nutrition - protein

Protein

Made up of amino acids

Essential AA (EAA)

• MATT

  • Methionine

  • Argenine

  • Threonine

  • Tryptophan

• HILL

  • Histidine

  • Isoleucine

  • Leucine

  • Lysine

• VP

  • Valine

  • Phenylalaline

EAA pt 2

• Not synthesized by body in sufficient amounts to meet animal’s requirements

• Must be absorbed from SI in proper quantities to optimize animal performance

• Expensive

• If overfed, AA metabolized to glucose/energy

Non essential AA (NEAA)

• Synthesized by mammal in sufficient amounts to meet animal’s requirements

• Required for normal metabolism

Ruminants and EAA

• Ruminants do not generally require EAA in diet because ruminal microbes capacity to synthesize all AA

• Ruminants do require EAA to be abs in small intestine

What do microbes require to synthesize AA’s?

• carbonskeleton (VFA) + ammonia (NH3)

Two types of weaned cattle, require EAA in excess ruminal microbes’ ability to synthesize EAA

A.) High production dairy cow

• Methionine, increase milk production

• Must protect methionine from microbial degradation

B.) Implanted (growth promotant) rapidly growing steers grazing wheat pasture

• Supply ruminally undegradible protein (microbes cannot degrade it)

Amino acid requirements - maintenance requirement

• Increase with increased size

• Increase with lean muscle mass (sex, more in males)

• Decrease with age

• Increase with increased production potential

  • Dairy > beef cow

Amino acid requirements - production requirement

• Increased with increase muscle growth

• Increased with increase gestation

• Increased with increase lactation

• Increase with fiber (wool, hair) production

• Increased with work

Peptide bond

• Bond between 2 AAs

Peptides

• Polypeptides >10 AA

• Tripeptides 3 AA, 2 peptide bonds

• Dipeptides 2 AA, 1 peptide bond

• AA, 1 AA, 0 peptide bonds

• Tripeptides, dipeptides, and AA are products of digestion absorbed by SI

Protein structure

• 1 degree= sequence of AA (breaking of peptide bonds, enzymatic hydrolysis

• 2 degree= hydrogen bonding between AA

• 3 degree= clustering of hydrophobic regions

• 4 degree= interaction between polypeptides

• 2-4 degree are denaturing proteins in stomach with HCL (low pH)

Non ruminant digestion steps

1. denaturation= denature proteins with acid (HCl) in stomach

   • exposes the peptide bond for enzymatic hydrolysis

   • Affects 2,3,4 structures

   • Can digest proteins without denaturing, less effective

2. Enzymatic hydrolysis of peptide bonds

   • occurs in stomach and SI primarily

   • Affects 1 degree structure

3. Absorption of dipeptides, tripeptides, AA

   • Use transporters on enterocyte

Non ruminant digestion - mouth and stomach

• Mouth: decreases particle size

• Stomach: uses HCl to decrease pH, denature protein (2,3,4)

  • Produces zymogens (inactive): pepsinogen

    • Pepsinogen with HCl or pepsin → pepsin

    • Pepsin irreversible, HCl reversible (goes away w higher pH)

  • Pepsin hydrolyzes peptide bonds

Zymogens

• Pepsinogen zymogen activated by HCl or pepsin to pepsin, site of activity is stomach, activity is endopeptidase

• Trypsinogen zymogen activated by enteropeptidase or trypsin to trypsin, site of activity is in SI, activity is endopeptidase

• Chymotrypsinogen zymogen is activated by trypsin to chymotrypsin, site of activity in SI, activity is endopeptidase

• Procarboxypeptidase zymogen is activated by trypsin to carboxypeptidase A&B, site of activity is in SI, activity is exopeptidase

• Trypsinogen, chymotrypsinogen, and procarboxypeptidase are all pancreatic zymogens

Activities

• Endopeptidase: hydrolyzes peptide bonds in interior of protein

• Exopeptidase: hydrolyzes peptide bonds on exterior of protein

Enteropeptidase

• Enteropeptidase (enterokinase): produced by enterocytes to activate trypsin

  • Released in response to CCK and secretin

• In lumen in duodenum, When I cells and S cells produce CCK and secretin, enterocytes react by producing enteropeptidase

• Pancreas reacts to CCK and secretin by producing zymogens and buffer (increase pH), helps breakdown denatured proteins and digesta

Peptidases

• Enteropeptidase= activates trypsin

• Aminopeptidase= cleaves 1 AA from oligopeptide

• Dipeptidylamino peptidase= cleaves dipeptides from oligopeptides

• Tripeptidase= cleaves 1 AA from tripeptides

Ruminant and non ruminant enterocyte - transporters

• NA+D: sodium dependent transporter

  • Similar to SGLT1

  • Transports against [AA] gradient

  • Preference for large EAA

• NA+i: sodium independent AA transporter

• PEPT1: peptide transporter1

• AAT: amino acid transporter

Ruminant and non ruminant enterocyte

• Na+D transporter brings in Na and AA into enterocyte

• Na+I brings AA into enterocyte

• PEPT1 brings in H+ (proton) and di or Tri peptide

• Na+H+ brings in Na+ and H+ into enterocyte

• AA used either for protein synthesis, NEAA for energy, or taken into AAT to blood/body

  • Used for protein synthesis

  • Energy (glc and ketones)

  • Some AA comes back into AAT

• BBE produced/abs in lumen:

  • Enteropeptidase

  • Aminopeptidase

  • Dipeptidylamino peptidase

  • Tripeptidase

Pig digestion of protein - mouth and stomach

• Mouth ingests protein and reduces particle size

• HCl is produced in stomach to denature proteins at 2,3,4 degree/stage

• Pepsinogen activated into pepsin by HCl or pepsin (denatures 1º of protein)

• After denaturing, proteins turn into oligopeptides (with low pH)

Pig digestion of protein - pancreas and duodenum of SI

• Duodenum produces S and I cells

  • S cells produce secretin which goes to enterocyte and pancreas

  • I cells produce CCK which goes to enterocyte and pancreas

• Pancreas then secretes zymogens and buffer (Na+HCO3)

  • Trypsinogen with Enteropeptidase or trypsin → trypsin

  • Chymotrypsinogen with trypsin → Chymotrypsin

  • Procarboxypeptidase with trypsin → carboxypeptidase A&B

• Enteropeptidase, made in enterocyte as peptidase, is active in duodenum

  
  

Pig digestion of protein - jejunum, enterocyte

• In jejunum, AA, dipeptides, and tripeptides are absorbed

• In enterocyte there are 5 active transporters:

  • Na+D, Na+i, PEPT1, Na+H+, AAT

• In enterocyte, peptidase hydrolyzes Tri and dipeptides to AA and exits/enters enterocyte through AA transporter (AAT)

  • BBE in enterocyte: aminopeptidase, dipeptidylamino peptidase, tripeptidase

  • NaKATPase present on enterocyte to maintain electrical gradient

  • AA then goes to liver through blood

  
  

Pig digestion of protein - liver, large intestine

• in liver, excess AA will be added into muscle as AA+ or returned back to liver as AA- (happens during fasting, lactating, become smaller)

• Excess AA can also be used as glucose and ketones for ATP or become NH3 to convert to urea

  • Travels through blood to become urine (N loss) or go to large intestine

• In large intestine, urea is absorbed and converted to NH3 again and sent back to liver through blood

• In LI, carbon skeletons (VFAs, which are absorbed in LI) and ATP produce mcp which is excreted

  • Undigested food and endogenous proteins also produce mcp or are excreted

  • Endogenous proteins = cells (enterocytes) or enzymes

Maintenance, growth, shrink

• Maintenance: AA+ = AA-, PS= PD

  • PS: protein synthesis (uses AA)

  • PD: protein degradation (frees AA)

• Growth: PS> PD, AA+> AA-

  • Increase PS and PD, but increase PS> PD

• Shrink: PS< PD, AA+ <AA- (lactating cow, sow)

  
  

Ruminant Protein Utilization - protein types

• RUP= ruminally undegradable protein (UIP, undegradable intake protein)

  • Microbes cannot degrade this type/ fraction of protein

  • Leaves rumen w/ the same AA profile as was fed

  • RUP about 80% digestible (range 0-100%)

• RDP= ruminally degradable protein (DIP, degradable intake protein)

  • Microbes degrade 100% of RDP, RDP used to synthesize mcp

  • Microbes alter/ change AA profile, RDP includes non protein nitrogen (npn), urea, ammonia, AA

Ratio of RDP to RUP

• Changes for feed stuff based on kP

• Increase kP → decrease RDP, increase RUP, shorter retention time

• Decrease kP → increase RDP, decrease RUP, longer retention time

• RDP supplies NH3 for synthesis of mcp and excess NH3 abs from rumen

Protein pathway, lumen to body

Ruminant Protein Utilization - mouth, rumen, abomasum, duodenum

• Mouth decreases particle size

• Protein ingested, in rumen, digested as RDP or RUP (escape protein)

• In abomasum, HCl is produced in stomach to denature proteins at 2,3,4 degree/stage

• In abomasum, Pepsinogen activated into pepsin by HCl or pepsin

• In duodenum, RUP then turns into oligopeptides (with low pH)

• In duodenum, enteropeptidase is produced

• Duodenum produces S and I cells

  • S cells produce secretin which goes to enterocyte and pancreas

  • I cells produce CCK which goes to enterocyte and pancreas

  
  

Ruminant Protein Utilization - pancreas,jejunum, enterocyte

• Pancreas then secretes zymogens and buffer (Na+HCO3)

  • Trypsinogen with Enteropeptidase or trypsin → trypsin

  • Chymotrypsinogen with trypsin → Chymotrypsin

  • Procarboxypeptidase with trypsin → carboxypeptidase A&B

• In jejunum, AA, dipeptides, and tripeptides are absorbed

• In enterocyte there are 4 active transporters:

  • Na+D, Na+i, PEPT1, Na+H+

• In enterocyte, peptidase hydrolyzes Tri and dipeptides to AA and exits/enters enterocyte through AA transporter (AAT)

  • BBE in enterocyte: aminopeptidase, dipeptidylamino peptidase, tripeptidase

  • NaKATPase present on enterocyte to maintain electrical gradient

  • AA then goes to liver through blood

RDP is fed to…

• … meet microbial requirements, most important

  • Microbes synthesize cells enzymes

  • Limited RDP prevents SCHO fermentation, decreased energy availability to the cow