Amino Acid requirements Flashcards
What are old methods used to determine amino acid requirements?
-crude protein
-biological value
-protein efficiency ratio
What are new methods used to determine amino acid requirements?
-AA requirements
-ideal protein balance
Crude protein (used until 1970s)
Nutrient requirements of pigs and poultry were given as % crude protein
eg. 10-20kg pigs need 18% crude protein
-based in typical corn-soy diets
Protein efficiency ratio
Amount of weight gained/amount of protein consumed
**higher the ratio, better it is
Higher protein efficiency ratio foods/protein
High=canola protein, egg whites
What does Protein efficiency ratio assess?
Protein quality
-used in human and aquaculture nutrition
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
Biological values for some common proteins
First limiting amino acid
The amino acid present at the lowest amount relative to the requirement
*will determine the level of production
How do you incorporate the first limiting amino acid concept?
- Measure the requirement for every essential amino acid
- Formulate diets to meet these requirements
How do you measure amino acid requirements?
Animal growth studies; based on:
-maximum gain
-maximum feed efficiency
-maximum yield of product (eg.breast meat)
Example for determining amino acid requirements (eg. Lysine)
- give a basal diet that meets requirements for all nutrients EXCEPT lysine
- Add Lysine-HCl to the basal diet to give different levels of lysine and see where you get maximum gain, feed efficiency, or product yield
What models are used to measure amino acid requirements?
-broken line model
-quadratic model
-exponential model
Broken line model
Issues with broken line model
-doesn’t always fit data
-often feeding aa over requirement causes a decrease in growth so no real plateau
Quadratic model
-better for situations where feeding aa over the requirement causes a decrease in growth
Can you just bring every amino acid to its requirement in a diet to reach max profit?
Not necessarily
-takes into account the deficiency but not the excess
-excess protein takes energy to metabolize
What is ideal protein?
The perfect balance of amino acids that covers the requirement of the animals
*WITH NO EXCESSES AND NO DEFICIENCIES; therefore max production and profit
How do you get ideal protein?
Set lysine to 100%, and then all other amino acids are expressed as a percent of lysine
Why is lysine set to 100 in 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 avoided
-AA excretion in urine minimized
-max protein synthesis is supported
-only need to know the requirement for lysine
How does ideal protein change with age?
The maintenance requirement increases relative to requirement for lean deposition as pigs age
*certain AA needs will increase with age eg. Met+Cys
Does ideal protein change with maintenance and growth?
Yes, certain AAs will have higher requirements depending on growing stage
eg. Met+Cys needed at a higher amount for maintenance
