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Microbial protein

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					Microbial protein
  By: Khalil Safaei
 (PhD stuendt of ruminant
        nutrition)
Sources of nitrogen in the rumen

 n   Dietary crude protein (true protein and NPN).
 n   Recycled microbial protein (bacteria and
     protozoa).
 n   Endogenous N (urea, abraded epithelial cells,
     salivary proteins).
Salivary Urea                           Recycled urea
                                                                          NH3      UREA

                                                                    nia         LIVER
                                                                 mo
                               NPN
                                                             d Am
                                                            e
                                                        iliz
                                                   n -ut
        Dietary
        Nitrogen                                No
                           PEPTIDES       NH3      LEVEL TO                       AMINO
                                                   PROVIDE FOR
                                                                                  ACIDS
                65%            AMINO     POOL      MAXIMUM
                      OF        ACIDS              MICROBIAL GROWTH
                           PR
                   RD        OT
                                 EIN
                                                                                    AMINO
                                                                                    ACIDS
                           P             MICROBIAL                      PROTEIN
                                         PROTEIN
                                                                           SMALL
                                                                           INTESTINE

                                  35% OF PROTEIN
                                        RUP


                       Reticulo-rumen
Peptides and amino acids
n 20 to 50% of ruminal microbial N is derived
  from this pool.
n Supplying preformed peptides and amino acids
  spares the cost associated with synthesizing
  amino acids.
n Availability of peptides improves microbial
  growth.
    Provision of High Quality Protein
n   50-80% of absorbed N is from microbes
    n   Improved microbial efficiency will provide
        more microbial protein
n   High biological value protein source
    n   Amino acid pattern is very similar to that
        required by the ruminant animal
Why Meeting the protein requirements
of ruminant animals is important?
Protein Degradation in Rumen
   Feedstuff        % Degraded
                     in 2 hours
      Urea               100
  Alfalfa (fresh)       90
  Wheat Grain           78
  Soybean Meal          65
   Corn Grain           48
   Blood Meal           18
Rumen Protein Utilization
n   Factors affecting ruminal degradation
    n   Rate of passage
         n                    Þ
             Rate of passage ­ degradation ¯
    n   Solubility in water
         n   Must be solubilized prior to degradation
    n   Heat treatment
         n   Degradation ¯
    n   N (and S) availability
    n   Energy availability (carbohydrates)
          Microbial Protein Formation
     Dietary                 Dietary Cellulose
     Starch Sugar            Hemicellulose
           rapid                 slow

Dietary
                   Carbon Skeletons           Sulfur   Other Co-factors
NPN
 rapid
          NH3                                                     Microbial
                                                                  Proteins
                                        ATP
   Amino Acids
 slower            very   Dietary
 Dietary           slow   Insoluble RDP
 Soluble RDP
                     Amino Acid Composition
                   % Crude Protein or G/100g CP


                Tissue Milk      ----------Bact ----------    Corn   Soy
                              Cell wall Non wall Mean
Methionine      1.97   2.71    2.40         2.68       2.60   2.28   1.46
Lysine          6.37   7.62    5.60         8.20       7.90   3.03   6.32
Histidine       2.47   2.74    1.74         2.69       2.00   3.16   2.72
Phenylalanine   3.53   4.75    4.20         5.16       5.10   5.32   5.65
Tryptophan      0.49   1.51     NA          1.63         -    0.89   1.46
Threonine       3.90   3.72    3.30         5.59       5.80   3.67   4.18
Leucine         6.70   9.18    5.90         7.51       8.10   12.66 7.95
Isoleucine      2.84   5.79    4.00         5.88       5.70   3.67   5.44
Valine          4.03   5.89    4.70         6.16       6.20   5.32   5.65
Arginine        3.30   3.40    3.82         6.96       5.10   5.06   7.53
Factors Influencing Microbial Protein
Synthesis
Ammonia
n Most important source of N for bacterial protein synthesis.

n 50 to 80% of bacterial N is derived from ammonia.

n Bacteria  hydrolyzing structural carbohydrates utilize
  ammonia as N source.
n Several mechanisms for the uptake of ammonia:

    n   high affinity, low Km (ammonia concentration) enzyme system
        glutamate synthetase - glutamate synthase (GS-GOGAT)
    n   lower affinity, higher Km system
        NADP-glutamate dehydrogenase (NADP-GDH), NAD-GDH and
        alanine dehydrogenase.
n   Minimum level of ammonia is necessary for maximum
    growth and efficiency (5 mg/100 ml of rumen fluid).
      Optimal Environment (pH)
n   If pH 5.7 rather than 6.5
     n 50% less microbial synthesis

     n Cellulolytic bacteria function best at pH ~6.8

        n Rate of structural carbohydrate use is decreased

     n Amylolytic bacteria function best at pH ~5.8

        n More lactate and less acetate is produced

        n Further downward pH spiral
                      Efficiency of Microbial Growth
                 14

                 12
BCP/100 gm TDN


                 10

                 8

                 6     Rate of passage                pH
                 4

                 2

                 0
                          55                         70
                               Diet % of TDN (DOM)
                Microbial Protein Synthesis
                n   Synchronization of carbohydrate and N availability
                    n   NPN supplementation
                    n   Carbohydrates used for carbon skeleton of amino acids
Concentration




                                                          VFA (CHO fermentation)

                                                          Blood NH3
                                                          Rumen NH3
                                                              Carbon backbone
                                                              (from CHO fermentation)
                          Time post-feeding
  Efficiency of Microbial Growth
Grams microbial N/100 g organic matter digested
Ranges from 1.1 to 5.0

  1.   Kind of diet     Forages > Grain
  2.   Level of feeding High > Low
  3.   Rate of passage Fast > Slow
  4.   Turnover of microbial cells
       Younger cells turnover less than aging cells
  5. Maintenance requirement of cells
       Microbes use energy to maintain cellular integrity
  6. Energy spilling
       Dissipation of energy different from maintenance
       Most apparent when energy is in excess
Degradation of nitrogenous compounds
by ruminal microorganisms
Bacteria
n   30 to 50% of the bacteria are proteolytic.
n   Most species have some activity with the exception of
    the main cellulolytic bacteria (Fibrobacter
    succinogenes, Ruminococcus flavefacians, R. albus).
n   Major proteolytic bacteria: Ruminobacter
    amylophilus, Butyrivibrio Fibrisolvens and Prevotella
    ruminicola.
n   P. ruminicola is the most numerous proteolytic
    bacteria (> 60% of ruminal bacteria) with strains that
    occur on both roughage and mixed roughage-
    concentrate diets.
Bacteria cont’d
n   R. amylophilus is the most active proteolytic bacteria.
    Important on starch-based diets.
n   Breakdown of both soluble and insoluble protein in the
    rumen.

Protozoa
n   Minor involvement in soluble protein breakdown.
n   Engulf and hydrolyze particulate proteins and bacteria.
n   Predatory activity of protozoa against rumen bacteria
    contributes to bacterial protein degradation and
    turnover in the rumen.

Fungi
n   Minor role in protein degradation.
Influence of diet on proteolysis

Concentrate
n   Increase in total microbial population,
    including several of the more active protein
    degrading bacteria which are also amylolytic
    (Prevotella rumincola, Ruminobacter
    amylophilus and Streptococcus bovis).
Fresh forage
n   Increase in the proportion of proteolytic
    bacteria relative to total microbial population.
   Composition of microbial protein reaching the intestine
                               Hay                  Hay and Conc
                          sheep 1     sheep 2      sheep 1    sheep2
N in rumen digesta, g
   Fungi                  .21          .60          .42      .69
   Protozoa              8.0          5.86       18.3     11.5
   Bacteria            11.5         10.4           9.03    8.07
N in rumen digesta, % of total microbial N
   Fungi                 1.1          3.6          1.5     3.4
   Protozoa            40.7         34.7         65.9     56.7
   Bacteria            58.3         61.7         32.6     39.8
N in duodenal digesta, g
   Fungi                  .10          .22          .21      .49
   Protozoa               .55         1.08         1.83    1.63
   Bacteria            13.1         14.6         10.1     15.9
N in duodenal digesta, % of total microbial N flow
   Fungi                  .73         1.4          1.7     2.7
   Protozoa              4.0          6.8        15.1      9.0
   Bacteria            95.3         91.8         83.2     88.2
Thank you

				
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posted:2/19/2014
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