AN SC 260 Ch. 3.2
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What are some alternate Nitrogen sources in mongastrics?
- - D amino acids, NPN (non protein nitrogen).
- - D isomer is poorly absorbed with the exception of D-methionine as it can be converted to the L form.
- - NPN can be used for synthesis of dispensible AA, but only limited amounts
Why are ruminants able to use D-amino acids and NPN effectively?
because of rumen microbes
What happens when there is excess intake of protein in monogastrics?
- – Decrease in food intake, weight gain
- – Reduction in fatty acid synthesis
- – Dull hair coat
- – Kidney and liver problems
What happens when there is excess protein in ruminants?
how do you judge the nutritively value of proteins?
Depends not only on dietary level and absorbability but also on metabolic usefulness
What is the maillard rxn?
glucose + amino = maillard group.
The maillard products actually cant be used in the body for amino acids. It just adds flavour
Reference to the nutritive value of proteins, what is a chemical score?
Compare AA profile to that of an "ideal" protein (egg albumen)
Reference to the nutritive value of proteins, what is a biological value?
- – Percentage of N absorbed which is available for body functions
- – Can increase BV of an ingredient by feeding with a complimentary protein
What is the protein efficeincy ratio? (PER)
– # of g of BW gain per unit of protein consumed
What is Net Protein Utilization (NPU)?
– Efficiency of growth of animals fed a test protein relative to animals fed a protein-free diet
Blood amino acid patterns?
– Feed increasing amount of a test amino acid, look for increase in blood
Amino Acid Oxidation?
– Use of amino acid for protein synthesis vs oxidation for energy
What is the biological Availability of AA
- varies from feedstuff to feedstuff.
- -Microbial assay
- -fecal/digesta analysis
- -growth assay
- -plasma AA
- -oxidation AA
These will all tell you how well the amino acid component meets the amino acid profile
What do microbes require in the rumen? And how much?
- Require nitrogen!
- -80% microbes can use NH3 as sole source of nitrogen
- -26% require ammonia absolutely
- -55% can use either amino acids or ammonia
What happens if there is an ammonia defeciency in the rumen? How does this happen?
This will lead to a decrease in microbial growth. This happens when there is a low intake of protein and NPN as well as a low degradation of protein in the rumen
What happens to most of the protein that enters the rumen?
It is hydrolozed to peptides, AA, then NH3, organic acids and CO2
How much protein esacpes degradation in the rumen? What is it called? Where is it broken down?
40% true protein on average. it is called by pass protein or RUP. Broken down in the abomasum to yield amino acids = dietary protein.
What is degradability?
rate and extent to which a feed protein is broken down in the rumen.
How much of the protein do the microbes in the rumen take? What do they do with it
they take 60% of the protein, make microbial protein which the body can use.
See figure on page 3
Do ruminants need extra bypass protien?
No, Most ruminants can meet protein needs from microbial synthesis + normal by pass protein.
Who needs extra by pass protein?
high producing animals such as rapidly growing young ruminants, peak lactation cows also require increased bypass protein
See page 4 Ammonia overflow picture
What is happening before ammonia overflow?
each increment in dietary CP results in a nearly equal increment in metabolizable CP
What is happening after ammonia overflow with respect to fish meal?
each increment in dietary CP results in a relatively large increment in metabolizable CP. However proportional increase is less than before ammonia overflow, there is high bypass protein, low degradation in rumen
What is happening after ammonia overflow with respect to high moisture haylege?
each increment in dietary CP results smaller incremements in metabolizable CP. There is lower by pass protein and greater degradation in the rumen.
What is happening after ammonia overflow with respect to NPN?
each increment in dietary CP results in no increment of metabolizable CP. There is no bypass protein.
What is happeing right before point of ammonia overflow?
rumen microbes capable of converting a high proportion of NH3 to microbial protein
What is happeing after point of ammonia overflow?
- - rumen microbes cant make more microbial protein
- - any increase in metabolizable protein comes directly from dietary protein
- -usually microbes get first shot at the nutrients
How do you increase the effeciency of protein use?
- -protein use is costly
- -use non protein nitrogen as a source of ammonia for rumen microbes
- -minimize the breakdown of dietary true protein
- -maximized by pass protein
- -combine NPN and protected protein
What is the goal of bypass protein
- - make it unavailable to rumen microbes
- - available for digestion in the abomasum and absorption in the small intestine
what are the methods of Bypass protein?
- - Naturally protected
- – Heat during normal processing
- – Heat and pressure treatment
- – Treatment with tannins
- – Treatment with aldehydes +/- heat
- – Ionophores
- – Lipid treatment
what is catabolism?
In protein metabolism refers to Degradation
What is anabolism?
In protein metabolism refers to synthesis
When are catabolism and anabolism happening?
Occur simulataneously. There is always protein being turned over
In reference to AA metabolism what happens at the SI
- - This is the first major site of AA metabolism
- - AA are important fuels for gut cells
- -Need glutamine, glutamate, and aspartate (100% catabolized in the gut)
- -Other AA (30-50% catabolized in the gut)
In reference to amino acid metabolism what happens at the liver?
- – Primary site of uptake of AA following a meal
- • ~20% used for synthesis of proteins and N- compounds
- – ~14% used in liver – ~6% released to plasma
- • ~57% catabolized in the liver
- • ~23% released into systemic circulation – Mainly branched-chain AA
- » Isoleucine, leucine, valine
Amino acid catabolism
- – AA (usually not stored only metabolized) not used for synthesis of proteins or N- containing compounds
- • Removal of α-amino group will be metabolized by the liver or kidneys will get rid of the nitrogen thru urine
- • Excretion of nitrogen
- • Oxidation of C-skeleton
What is the removal of an alpha amino group called?
- • Transamination
- – Transfer of amino group to α-ketoglutarate
- – Most amino acids
- - Amino acid + α-ketoglutarate ↔ α-keto acid + glutamate
What happens in the deamination of glutamate?
amino groups is removed from glutamate and moved onto a different group
How is nitrogen excreted in mammals?
- • Ammonium (NH4+) => NH3
- • Ammonia converted to urea by liver
- – Urea cycle
- » Urea secreted by liver into blood
- » Sequestered by kidneys for excretion in urine
How is NH3 (toxic) excreted from aquatic animals?
They have no shortage of water so expell by way of ammonia. Know as ammonotelic species.
How is NH3 (toxic) excreted in terrestrial vertebrates?
- » Ureotelic species
- » Urea less toxic, less water needed for excretion
How is NH3 (toxic) excreted in birds and reptiles?
- – very concentrated N waste
- » Uricotelic species
AA acid catabolism, oxidation of C skeleton? What does it produce? What do they do?
- • α–keto acids – α–keto acid + amino group <=> amino acid
- – Directly or via additional reactions feed into major metabolic pathways
- – Precursors of glucose (fuel for cells), fatty acids, ketone bodies (fuel some cells).
See diagram page 7 for overview of how animals excrete excess nitrogen.
AA acid catabolism, what is produced with the oxidation of the c skeleton? What is the function of these products?
- • Glucogenic amino acids
- – C-skeletons degraded to
- » Pyruvate or one of the 4- or 5-C intermediates of the Citric Acid Cycle
- – Major C source for gluconeogenesis when glucose levels are low
- – Catabolized for energy – Converted to glycogen or fatty acids
AA acid catabolism, what is produced with the oxidation of the c skeleton? What is the function of these products? K
- • Ketogenic amino acids – C-skeletons degraded to
- » Acetyl-CoA or acetoacetate
- – 2C units enter Citric Acid Cycle as Acetyl-CoA, 2 C lost as CO2
- » No net synthesis of glucose
- – Catabolized for energy – Converted to fatty acids or ketone bodies
- » No net synthesis of glucose
AA synthesis, what is transamination rxns?
• Amino group transferred from an existing amino acid to the α-carbon of an α-keto acid
AA synthesis, how are dispensible AA formed?
- • Synthesized from intermediates of major metabolic pathways
- – Amino acids arise from corresponding α–keto acid or derivatives
AA synthesis how are indispensible AA formed?
- - Tend to have more complex biosynthetic pathways than for dispensible amino acids
- • Animals lack/have limited biosynthetic capacity
- – May be lacking only a single enzyme
- – Unable to synthesize C-skeleton
Nutritional requirements for individual amino acids such as indespensible amino acids
- - cant make enough of em
- -cant even make them
Nutritional requirements for individual amino acids such as preformed amino acids
- • Dispensible amino acids
- – Transamination from an existing amino acid to a C- skeleton
See amino acid summary pic on page 9
Why dont cattle normally eat other animals?
- Dont need to...
- - lack stealth, claws, suitable detention
- - have requirements for fermentable carbohydrates and fibre
Why were cattle fed by products?
- -high quality protein source
- - amino acid- balance and availability
- -provided by pass protein
- -provided minerals
- - good use of byproducts
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