proteins20_20ruminants1 (1).ppt
Post on 02-Jun-2018
218 Views
Preview:
TRANSCRIPT
-
8/10/2019 proteins20_20ruminants1 (1).ppt
1/32
More appropriate:
Rumen Nitrogen Metabolism
-
8/10/2019 proteins20_20ruminants1 (1).ppt
2/32
-
8/10/2019 proteins20_20ruminants1 (1).ppt
3/32
Protein Pathways in the Ruminant
-
8/10/2019 proteins20_20ruminants1 (1).ppt
4/32
General Information
No proteases in saliva No rumen secretions
Microorganisms responsible for protein
digestion in rumen (and reticulum) Bacteria
Protozoa
-
8/10/2019 proteins20_20ruminants1 (1).ppt
5/32
Sources of Rumen Nitrogen
Feed Protein nitrogen
Protein supplements (SBM, CSM, grains, forages,silages...
Nonprotein nitrogen (NPN)
Usually means urea
However, from 5% of N in grains to 50% of N in
silage and immature forages can be NPN
Endogenous (recycled) N
Saliva
Rumen wall
-
8/10/2019 proteins20_20ruminants1 (1).ppt
6/32
Ruminal Protein Degradation
Fermentative digestionenzymes ofmicrobial origin
MO proteases & peptidases cleave peptidebonds and release AA
AA deaminated by microbes, releasing NH3andC-skeleton
MOs use NH3, C-skeleton and energy to
synthesize their own AA Energy primarily from CHOs (starch, cellulose)
Formation of NH3rapid...very few free AA in
rumen
-
8/10/2019 proteins20_20ruminants1 (1).ppt
7/32
NPN Utilization
Urea (and most sources of NPN) rapidlydegraded to NH3
MOs dont care where NH3comes from
-
8/10/2019 proteins20_20ruminants1 (1).ppt
8/32
Limitations of Microbial Protein Synthesis
Two most likely limitations Energy available
NH3available
These need to be synchronized
For diets containing urea, may also need
Sulfur (for S-containing AA)
Branched-chain C-skeletons
MO cannot make branched-chain C-chains
These normally not a problem
-
8/10/2019 proteins20_20ruminants1 (1).ppt
9/32
Overflow Ammonia
Shortage of energy relative to available NH3
Liver: NH3Urea
Urea recycled or excreted, depending on
animal needs Saliva
Rumen wall
-
8/10/2019 proteins20_20ruminants1 (1).ppt
10/32
Protein Leaving Rumen
Microbial protein Escape protein (also called bypass protein)
Enter abomasum & small intestine Digested by proteolytic enzymes similar to
nonruminants
Escape vsBypass protein
Technically not bypass
Reticular groove
-
8/10/2019 proteins20_20ruminants1 (1).ppt
11/32
Protein UtilizationRuminant vsNonruminant
Similarities and Dissimilarities
-
8/10/2019 proteins20_20ruminants1 (1).ppt
12/32
Ruminant vsNonruminant - Similarities
1. At tissue levelMetabolic pathways similar2. Ruminant tissues can synthesize dispensable AA
3. Cannot synthesize indispensable AA
Essential AA must be provided from digestive tract
4. Tissue proteins constantly undergoing turnover
5. AA not stored
6. Constant supply of AA required
-
8/10/2019 proteins20_20ruminants1 (1).ppt
13/32
Ruminant vsNonruminant - Dissimilarities
1. Microbial population has profound effect on AAreaching S.I.
a. AA profile at S.I. different from diet
Up-grades low quality dietary protein
Down-grades high quality dietary protein
b. Enables ruminants to use NPN efficiently
Ruminants can be productive without a source of
dietary true proteinc. Animal can survive on low amounts of dietary protein
by recycling N (as urea) back to rumen
-
8/10/2019 proteins20_20ruminants1 (1).ppt
14/32
Ruminant vsNonruminant - Dissimilarities
1. Microbial population has profound effect on AAreaching S.I. (cont.)
d. Why we say nitrogen metabolism (vsprotein metab.)
Microbial intervention
NH3formation
e. Disadvantage: more protein can be destroyed in therumen than is synthesized
Result = Net lossof protein
Advantage: can have more protein leaving rumenthan is in the diet
Result = Net gainof protein
-
8/10/2019 proteins20_20ruminants1 (1).ppt
15/32
Example: More Protein Leaving Rumenthan was in Diet
Weston & Hogan (Australia) first to show this Fed sheep 2 diets containing 20% and 8% CP
20% Lucerne (alfalfa), corn, PNM
8% Wheaten hay, corn
Diets supported identical wool growth
Net gainNet loss
8.18.85.513.8
N entering S.I. vsdiet
AA-N entering S.I. (gm/day)
N fed (gm/day)
8% CP20% CPMeasurement
-
8/10/2019 proteins20_20ruminants1 (1).ppt
16/32
Ruminant vsNonruminant - Dissimilarities
2. In ruminant nutritiongenerally not concernedwith AA composition of dietary protein
a. Type of feed does not affect AA comp. of bacteria andprotozoa leaving rumen
AA comp. of MOs reaching duodenum strikinglysimilar when measured in labs around the world
b. Biological value (BV) of microbial protein ~80%
-
8/10/2019 proteins20_20ruminants1 (1).ppt
17/32
Matching Available Energy withRates of Protein Degradation
To maximize efficiency of microbialprotein synthesis from ammonia,available energy must be present.
-
8/10/2019 proteins20_20ruminants1 (1).ppt
18/32
Rumen NH3Following Protein Ingestion
-
8/10/2019 proteins20_20ruminants1 (1).ppt
19/32
Rumen VFA from Carbohydrate Sources
-
8/10/2019 proteins20_20ruminants1 (1).ppt
20/32
Matching Proteinand
Energy Sources
-
8/10/2019 proteins20_20ruminants1 (1).ppt
21/32
Protein Supplements for Beef Cows
Type of feed used for beef cows?
Would urea be utilized?
Why is urea included in range pellets?
-
8/10/2019 proteins20_20ruminants1 (1).ppt
22/32
Range Pellets
with NPN
-
8/10/2019 proteins20_20ruminants1 (1).ppt
23/32
Range PelletsNo NPN
-
8/10/2019 proteins20_20ruminants1 (1).ppt
24/32
Feeding Urea - Beef
Feedlot cattle (fed grain or silage diets) Up to 650-750 lb, use natural protein (SBM, CSM)
Cant consume enough for MOs to meet protein needs
>650-700 lb, urea = natural protein as N sourceAbove 0.75% urea in diet DM, start observing
palatability problems (intake)
General recommendation...
dont exceed 1% urea in diet
-
8/10/2019 proteins20_20ruminants1 (1).ppt
25/32
Will urea meet the needs of steers at all weights?
Diet 74% corn, 15% fescuehay, urea, molasses,minerals
Weight (lb)
450 675 900
Daily intake (lb) 11 16.5 18
Daily gain (lb/day) 2.5 2.9 2.2
MP required (gm/day) 512 585 506
MP available (gm/day) 430 639 685
% of MP requirementavailable
89% 109% 135%
-
8/10/2019 proteins20_20ruminants1 (1).ppt
26/32
Feeding Urea - Dairy
Dairy cows Upper limit ~1% of diet DM
Palatability begins to limit intake
-
8/10/2019 proteins20_20ruminants1 (1).ppt
27/32
Urea
Urea = 281% CP equivalent N = 45% of urea
45%N x 6.25 = 281% CP
How can urea have >100% CP?
Does this mean anything practical or
is it just academic?
-
8/10/2019 proteins20_20ruminants1 (1).ppt
28/32
Urea Toxicity (NH3Toxicity)
Mechanism Rumen [NH3] Rumen pH
As pH , shift from NH4+to NH3
NH3absorbed faster than NH4+
Liver capacity to convert NH3to urea isexceeded
NH3
goes to blood
2 mg NH3/100 ml plasma is toxic
-
8/10/2019 proteins20_20ruminants1 (1).ppt
29/32
Urea Toxicity (NH3Toxicity)
Signs of toxicityAppear 20-30 min after urea ingestion
Rapid and labored breathing
Tremors Incoordination
Inability to stand & tetany increasinglyapparent
-
8/10/2019 proteins20_20ruminants1 (1).ppt
30/32
Urea Toxicity (NH3Toxicity)
Treatment Orally dose with 5% acetic acid
(~1 gal. for 1,000 lb cow)
Shift equilibrium from NH3
to NH4
+
rate of absn
Drench with cold water
rumen temp. which rate of urea hydrolysis Dilutes NH3concentration
Takes 6-12 gal.; not practical when several sick
-
8/10/2019 proteins20_20ruminants1 (1).ppt
31/32
Urea Toxicity (NH3Toxicity)
Prevention Mix feeds well
Dont switch rapidly from natural protein to
ureaAlways have feed available
Dont allow hungry animals access to highlypalatable, high urea diet, feed, or
supplement (including lick tanks)
Dont use urea with low-energy feeds
-
8/10/2019 proteins20_20ruminants1 (1).ppt
32/32
Energy pathways in the Ruminant
top related