12 – AA Requirements

Question 1

What are 2 things that determine the nutritional quality of a protein?

Answer 1

1. AA content of the protein relative to the requirement of the animal
2. Digestibility of AA in the protein

Question 2

What new methods are used for determining the nutritional quality of a protein?

Answer 2

• AA requirements
• Ideal protein

Question 3

What is the equation for protein efficiency ratio?

Answer 3

• PER=amount of weight gained DIVIDED by amount of protein consumed
• *if lower=need to feed more to get enough protein
• Animal proteins: egg white=3.71, minced beef=3.36
• Plant proteins: canola protein=3.29, soy protein=1.60

Question 4

PER in animal nutrition

Answer 4

• Widely used in human and aquaculture nutrition
• Primitive method of assessing protein quality
• *NOT widely used in agricultural species

Question 5

What is the biological value (BV) equation?

Answer 5

• BV=nitrogen retained DIVIDED BY nitrogen absorbed MULTIPLE by 100
• *takes digestibility and AA balance into account
• If BV=100, it indicates complete utilization of a protein
• Ex. whey and egg=100, milk=93

Question 6

What is the first limiting AA?

Answer 6

• AA present at the lowest amount relative to the requirement
• *amount of this AA will determine the level of production
• Need to measure the requirement for every essential AA and formulate a diet to meet the requirements

Question 7

What can AA requirement be based?

Answer 7

• Maximum gain
• Maximum feed efficiency
• Maximum yield of product (Ex. breast meat)

Question 8

Example: determining the requirement for Lysine

Answer 8

• Provide a basal diet that is adequate for all nutrients other than Lysine
• Then you can add Lys-HCl to give different levels of Lys
• Get an AA titration study/graph
  o Then do math

Question 9

What are the 3 models used to measure the requirements of AA?

Answer 9

• Broken line model
• Quadratic model
• Exponential model

Question 10

Broken line model

Answer 10

• Get a linear response and then a plateau phase
• *requirement=where the linear response and plateau phase MEET
• Doesn’t always fit data well
• Often feeding AA OVER requirement causes a decrease in growth (so is no real plateau)
  o Quadratic model would fit better for this situation

Question 11

Quadratic model

Answer 11

• Goes up and then goes down
• Produce an equation that describes the line AND find the point of maximum weight gain (the highest point)
• *more precise then broken line method

Question 12

If we bring every AA up to requirement in the diet, would maximize profit?

Answer 12

• NOT necessarily
  o Takes account deficiency but not excess
  o Excess protein takes energy to metabolize
• *ideal protein=balance of AA (all at 100%, NO more, NO less)

Question 13

How does ideal protein work?

Answer 13

• Lys is always set at 100%
• All other AA are expressed as a percentage of Lys
• *allows for calculation of the requirement of all AA if Lys requirement is known

Question 14

Why is Lys set to 100 in Ideal Protein?

Answer 14

• Lys has NO metabolic function other than a component of protein
• Lys is usually the first limiting AA

Question 15

What are the advantages of using ideal protein?

Answer 15

• Balanced AA composition can be fed
• Over and under feeding of AA is avoided
• AA excretion in urine is minimized
• Maximum protein synthesis is support
• Only need to know the requirement for Lysine

Question 16

Ideal protein and age

Answer 16

• Maintenance requirement INCREASES relative to requirement for lean deposition as pigs grow older
• *ideal protein changes as pig grows old
• *differences in maintenance and growth