Growth Flashcards
What must newborns do after birth?
Make a number of major adaptations since many things were being taken care of by their mother.
ex. temperature regulation (newborns have a lower TNZ)
What is brown adipose tissue?
Brown adipose tissue (BAT) is tissue that helps keep newborns warm.
It is comprised of many fat droplets with abundant mitochondria that can oxidize their own fatty acids and synthesize ATP.
BAT is effective at converting nutrients to heat, and is stimulated by the sympathetic nervous system.
ex. pigs need heating lamps because they do not have BAT
It was originally thought that levels of BAT decreased as an animal ages, but now it is thought that some may be associated with deep muscle tissue.
Describe the ETC
NADH passes e- through a series of proteins to oxygen
This pumps H+ into the intermembrane space
H+ flows back into the matrix through ATP synthase, turning the enzyme and making ATP
Describe the relationship between TCA cycle and heat production
When TCA increases, heat production increases (use of ATP)
When TCA decreases, heat production decreases
Describe BAT and uncoupling protein 1
Uncoupling protein 1 in BAT allows H+ to flow back into the mitochondrial matrix without making ATP.
This is called non-shivering thermogenesis
H+ does not flow through ATP synthase, and the TCA continues to run and generate heat
How is carb metabolism modified for a newborn animal?
Dietary source of carbs is lactose
Gluconeogenesis is needed
Liver glycogen is mobilized immediately after birth (it beaks before birth)
How is lipid metabolism modified for a newborn animal?
Blood free fatty acids increases rapidly from fat cells after birth
Milk fat becomes an important dietary source of lipids
Body fat deposition accelerates in the neonatal period
How is protein metabolism modified in a newborn animal
Rapid rates of lean growth and tissue protein synthesis
Milk protein is high in essential amino acids (EAA), which have high biological value
Early growth has the fastest and highest rate of protein synthesis
Describe the generic trend in an animals growth
Rapid growth in early life that slows over time
What is composition of gain affected by?
Age, breed, genetics, and gender
Energy and protein intake (homeorhesis and nutrient prioritization)
Muscle grows rapidly first, bone grows steadily, fat grows slowly then increases
Describe the composition of proteins
Proteins are nitrogenous compounds of nutritional importance
- all proteins contain nitrogen
- true proteins are chains of amino acids (AA)
- non-protein N includes ammonia and urea, they are not AA or true proteins (NPN can be utilized by rumen microbes to make protein)
What roles do proteins play in the body
Proteins are the principal component of organs and lean tissue
They have a great functional diversity:
- cell membrane structure
- mechanical support
- nutrient transport
- enzymes
- hormones
- antibodies
Describe protein levels on a fat free basis
Proteins are constant or consistent in the body on a fat free basis
Where are the majority of the body’s proteins found?
Body fluids
it is available for breakdown if an animal is not eating enough protein; muscle can also be broken down but this is not ideal
What affects a protein’s deposition in a day?
The difference between protein synthesized and protein degraded. (futile cycle)
Why do proteins and AA have high turnover rates?
The high turnover rate enables a change in protein composition and ensures that proteins are functional. Constant turnover also allows adaptation.
Turned over AA are recycled and 75-80% are reutilized for new protein synthesis. The remaining 20-25% have their amino groups removed, their C skeletons are metabolized, and the ammonia is detoxified.
Over time, proteins can misfold or breakdown, so they must be replaced; high turnover ensures replacement
Proteins needed by the animal now can be made and they can then be broken down later for future proteins
What are the steps of protein synthesis?
expression of mRNA for the protein, and then synthesis of the protein on a ribosome
What determines the protein a cell utilizes?
The gene that is transcribed
Describe the relationship between increasing protein yield and protein requirement of an animal.
The amount of protein made by an animal is regulated by their cells. If an animal’s protein requirement is met, the only way to increase its protein yield would be to enhance the genes that code for it.
The animal will not make more protein if they’re deficient and you feed them more protein.
If an animal is at its protein requirement, it will not make more protein if you fed it more protein; this relates to the broken stick model, the system cannot be pushed
Describe the rate of protein synthesis in the body including specific locations
The rates of protein synthesis varies in different tissues and is high in the liver because the number of enzymes made there and in the gut because of rapid cell loss/turnover.
Rate of protein synthesis is lower in muscles than in the gut or liver.
What does net protein synthesis depend on?
Rate of synthesis vs. rate of degredation
Where is protein synthesis the most efficient?
Milk and egg production
It is less efficient in meat production because there is an associated cost of maintaining muscle protein after it is made
How can changes in protein deposition be made?
By different combinations of changes in synthesis and degredation
What are some general properties of amino acids?
- contain 15-18% nitrogen
- have primary, secondary, tertiary, and quaternary structures
- 20-25 AA are found in common dietary protein
- they are chemically diverse, but have a common general formula
- mostly water soluble
all amino acids contain an amino group, and central carbon atom, a carboxyl group, and a defining side chain (often labeled “R”)
Describe AA as isomers
AA are optically active (except for glycine); 2 optical isomers
L (levo-rotational)
D (dextro-rotational)
Discuss L-isomer AA
The L isomer is the form found in plants and animals; i.e. the L isomer is the naturally occurring form of AA
Discuss D-isomer AA
The D isomer is a form of AA that are chemically synthesized
What does the nutritional value of the D-Amino Acid depend on?
This depends on the AA
The D-form is converted to the L-form by deamination and re-amination; they must be able to be transaminated
What is the significance of D-form AA?
Deficient amino acids can be synthesized (as D-form) and added to a feed, where they are converted to the L-form in the body
What are the two most supplemented AA?
Methionine and lysine because they are commonly deficient
What is transamination?
The transfer of the amino group of one AA to the C-skeleton of a keto acid
This is equivalent to AA synthesis
How are AA classified?
A. By chemical structure
Major groups are:
- neutral
- acidic
- basic
- sulfur-containing
- aromatic
- heterocyclic
B. By metabolism
- glucogenic or ketogenic
C. By essential and nonessential
- (aka disposable or nondisposable)
What does it mean if an AA is glucogenic?
This means these AA can serve as precursors in gluconeogenesis (can be converted to pyruvate) for glucose formation
What does it mean if an AA is ketogenic?
This means that these AA are broken down to acetyl-coA, a precursor for ketone bodies
What is the difference between essential and nonessential AA?
Essential amino acids cannot be synthesized by the animal and must be supplemented in the diet. Nonessential amino acids can be synthesized by the animal with the proper starting materials.
What is deamination?
The removal of the amino group from the C-skeleton of an AA
This allows for the amino group to enter the urea cycle and for the C-skeleton to be metabolized
Where are AA broken down?
The liver
What are some functions of the liver?
- breaks down AA
- synthesizes many proteins including serum albumin
- supplies AA to the circulation when needed
What is the urea cycle and what does it do?
The urea cycle detoxifies ammonia
Ammonia gets put in with energy, and urea is the result
Produces urea from ammonia
Occurs in the liver of mammals
General equation:
NH3 + CO2 + 3ATP –> urea (NH2)2CO
Why do birds and reptiles not have a urea cycle?
Birds and reptiles convert N to uric acid instead of urea. Uric acid is fairly insoluble and non-toxic, which is desirable for the embryo while in the egg since it cannot urinate.
Uric acid is excreted in feces as a dry mass.
This minimizes water in the bladder and minimizes water loss as a whole, which is an important adaptation in dry environments where these species have metabolic water as their main source and cannot afford to lose it.
When is AA catabolism increased?
When:
- dietary protein intake exceeds requirements
- composition of absorbed AA is unbalanced (ex. one or more AA is limiting)
- Gluconeogenesis from AA is increased (ex. fasted animal or low carb diet; only glucogenic AA can be used (carnivores use protein to make glucose))
Discuss biosynthesis of AA
Nonessential AA make up 40-50% of tissue protein
Not all must be synthesized because the diet will provide most of them
If nonessential AA are in short supply, the body will make up the deficit (with transamination, needs an amino N) provided that an adequate supply of amino N, C skeletons, and energy are available
i.e. nonessential amino acids can be made in the body via transamination
What are the essential amino acids?
Phenylalanine
Valine
Threonine
Methionine
Arginine
Tryptophan
Histidine
Isoleucine
Leucine
Lysine
PVT MAT HILL or PVT TIM HALL
What do optimal rates of tissue protein synthesis require?
- adequate total quantity of AA
- mixture of AA that matches the composition of the proteins being synthesized
The dietary protein requirement is really an amino acid requirement for tissues
Discuss the poor quality and higher quality proteins in relation to the broken stick model.
For higher quality proteins with an ideal AA balance, less protein has to be fed before the stick “breaks” and protein deposition no longer changes
For proteins with a poor AA balance, more protein has to be fed to meet the maximum response because it has fewer essential AA
This is problematic because protein is expensive, and increased urea production from excess protein intake can cause pollution
What is biological value?
Biological value of a protein is the ability of a specific dietary protein to supply AA in the relative amounts required for protein synthesis by body tissues
BV is mainly influenced by essential amino acid composition
BV = N intake - (fecal N + urinary N) / N intake - fecal N
BV = retained/absorbed
How does biological value of a protein vary?
BV is not fixed, but varies with the varying needs of different species and physiological and nutritional states
BV also varies between proteins and what they are being used for (ex. growing animals have different AA requirements, so BV will differ; animal protein has a higher BV than plant proteins, etc.)
Discuss ideal proteins
Ideal proteins will have all essential AA at or over 100% of the requirement level
Discuss poor proteins
Poor proteins do not have all essential AA at or over 100% of the requirement level
Discuss the effect of having a limiting AA in a diet
An animal can only grow as fast as the limiting AA
Discuss the water barrel analogy
Water held in a barrel is proportional to capacity to allow for protein synthesis; there is no substitution for AA if they are essential
What is the goal regarding protein in ruminants?
The goal is to feed them a diet that maximize the production of protein by rumen microbial populations since they have a high AA profile
What is a complementary feed?
Feeds with AA that match each other’s deficiencies
Discuss protein breakdown and absorption
Dietary proteins must be digested to small peptides and AA before they can be absorbed
This is a two step process that begins in the stomach and ends in the small intestine
Protein is broken down by pepsin (stomach) and trypsin and chymotrypsin (pancreas) into peptides. The peptides are broken down to small peptides, and peptidase (pancreas and small intestine) break peptides down to AA
How does absorption of peptides and AA occur
This process relies on transporters
There are transport systems in the enterocytes of the small intestine (ex. for di and tri peptides, or specific AA based on side chain qualities)
Peptide transport requires no energy (passive transport), but some amino acids transport does require energy (active transport)
AA can be transported out of the cell and into the body by these transporters
What is AA antagonism?
Growth depression from an excess of one AA that can be reversed by adding a second AA.
Unlike an imbalance, the supplemental AA does not have to be limiting
What is AA toxicity?
Growth depression from an excess of one AA that cannot be reversed by adding a second AA
What is an AA imbalance?
Deficit of one or several AA that can cause depression in growth or production and can be reversed by addition of small amounts of AA
What are the consequences of low dietary protein?
reduced growth rate, increased fat, low milk or egg production, poor feed efficiency
What are the consequences of severe protein deficiency?
reduced growth rate, weight loss, scruffy hair and other standard deficiency signs
What are the consequences of excess dietary protein?
high feed costs, normal growth, enlarged kidneys, excess water intake, increase in pollution
What are the consequences of adequate AA pattern but low energy in the diet?
reduced growth because AA are degraded and used as an E source
Discuss excess dietary protein
- Has an energetic cost to the animal
- synthesis of urea
- contributes to N pollution in water
- leaching into ground and runoff
into surface water
- leaching into ground and runoff
-contribution to ammonia emission
- urease in feces creates ammonia
when mixed
- can contribute to infertility (especially in ruminants)
- expensive
The majority of ammonia emissions in the U.S. comes from livestock
