Ruminant Protein Systems and Requirements

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Ruminant Protein Systems and Requirements
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Ruminant protein requirement is a requirement for
metabolizable protein, not crude protein
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• Metabolizable protein supply dependent on
• Ruminally undegraded protein
• Microbial protein synthesis

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Calculating the Metabolizable Protein Supply

• Rumen degradable and undegradable protein
• Calculated from the rates of degradation of each
  protein fraction and the rate of passage of each
  feed.
• Feed protein fraction and range of degradability
• Fraction Definition Ruminal Kd,
  /hr
• A Soluble Infinity
• B Insoluble, but degradable
  .05-16
• C Insoluble, but not degradable 0

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Competition between degradation and passage

• protein degraded kd/(kd kp)
• protein passing kp/(kd kp)

Degraded
Kd
Feed protein In rumen
Kp
Passing (Undegraded)
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• Rates of ruminal passage, Kp
• Forages, Kpf 0.388 (22.0x/y.75) 0.0002z2
• Concentrates Kpc -0.424 (1.45Kpf)
• Where
• x Dry matter intake, kg/d
• y Shrunk body weight, kg
• z forage in diet
• Typical ranges
• Forages, 2 - 5 /hr
• Concentrates, 3 - 8/hr

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• Calculating the amount of protein degraded (RDP)
• RDP A BKd/(Kd Kp)
• Calculating the amount of ruminally undegraded
  protein (RUP)
• RUP BKp/(Kd Kp) C

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Example 1 How much degradable and undegradable
protein will be available from 1 kg of
solvent-extracted soybean meal with 50 crude
protein of which 20 is fraction A, 78 is
fraction B, and 2 is fraction C? Rate of
digestion for fraction B is 15/hr and the rate
of passage for SBM is 7.5/hr.

• Gm CP 1000 x .50 500 gm/kg DM
• Gm fraction A/kg DM 500 x .20 100
• Gm fraction B/kg DM 500 x .78 390
• Gm fraction C/kg DM 500 x .02 10
• Gm RDP/kg DM 100 390 15/(157.5) 360
• Gm RUP/kg DM 3907.5/(157.5)10 140

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Example 2 How much degradable and undegradable
protein will be available from 1 kg of
expeller-processed soybean meal with 50 crude
protein of which 20 is fraction A, 78 is
fraction B, and 2 is fraction C? Rate of
digestion for fraction B is 5/hr and the rate of
passage for SBM is 7.5/hr.

• Gm CP 1000 x .48 500 gm/kg DM
• Gm fraction A/kg DM 500 x .20 100
• Gm fraction B/kg DM 500 x .78 390
• Gm fraction C/kg DM 500 x .02 10
• Gm RDP/kg DM 100 390 5/(57.5) 256
• Gm RUP/kg DM 3907.5/(57.5)10 244

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• Ruminally undegraded feed proteins are assumed to
  be 80 digested in the small intestine

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• Microbial protein synthesis
• BCP (gm) .13 TDN (gm)
• Assumes
• TDN is corrected for fat
• RDP is adequate
• RDP requirement
• RDP 1.18 BCP (gm) - .2 diet CP (gm)
• If RDP lt 1.18 BCP .2 diet CP, then
• actual BCP (gm) .85 (RDP.2(CP)) (gm)
• BCP is assumed to be 80 protein which has a
  digestibility of 80 in the small intestine

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• Calculating metabolizable protein supply in
  ruminants
• MP(gm) RUP(gm) x .8 (.13 x TDN(gm)) x .8 x .8
• TDN is corrected for fat

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Example 1 How many gm of metabolizable protein
will a steer consume from the following diet?

• Feed kg DM cTDN, gm/kg RDP, gm/kg RUP,
  gm/kg
• Corn silage 2 680
  64 16
• Corn 7 780
  60 40
• SBM (solvent) 1 820
  360 140
• Diet TDN, gm/d (2 x 680) (7 x 780) (1 x
  820)
• 7640
• RUP, gm/d (2 x 16) (7 x 40) (1 x
  140)
• 452
• MP, gm/d 452 x .8 (7640 x .13) x
  .8 x .8
• 362 636
• 998

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Example 2 How many gm of metabolizable protein
will a steer consume from the following diet?

• Feed kg DM cTDN, gm/kg RDP, gm/kg RUP,
  gm/kg
• Corn silage 2 680
  64 16
• Corn 7 780
  60 40
• SBM (expeller) 1 820
  256 244
• Diet TDN, gm/d (2 x 680) (7 x 780) (1 x
  820)
• 7640
• RUP, gm/d (2 x 16) (7 x 40) (1 x
  244)
• 556
• MP, gm/d 556 x .8 (7640 x .13) x
  .8 x .8
• 445 636
• 1081

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Amino Acid Composition Crude Protein or G/100g
CP
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TRANSPORT OF PLASMA AMINO ACIDS INTO CELLS

• Amino acid transport into cells by active
  transport from the small intestine
• No amino acid absorption from reticulorumen
• Transport enhanced by certain hormones
• Tissue
  Hormones
• Liver
  Epinephrine
• 
  Glucocorticoids
• Uterus
  Estradiol
• Muscle Growth
  hormone
• 
  Insulin
• 
  Testosterone
• Amino acid pool in cells for metabolism comes
  from dietary amino acids and protein degradation
  in the animal

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Utilization of Absorbed Amino Acids

• Transported via portal vein to liver
• Used for synthesis of proteins in liver
• Metabolized (deaminated) - Used for
• energy Carbon for glucose
• Escape the liver
• Transported by blood to body tissues
• Used for synthesis of tissue proteins,
• milk, fetal growth, wool
• Metabolized - Used for energy

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Hormonal Control of Amino Acid Utilization
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Requirements for Absorbed Amino
AcidsMetabolizable Protein (MP)

• Protein (amino acid) requirements
• Maintenance
• Growth
• Lactation
• Pregnancy
• Wool

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Maintenance Requirement for Amino Acids

• Protein required to support zero gain or
  production
• Components of maintenance requirement
• Endogenous urinary N
• N loss resulting from amino acid metabolism
• Scurf proteins
• N loss from body surface (hair, skin, secretions)
• Metabolic fecal N
• N loss from undigested digestive secretions and
  fecal bacteria
• Maintenance requirement (Beef cattle)
• 3.8 g MP/kg BW.75

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MP Requirements for Growth

• Equation 1
• MP, g/d SWG (268 - (29.4 (RE/SWG)))/.49
• SWG Shrunk weight gain, kg/d
• RE Retained energy, Mcal/d
• Equation 2
• MP, g/d SWG ( protein in gain)/.49

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MP Requirements for Milk Production

• MP, kg/d Milk yield, kg/d x Milk protein/.67

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Situations Increasing Protein Requirements of
Ruminants
Situation Consequences 1. Young
animals Leaner gain Fast rate of gain
More total protein Leaner gain in
tissues 2. Compensatory gain Greater muscle
growth 3. High levels of lactation More milk
protein 4. Hormone implants and bGH More protein
synthesis 5. Low feed intakes Less MP from diet
High energy diets and microbes Need to
feed higher concentrations of protein or less
degradable protein
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Protein Requirements of Growing CattleChanges
with Increase in Weight
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Changing SBM Supplement to Urea Phase Feeding
Yearling steers, Revalor implant Cattle
require less protein as they approach mature
finished weights Industry standard is 13.5 to 14
crude protein for finishing cattle
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Value of Phase Feeding Finishing Beef Cattle

• Economic
• Environmental
• Example (680-1377 lb)
• 1-phase 3-phase 4-phase
• Diet(s) CP, 14.0 13.8 13.5
• 12.3
  12.2
• 11.6
  11.2
• 
  10.5
• N excretion, 418 313
  283
• tons/10,000 hd