPENDENT of temperature and is determined by normal animal metabolism, feed intake, and efficiency of energy use
What is the primary regulator of body temperature within the thermoneutral zone?
Regulation of heat dissipation
What happens when the effective ambient temp increases above the animal's thermoneutral zone? What happens to productivity and energy requirements?
The animal promotes heat loss by evaporation from the skin (sweating) and from the lungs by increased respiration rate (panting)
Productivity decreases bc of reduced feed intake
Energy requirements increase bc elevated body temperature results in increased tissue metabolic rate and increased work of dissipating heat
What happens when the effective ambient temperature decreases below the thermoneutral zone?
HE (heat production) produced from normal tissue metabolism and fermentation is inadequate to maintain body heat. As a result, animal metabolism must increase to provide adequate heat to maintain body temperature (this increase is called cold thermogenesis)
What is summit metabolism and how long can it be maintained?
Maximal attainable heat production, only a few hours
What factors affect heat production?
Adaptive changes (either behavioral or physiological) in response to changing climate
Can animals better protect themselves from hot or cold temperatures?
Heat stress to the point where the animal can't dissipate all the heat can occur at mild temperatures if the animal is adapted to cold and is consuming large amount of food. High humidity reduces rates of evaporative cooling and makes heat stress even worse
How is efficiency a concern to producers?
Efficiency is vital to profitable production
What is the common means of expressing feed efficiency?
Units of production/units of feed required
Ex: 4 lbs of gain per 2 lbs of feed
Why is it unfair to compare the efficiency of a feed in producing products on a DE basis if one feed is hay and the other is a concentrate?
Roughage is gonna be much lower in available energy than a concentrate, so the comparison is poor in terms of utilization of available energy (DE, ME, or NE)
Why is it so difficult to measure efficiency of body weight gain or loss?
The energy content of body gain may vary widely
Rank the efficiencies of body functions on their caloric efficiency:
Growth and fattening
From highest caloric efficiency to lowest:
Growth and fattening
Maintenance may be so efficient bc of the more efficient utilization of the HI and HF in maintaining body temp
Less efficient use of energy for production as compared to maintenance is due in part to a decline in digestibility of a given diet as feed intake increases, particularly in ruminants
How efficient is early postnatal growth?
Quite efficient (it approaches that of maintenance)
Is fat or protein deposition more efficiently done? Why?
Protein, probably bc of its dynamic state and more rapid rate of turnover in the body than is the case for lipid tissues
Is it often economically feasible to feed animals for max intake and rate of production? Why?
Yes, maintenance requirements represent a small percentage of dietary intake for young animals, thin animals, and any animals fed appreciably less than maximum intake
Net efficiency and Gross efficiency
Net efficiency =Caloric value of the product/caloric intake above maintenance. It is less affected by level of intake and more affected by the genetic capability of the animal
Gross efficiency= caloric value of the product/caloric intake. It's affected by level of production and age
Which is the most efficient producer of food energy and which is the least? Why such a large difference?
Most efficient: milk
Least efficient: beef
Bc beef cows produce at a very low level compared to a dairy cow, thus, maintenance is a much greater proportion of total feed intake, and gross efficiency drops considerably
What is the net result in gross and net efficiency with higher rates of feeding in the ruminant?
They both improve (eat more often it improves your metabolism)
Affect of increasing feed consumption on digestibility in nonruminants?
Generally less depression of digestibility takes place as feed consumption increases in nonruminants
Is ME or DE more affected by intake?
How do monensin and lasalocid affect efficiency? Why?
They're antibiotic feed additives that generally result in reduced feed consumption with little, if any, effect on daily gain. (More efficient so don't have to eat as much)
This happens bc of an increased production in the rumen of propionic acid (used more efficiently than other VFAs) and a reduction in methane production without having any appreciable effect on digestibility
If I'm using DE or TDN values, what species am I likely working with?
Swine or horses
What energy values are likely to be available for sheep and goats?
DE, TDN, or ME
Why can't we be too precise in calculating feed values or animal requirements?
Variation in feed ingredients, among other factors
NEg and NEm
NEg = net energy required for weight gain
NEm = net energy required for maintenance (assumed to be 77Kcal*BW^0.75)
Are pregnancy needs and milk production expressed as NEm or NEg?
NEm bc they are used with similar efficiency as maintenance
To estimate total required NEm, take the sum of
Milk + maintenance + pregnancy
5 components of NEm
Waste formation and excretion
NEm leads to heat production!!