AN SC 260 - 3.2

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What are alternative N sources in monogastrics?

D-amino acids - poory absobed (except D-methionine), can serve as N source for AA if absorbed, converted to L form

Non-Protein Nitrogen - used for synthesis of dispensible AA, limited in monogastrics
What are alternative N sources in ruminants?

D-amino acids and Non-Protein Nitrogen - can be used effectively by ruminants (rumen miocrobes)
What is an example of excessive protein intake in monogastrics?

16, 32, 48% in pigs

As CP intake increases, food intake, weight gain, FA synthesis, hair coat quality, and kidney/liver health decreases
What is an example of excessive protein intake in ruminants?

Ammonia toxicity
What does the nutritive value of proteins depend on?
- Dietary level
- Absorbability
- Metabolic usefulness
Why are Maillard products great? What are they not so great?

Flavour

AA cannot be used
What is a chemical score?

Comparison of an AA profile to that of an "ideal" protein
What is the "ideal" protein?

Albumen
What is a biological value (BV)?

% of N absorbed which is available to for body functions
What is protein efficiency 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
What are blood AA patterns?

Correlation btwn increasing amount of test AA in feed and increase of that AA in blood
What is AA oxidation?

Use of AA for protein synth vs oxidation
How can the biological availability of AA be measured?
- Microbiological assay
- Fecal/digesta analysis
- Growth assay
- Plasma AA
- Oxidation of AA
Rumen microbes require nitrogen. Where do they typically get it from?

Ammonia NH3
What does ammonia deficiency in the rumen do?
- Decreases microbial growth
- Low intake of protein and NPN
- Low degredation of protein in rumen
What is bypass protein?

Protein that escapes rumen digestion (still travels through the rumen but is not degraded)

~ 40% of true protein is bypass protein
Where is bypass protein digested?

Abomasum to yield AAs
In what situations is matching protein and energy sources in ruminants important?
High producing animals
- Rapidly growing young ruminants
- Peak lactation cows
What has happened when ammonia overflow is reached?

Microbes have reached capacity of converting NH3 to microbial protein

Any increase in metabolizable E from this point on comes directly from dietary protein = bypass protein
How do you increase the efficiency of protein use?
Make protein unavailable to microbes
- Combine NPN and protected protein
- NPN is a cheap source of NH3 for rumen microbes
- Microbes break down NPN instead of true protein = increased bypass protein
Heat treat
What are some ways to protect protein from microbial degradation?
Treat with:
- Heat
- Heat and pressue
- Tannins
- Aldehydes +/- heat
- Ionophores
- Lipid
What are the 2 forms of protein metabolism?
- Catabolism - degradation
- Anabolism - synthesis
What role does the intestine play in AA metabolism
- First major site of AA metabolism
- Catabolizes 100% of glutamine, glutamate, and aspartate
What role does the liver play in AA metabolism?

Primary site of AA uptake following a meal
What are 3 methods of AA catabolism? Why is the AA acid being catabolized?
- Removal of alpha-amino group
- Excretion of N
- Oxidation of C-skeleton
AA not used for synth of proteins or N-containing cmpds
What are 2 ways an alpha-amino group can be removed?
- Transamination
- AA + alpha-keoglutarate <--> alpha-keto acid + glutamate
- Deamination
- Glutamate - NH3 is removed, O from a H2O molecule forms double bond in place of NH3 and regenerates alpha-ketoglutamate
What are 3 types of C-skeleton oxidation?
- Alpha-keto acids
- alpha-keto acid + amino group <=> amino acid
- Glucogenic AA
- C-skeletons degraded to pyruvate or 4-/5-C intermediate in Citric Acid Cycle
- (major source of gluconeogenesis)
- Ketogenic AA
- C-skeletons degraded to Acetyl-CoA or acetoacetate
How are AAs synthesized?
- Transamination reactions
- Amino group removed from existing AA and transferred to an alpha-keto acid
- amino acid A + alpha-keto acid <--> alpha-keto acid + amino acid B
Summarize AA metabolism