Rumen degradable Protein (RDP), and rumen undegradable

protein (UDN) and Kinetics

Vishnu Vardhan Reddy.PTVM/2015-029

Department of Animal nutritionCollege of Veterinary Science, TirupatiSri Venkateswara Veterinary University

Digestion of protein

Fate of Rumen Ammonia

1. Bacterial protein synthesis

2. Absorbed from reticulorumen and omasum

NH3 passes from rumen by diffusion into portal blood.

Form of ammonia dependent on pH of rumen

NH3 + H+ NH4+

Less absorption at more acid pH

3. At pH of rumen, no NH3 lost as gas

Fate of Absorbed Ammonia

1. Transported to liver by portal vein

2. Converted to urea via urea cycle in liver

3. Urea released into blood

4. If capacity of urea cycle in liver is exceeded causes Ammonia toxicity

Fate of Blood Urea1. Excreted into urine

2. Recycled to digestive tract, g N/d

• Saliva – Related to concentration of urea in blood

Sheep: 0.5 to 1.0

Cattle: 1.0 to 7.6

• Diffusion into GIT

Sheep: 2 to 5

Cattle: 25 to 40

Adjustments to Low Protein Intake

Urea is predominant form of nitrogen in urine

Reabsorption of urea by kidney increased when ruminants fed low

nitrogen diets

• Conserves nitrogen in the body

• Greater portion recycled to digestive tract

• Sheep fed the same diet tend to reabsorb more urea than cattle

Fate of Free Amino Acids in the Rumen

1. Amino acids not absorbed from the rumen

• Concentrations of free AA in the rumen very low

2. Amino acids and small peptides (up to 5 AA) transported into

bacterial cells

• Na pumped out of cells – Uses ATP

• Na gradient facilitates transport of AA by a carrier

3. Utilized for synthesis of microbial proteins

4. Amino acids metabolized to provide energy

Fractions of dietary protein

• Rumen degradable Protein (RDP)

• Rumen undegradable protein (UDN)

• Rumen Degradable Protein (RDP) is the fraction of Crude Protein (CP)

consumed which is broken down by rumen microbes.

• And remaining protein which reaches the small intestine without

degradation called as Rumen undegradable protein (UDN).

Protein Fractions In Feeds (CNCPS system)

A - Soluble in buffer (borate-phosphate) and not precipitated by

tungstic acid

B1 - Soluble in buffer and precipitated by tungstic acid

B2 - Insoluble in buffer = (Insol protein) - (protein insol in neutral

detergent)

B3 - Insoluble in buffer = (Insol in neutral detergent) - (Insol in acid

detergent)

C - Insoluble in buffer and acid detergent

Digestion of Rumen degradable Protein (RDP)

• Rumen degradable Protein (RDP) hydrolysed to peptides and amino acids

by rumen microorganisms, but some amino acids are degraded further,

to organic acids, ammonia and carbon dioxide.

• The main proteolytic organisms are Prevotella ruminicola,

Peptostreptococci species and the protozoa.

• Two major steps are involves in protein degradation in the rumen:

1- Hydrolysis of peptide bonds to produce peptides and amino acids

2- Deamination and degradation of amino acids

• The ammonia produced due those processes , together with some

small peptides and free amino acids, is utilised by the rumen

organisms to synthesise microbial proteins.

• Some of the microbial protein is broken down in the rumen and its

nitrogen is recycled (i.e. taken up by microorganisms).

• The new NRC (2001) suggests that maximum milk and milk protein

yields occur when RDP is 12.2% of diet dry matter.

• An important feature of the formation of microbial protein is that

bacteria are capable of synthesising indispensable as well as

dispensable amino acids, thus rendering their host independent of

dietary supplies of the former.

• The ammonia in rumen liquor is the key intermediate in microbial

degradation and synthesis of protein.

• Estimates of the optimum concentration of ammonia in rumen liquor

vary widely, from 85 mg/l to over 300 mg/l.

• If the food is poorly supplied with protein and the concentration of

ammonia in rumen liquor is low, the quantity of nitrogen returned to

the rumen as urea from the blood may exceed that absorbed from the

rumen as ammonia.

• This net gain in ‘recycled’ nitrogen is converted to microbial protein,

which means that the quantity of protein reaching the intestine may be

greater than that in the food.

• With most feeds each kilogram of organic matter digested in the rumen

yields approximately 200 g of microbial protein.

Rumen undegradable protein (UDN) digestion

• Rumen undegradable protein (UDN) is also called bypass protein or escaped

protein or rumen undegradable protein (RUP).

• It is the portion of intake protein that escapes rumen degradation and is

digested directly in the small intestine.

• About 80 to 85 per cent of the microbial bacterial protein and UIP or true

protein that flows out of the rumen is digested in the small intestine and it is

expressed as a percentage of crude protein (CP).

Protein digestion in the small intestine

• The nitrogen entering the duodenum is a combination of microbial protein,

undegraded protein and endogenous protein. Nitrogen entering the small

intestine from the stomach can range from 30 to 100% microbial protein and 0

to 70% undegraded protein.

• Digestion of protein in the abomasum and the small intestine in ruminants is

similar to that in monogastric animals. The digestion of protein in the

abomasum is carried out mainly by pepsin in a very acidic environment (pH 2).

Absorption of amino acids and peptides

• The most active site of amino acid and peptide absorption is the mid

to lower ileum.

• There is a preferential absorption of essential over nonessential

amino acids from digesta flowing through the small intestine.

• For example, absorption of lysine and histidine is higher than the

absorption of leucine and phenylalanine.

Sources of Bypass Protein

1. Naturally Protected Proteins2. Heat Treatment3. Chemical Treatment4. Esophageal Groove5. Post Rumen Infusion (Fistula)6. Encapsulation of Proteins7. Amino Acids Analogs8. Lowering Ruminal Protease Activity9. Decreasing Retention Time in Rumen

Naturally Protected ProteinsFeed UDP %

Maize (grain) 65Barley 21( 11-27)Sorghum 52Bajra 68Oat grain 14–20Wheat grain 20–36Cotton seed meal 41–50Linseed meal 11–45Ground nut meal 30Rapeseed meal 23Soybean meal 28 ( 15–45)Sunflower meal 24Subabul 51 – 70

Feed UDP %Blood meal 76 – 82Fish meal 71 – 80Meat meal 53 – 76Brewers dried 53Corn gluten 53Wheat bread 29Corn silage 27Rice straw 63Wheat straw 45Para grass 52Cow pea 32 – 45Berseem 37 – 52Alfa-Alfa 28

(NRC, 1985; Dutta et. al., 1997)

Heat Treatment

• Heat processing of feed decreases protein degradation in the rumen

by denaturing proteins and the formation of protein–carbohydrate

cross-links called as Maillard reactions and protein–protein cross-

links.

(Animal Nutrition by McDonald seventh edition Pg.no:566)

• According to the article “Estimates of protein fractions of various

heat-treated feeds in ruminant production” by Ho Thanh Tham, Ngo

Van Man and T R Preston.

Heating the leaves to temperatures of

140°C for 2 hours reduced the proportion of the protein in the A and

B2 fractions and increased the B3fraction.

Chemical Treatment

1) Formaldehyde treatment

2) Lignosulfonate treatment

3) Xylose Treatment

4) Tannic acid treatment

Formaldehyde treatment

• Formaldehyde treatment of high quality proteins result in the

formation of cross-links with amino group and makes the protein

less susceptible to microbial attack (Czerkawski, 1986).

• These bonds are highly stable in the near neutral pH of the rumen

but are readily hydrolyzed in the acidic pH of the lower digestive

tract.

• According to the article “Effect of processing on protection of highly

degradable protein sources in steers” by M.Yugandhar Kumar and A.Ravi.

Heat treatment is better for reducing EDP of Rape seed meal,

and Coconut cake Formaldehyde treatment for mustard cake, Tobacco

seed cake, Heat or HCHO treatment for Babul seed meal, Rape seed

meal, and Mustard cake.

Dried poultry waste and guar meal were resistant to different

processing methods.

Extrusion cooking was least effective of the three methods.

Lignosulfonate treatment

• In general, the term "Lignosulfonate" is used to describe any product

derived from the spent sulfite liquor that is generated during the

sulfite digestion of wood and containing a percentage of lignosulfonic

acid or its ash as well as hemicellulose and sugars.

(Windschitl and Stern, 1988)

• Because lignosulfonates can bind and precipitate protein, it was

hypothesized that protein meal treated with lignosulfonates could be

rendered less degradable in the rumen.

• It was concluded that heat and the presence of wood sugars in the

lignosulfonate preparation were necessary for a positive response.

(Windschitl and Stern, 1988)

Xylose Treatment

• Combination of heat and xylose enhances non-enzymic browning

(Maillard reactions) due to the increased availability of sugar

aldehydes that react with the protein.

Cleale et al. found that treatment of soybean meal with xylose (3 mol

xylose/mol lysine) was effective in reducing degradation of soybean

protein by rumen microorganisms.

(Animal Nutrition by McDonald seventh edition Pg.no:566)

Tannin treatment

• The main effect of tannins on proteins is based on their ability to form

hydrogen bonds that are stable between pH 3.5 and 8

(approximately). These complexes stable at rumen pH dissociate

when the pH falls below 3.5 (such as in the abomasum, pH 2.5-3) or

is greater than 8 (for example in the duodenum, pH 8).

(S. J. Bunglavan and N. Dutta)

Esophageal Groove

• This is normal function in young one. It is done/ good for liquid

proteins.

• Surgically fitted fistula after the rumen in the lower tract of intestine

is an easy method to avoid rumen microbial degradation of proteins,

so proteins/ amino acids are available in the intestine.

Post Rumen Infusion (Fistula)

Encapsulation of Proteins

• Encapsulation of Proteins is usually done for good Biological value

proteins and for individual amino acids.

• They can be given the form of capsule with a combination of fats or

fatty acids sometimes by addition of carbonate, kaolin, lecithin,

glucose etc.

Amino Acids Analogs

• Structural manipulation of amino acids to create resistance to ruminal

degradation is another potential method for rumen bypass of amino

acids.

• Analogs such as Methionine hydroxy, N-acetyl-DL-Metionine,

DLHomocysteine thiolactone-Hcl, DL-Homocysteine, etc. have given

satisfactory results.

Lowering Ruminal Protease Activity

• By depressing the proteolysis activity of the rumen microbes we can

slow down the protein degradation within the rumen.

• Bacteria are the mainly responsible for proteolytic degradation.

• So antibiotics can be used to reduce the protein degradation within

the rumen.

Decreasing Retention Time in Rumen

• Less the time in rumen environment causes less degradation. Faster

pass of feed in the rumen is the explanation.

• Factors influencing the rate of passage include food intake, specific

gravity, particle size, Concentrate to roughage ratio, rate of rumen

degradation etc.

Factors Affecting Ruminal Protein Degradation

Chemical Nature of the proteins

• Solubility – More soluble proteins degraded faster some soluble

proteins not extensively degraded

Egg ovalbumin, serum proteins

• 3-dimensional structure – Affects solubility & availability

• Chemical bonding

Disulfide bonds – Reduces degradation

• Physical barriers

• Cell walls of plants

• Cross linking of peptide chains – Reduces degradation

E.g. Aldehydes, Tannins

• Feed intake

• Rate of passage – Time proteins remain in the rumen

• Feed processing

• Rate of passage

• Heat damage – Complexes with carbohydrates

Estimating Degradation of Dietary Proteins in the Rumen

1. In situ digestion

Feed placed in Dacron bags suspended in the rumen and measure

protein lost over time

2. Cannulated animals (rumen & duodenum)

Measure protein flowing through duodenum

Need to differentiate feed from microbes

3. In vitro incubation with rumen microbes

Relative differences among proteins

4. In vitro digestion with fungal enzymes

Protein Degradation

DIP (RDP) = A + B[Kd/(Kd+Kp)]

DIP = Degraded intake protein

Kd = degradation rate, %/h

Kp = passage rate, %/h

UIP (RUP) = B[Kp/(Kd+Kp)] + C

UIP = Undegraded intake protein

Kd Values for Feed Proteins

Fraction Kd, %/h

A Infinity

B1 120 to 400

B2 3 to 16

B3 0.06 to 0.55

C Not degraded

Kp ValuesWet foragesKp = 3.054 + 0.614X1Dry foragesKp = 3.362 + 0.479X1 – 0.007X2 – 0.017X3ConcentratesKp = 2.904 + 1.375X1 – 0.020X2

X1 = DMI, % Body WtX2 = Concentrate, % of ration DMX3 = NDF of feedstuff, % DM

Recommendations for Feeding High RUP Byproducts to Dairy Cows

CP RUP Recom intake

ByProd CP intake

ByProd CP intake

% % lb/d lb/d % total Blood meal 87 82 .75-1.0 .87 9.7 Feather meal 92 71 .5-1.0 .92 10.2 Meat & bone 54 70 2.0-2.5 1.35 15.0 Fishmeal 67 60 1.0-2.0 1.34 14.9 Corn gluten meal 67 55 2.0-3.0 2.01 22.3 Corn distill. grain 30 47 4.0-6.0 1.80 20.0 Soybean meal 52 33 Extruded SBM 49 61 Feed as needed Extruded soybeans 43 54 Oil intake might limit Roasted soybeans 43 62

Importance of Bypass Protein

Required for medium and high lactating and growing animals

mainly in early lactation.

Increase in Milk production by 10-15 %.

Good increase in live weight gain of meat purpose animals.

Exposes essential and limiting amino acids directly to Intestine.

Reduces Milk Production cost.

Why Limit High RUP Proteins in Lactating Cows

• Animal byproducts tend to reduce feed intake Palatability

Decreased feed intake reduces microbial protein synthesis

• Plant byproducts may have poor amino acid balance

Corn proteins deficient in lysine and

• Quality of RUP proteins can be variable

• Protein requirements may have been met

•First limiting amino acid might not be increased

•Overestimation of degradation of other supplemental proteins

THANK YOU

Vishnu Vardhan Reddy.PTVM/2015-029