Concepts in Amino Acid Nutrition for Growing Pigs

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Concepts in Amino Acid Nutrition for Growing Pigs

• Dr. Hans H. Stein
• Swine Nutritionist
• South Dakota State University

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Concepts in amino acid nutrition for growing pigs

• 1. Introduction
• 2. The requirement for amino acids
• 3. The first limiting amino acid
• 4. The ideal protein
• 5. Digestibility of amino acids

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1. Introduction

• Amino acids are building blocks for protein
• Lean meat mainly consist of H2O and protein
• We want as much lean meat deposited as possible
• Protein synthesis is an all or nothing event
• All AA need to be available at the same time

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1. Introduction, cont.

• Genetics determine the pigs capacity for lean
  meat deposition
• Nutrition determines if the genetic capacity is
  utilized
• Different genetics have different requirements
  for amino acids

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2. Amino Acid Requirements
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2.1 Amino Acid Requirements

• The amino acid requirement is the sum of the
  requirement for maintenance and for production
• In a growing pig, the maintenance- requirement is
  very low
• Therefore, the requirement is mainly determined
  by the requirement for production (lean
  deposition)

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2.2 Lean Deposition Curve
Gram LEAN Deposited/day
125 kg
5 kg
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2.3 Amino Acid Requirements- total daily intake
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2.4 Amino Acid Requirements- as of diet
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2.5 Practical Diet Formulation

• Because of the changing lysine requirement,
  several diets are usually fed during the growing
  period
• Historically, 3-4 diets were used
• Now, 7-10 diets are commonly used
• makes it easier to feed according to requirement

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2.6 Phase Feeding
LYSINE
280 lbs
10 lbs
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3. The First Limiting Amino Acid
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3.1 The Purpose of Protein Synthesis

• Proteins are synthesized for
• maintenance
• enzymes, hormones, hair, skin, etc
• production
• lean meat, milk, fetal growth, etc.

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3.2 Proteins have a short life
Protein
Degradation
Synthesis
Amino Acids
There is a constant synthesis and degradation of
the proteins in the body
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3.3 Amino Acids Available for Protein
Synthesis

• Dietary Amino Acids
• Amino Acids from degraded body proteins

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3.4 Protein Synthesis

• Takes place in the cytosol of cells
• The amino acid sequence is pre-determined via the
  genetic code
• All amino acids need to be available at the same
  time
• Protein synthesis is an all or nothing process

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3.5 Example of a Protein

• CYS-TYR-ILE-GLN-ASN-CYS-PRO-LEU-GLY

The sequence of amino acids in a protein is
always the same
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3.6 The concept of the First Limiting
Amino Acid

• The First Limiting Amino Acid is the amino acid
  present at the lowest amount relative to the
  requirement
• The amount of this amino acid will determine the
  level of production

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3.7 The First Limiting Amino Acid
of requirement
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3.8 Lysine is often the First Limiting Amino
Acid

• In corn-soybean meal-based diets for pigs and
  poultry, lysine is usually the first limiting
  amino acid followed by tryptophan, threonine, and
  methionine

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4. Ideal Protein
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4.1 Ideal Protein

• Is a balance of amino acids that will cover the
  requirement of the animals
• Lysine is always set at 100 , - all other amino
  acids are expressed as a percentage of lysine
• Allows for the calculation of the requirement of
  all amino acids if lysine requirement is known.

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4.2 Ideal Protein, example.

• IP Ex.1 Ex.2
• Lysine 100 1.1 1.2
• Methionine 30 0.33 0.36
• Threonine 65 0.72 0.78
• Tryptophan 17 0.19 0.23
• Valine 68 0.75 0.82
• Isoleucine 60 0.66 0.72
• Leucine 100 1.1 1.2
• Phenylalanine 50 0.55 0.60

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4.3 Advantages of Using Ideal Protein

• Balanced AA composition can be fed
• Over-and underfeeding with AA are avoided
• AA excretion in Urine is minimized
• Maximum protein synthesis is supported
• Only need to know the requirement for lysine

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4.4 IP for Maintenance and Lean Deposition

• Lean Depos. Maint.
• Lysine 100 100
• MetCys 57 120
• Threonine 59 152
• Tryptophan 17 26
• Valine 68 70
• Isoleucine 58 82
• Leucine 101 72
• Phenylalanine 50 54
• Histidine 32 32

Baker,1997
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4.5 Ideal Protein changes with age

• Maintenance req. increases relative to req. for
  lean deposition as the pigs grows older
• Therefore, the ideal protein changes as pig grows
  older

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4.6 Ideal Protein for diff. weights

• Weight 10-20kg 20-50kg 50-110 kg
• Lysine 100 100 100
• MetCys 60 62 64
• Threonine 65 67 70
• Tryptophan 17 18 19
• Valine 68 68 68
• Isoleucine 60 60 60
• Leucine 100 100 100
• PheTyr 95 95 95

Baker, 1997
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5. Digestibility of Amino Acids
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5.1 Review

• Feed proteins are digested in stomach and small
  intestine
• Absorption occurs in SI
• No absorption of AA in LI
• Undigested feed protein is digested by microbes
  in LI and turned into microbial protein
• Microbial protein is mainly excreted in feces

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5.1 Review, cont.

• Not all AA present in a feed protein are absorbed
  prior to the distal ileum
• The percentage of AA that are absorbed in the SI
  differ between feed ingredients
• Therefore, diet formulations based on total
  levels of AA are inaccurate

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5.2 Absorption vs. Digestibility

• Absorption is a concept that can be defined but
  not easily measured
• Digestibility can be measured
• It is assumed that amino acids that are digested
  are also absorbed

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5.3 GI-tract of The Pig
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5.4 Fecal Digestibility

• If amino acids found in feces are subtracted from
  AA in feed, the apparently digested amount can be
  calculated
• EX 10 g lysin ingested, 2 g lysin in feces
• 8 g absorbed
• Fecal Digestibility is 80

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5.5 Microbial Manipulation

• Microbes in LI may change amino acids by
  deamination and transamination
• Therefore, fecal digestibility coefficients may
  be inaccurate
• EX 10 g Lys. ingested, 1 g eaten by microbes,
  2 g found in feces.
• Our calculated digestibility was 80, - but in
  reality, only 70 was absorbed by the pig

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5.6 Bypassing the Microbes

• Because of the microbial manipulation, fecal
  digestibility coefficients are not used any
  longer
• To avoid the influence of the microbes, digestive
  fluids are captured at the distal ileum
• Digestibility coefficients are calculated based
  on the disappearance of amino acids prior to the
  distal ileum

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5.7 Intestinal Cannula
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5.8 Intestinal Cannula
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5.9 Collection of intestinal fluids
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5.10 Calculating Ileal Digestibility Coefficients

• EX 10 g lys ingested, 1.5 g lys in ileal fluids,
  8.5 g lys absorbed
• Digestibility coefficient is 85

Digestibility coefficients calculated this way
are called ileal digestibility coefficients
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5.11 Endogenous Contributions

• Amino acids are constantly lost from enterocytes,
  bile, mucus, and other sources
• These amino acids are secreted into the lumen of
  SI
• Most of them are digested and reabsorbed
• Some of them are not reabsorbed and end up in
  digesta captured at the distal ileum

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5.12 Endogenous Amino Acids
Endogenous Amino Acids
Dietary AA
End of Ilium
Small Intestine
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5.13 Measuring Endogenous Losses

• Endogenous losses in a pig are measured by
  capturing the digestive fluids at the distal
  ileum after a nitrogen free diet has been fed

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5.14 Influence of Endogenous AA

• Amino acids of endogenous origin are included in
  the amino acids captured at the distal ileum.
• EX 10 g lys was ingested, 1 g lys was lost from
  endogenous sources, 1.5 g lys in ileal fluids
• We calculate the digestibility at 85
• In reality, the digestibility was 95

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5.15 Apparent Ileal Digestibility Coefficient

• Because the digestibility coefficient, we
  measured at the distal ileum (85) is confounded
  by AA of endogenous origin, we call it Apparent
  Ileal Digestibility Coefficient (AID)

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5.16 Standardized Ileal Digestibility Coefficient

• If AID are corrected for the endogenous losses,
  then a standardized ileal digestibility
  coefficient (SID) can be calculated

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5.17 Calculating SID

• 10 g lys was ingested, 1 g lys was lost from
  endogenous sources, 1.5 g lys in ileal fluids
• AID (10 - 1.5)/10 x 100 85
• SID (10 - (1.5-1))/10 x 100 95

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5.18 Practical use of Digestibility Coefficients

• AID are better than total AA levels
• SID is more accurate than AID
• At present, AID is the method of choice
• In the Future, SID will be used

SID is sometimes called true digestibility