GOALS TO MINIMIZE THE EFFECTS OF ANIMAL
PRODUCTION ON N LOADING OF THE ENVIRONMENT
• To meet the protein requirements of a specific class
of animal
• To minimize total N loss from the feeding system
– Feed waste
– Fecal loss
– Urinary loss
• Of the N excreted, have a higher proportion excreted
in the feces relative to the urine.
LOSSES OF DIETARY N FED TO NONRUMINANT ANIMALS
Retained
Feed offered
Feed consumed
Loss
Feed waste (Manure N increases 1.5%
for each 1% increase in feed waste)
Swine, % of consumed N
Undigested feed
15
Fecal
Endogenous secretions 8
N
Nutrients absorbed
Maintenance
Nutrients available for
growth or egg production
Lean growth or egg prod.
50
Urinary N
Imbalance
Inefficiencies (1/3 lb of
protein degraded/1 lb
protein gain)
_______
73% of
consumed N is wasted
DIETARY STRATEGIES TO REDUCE N LOADING OF
THE ENVIRONMENT BY NONRUMINANTS
• Reduce feed waste
– Animals can be sloppy eaters
– Amounts
• 5 – 6% of feed contributing 7.5% of the N in manure
– May be as high as 20%
– Strategies
• Feed pelleted feeds instead of mash
– Reduces feed waste by 5%
• Do not overfill feeders
– Amount of feed should be limited to cover 50% of the
feeder bottom (Swine)
– Fill feeder to 25% of height (Poultry)
• Properly position feeders
– Swine
» Utilize feeders that allow pigs to hold head straight
above feeder
– Poultry
» Top of feeder should be at the base of the neck
• Reducing water waste
– Problems
• Increases amounts of liquid handled in liquid manure systems
• Increases problems with NH3 production, bacteria and flies in
dry litter systems
– Strategies
• Fix water leaks
• Swine
– Place cups under nipple waterers
– Use liquid feeding systems
• Poultry
– Use efficient water nipples
– Adjust waterers to avoid spillage
• Increase the apparent digestibility of N
– Feed highly digestible protein sources
• Protein digestibility of corn and soybeans is approx. 85%
• Protein digestibility of raw soybeans is limited by trypsin inhibitor
• Protein digestibility of sorghum is limited by tannins
– Feed processing
• Grinding
– A uniform particle size of 700um is recommended for swine
• Pelleting, expanding, or extruding
– Reduces feed waste
– Provides heat
» Alters feed structure
» Destroys antinutritional factors
– Must be careful to avoid overheating
– Enzyme addition
• Results variable
• Proteases improve gains in pigs fed whole soybeans
• Fiber digesting enzymes will degrade non-starch polysaccharides
in barley and wheat
– Reduces viscosity
– Increases N digestibility
• Reduce endogenous N excretion
– May account for 26% of total N excretion
– Strategies
• Lower fiber content of the diet
– Reduces sloughing of intestinal cells
– Reduces bacterial fermentation in large intestine
• Heat treat soybeans to destroy trypsin inhibitor
– Increases protein digestibility
– Decreases protease secretion by the animal
• Precision feeding of protein
– Avoid feeding protein in excess of requirements
• Example (Feeding regimes for swine giving equal performance)
%CP in diets
Grower phase
17.8
17.8
16.2
Finisher phase
17.1
15.4
13.5
lb/pig
Manure N
6.3
5.8
4.9
Gaseous N
2.4
2.1
1.8
% reduction
Manure N
9
23
Gaseous N
12
25
• Advantages
– Reduces feed costs
– Reduces environmental N load
• Strategies
– Feed proteins for optimal gain, not necessarily maximum gain
– Minimize safety margins in dietary formulation
– Balance diets for available amino acids rather than crude
protein or total amino acids
• In poultry, decreasing CP by 2% while maintaining amino acids
decreased N excretion by 16%
• Difficulties
– Feed composition
» Considerable variability
» Book values are unsatisfactory
» Rapid analysis is difficult and expensive
– Animal requirements
» Differ between controlled research and in the field
» Requirements vary with:
Animal genetics
Sex
Stage of growth
Environmental temperature
Balance with other nutrients
Growth promotants – Ractopamine (Paylean)
– Balance for available amino acids
• Difficulties
– Current requirements are based on feeding mixtures of
corn and soybeans to meet the lysine requirement
» Results in overfeeding other amino acids
» Requirements not well-adapted for other feed
ingredients
• Strategy
– Utilize high quality protein sources or synthetic amino
acids to feed an ‘ideal’ protein
– An ideal protein has all of the essential amino acids in
amounts proportional to their requirements relative to
lysine
– Ideal amino acid pattern for pigs, % of lysine
Lysine
Threonine
Tryptophan
Methionine and Cystine
Isoleucine
Valine
Leucine
Phenylalaine and Tyrosine
Arginine
Histidine
10-45 lb 45-110 lb 110-240 lb
100
100
100
65
67
70
17
18
19
60
62
65
60
60
60
68
68
68
100
100
100
95
95
95
42
36
30
32
32
32
– Advantage
• Predicts amino acid requirements with changing
protein:energy ratio, temperatures, and genetic capacity for
lean growth
– Potential (200 lb swine)
14% CP
12% CP
Corn-soybean meal + lysine
_______
g/d
Retained N
Fecal N
Urinary N
Total N excreted
% reduction
26
7
34
41
-
_______
26
7
25
32
22
– Amino acids currently economically produced
•
•
•
•
Lysine
Methionine
Threonine
Tryptophan
10% CP
+ lysine
threonine
tryptophan
methionine
26
7
17
24
42
– Separate animals by sex and feeding phase
• Separate sex feeding
– Protein requirements
» Intact males>Castrated males>Females
• Phase feeding
– As animal grows, protein requirement decreases as a
percentage of diet
– Potential of phase feeding (Swine)
Diet CP, %
N excretion, lb/pig/day
Reduction
Feeding system
Single feed Two feeds Three feeds
17 (55-220 lb) 17 (55-120 lb) 17 (55-110 lb)
15 (120-230 lb)15 (110-165 lb)
12 (165-230 lb)
.07
.064
.059
8.6
15.8
– Typical number of phases
» Swine 3-4
» Broilers 4
» Turkeys 6
– Limited by feed storage and handling
• Enhance lean growth (Swine)
– Mechanism
• Increases incorporation of amino acids into protein
• Reduces the effects of the maintenance requirement
– Strategies
• Genetically lean pigs
• Feed Ractopamine
– Sold as Paylean for pigs
– Used at 18 g/T for 150 to 240 lb (5 weeks)
» Effect decreases after 4 weeks
» Can’t be used longer than 90 days
– Mechanism
» Shifts energy from fat deposition to muscle growth in
ham, loin, belly and shoulder
– Effects
» Increases feed efficiency – 12%
» Increases daily gain – 10%
» Increases lean gain – 25- 37%
» Decreases N excretion by 11 to 34%
– Greatest improvement in genetically lean pigs
CONSIDERATIONS TO LIMIT N EXCRETION BY RUMINANTS
• Supply adequate degradable N to meet ammonia
needs of rumen microbes
• Supply adequate metabolizable protein to meet the
amino acid needs of the animal for maintenance and
production
• Major limitation
– Proportion of total protein that is degraded or undegraded
varies in feed
• Results in excess degradable protein being fed to meet
undegradable protein needs
• Example
A feedlot steer needs 2.5 lb of metabolizable protein per day
from a diet that supplies 1.5 lb of microbial protein per day if
adequate degradable protein is fed. Therefore, the steer needs
1 lb of undegradable protein from a supplement.
Amounts of supplement needed and resulting N excess:
Undegraded protein
Needed CP
Excess N
Supplement
% CP
obtain 1 lb undegraded CP from supplement
Corn
50
2
.16
Corn silage
30
3.3
.37
Alfalfa silage
20
5
.64
Urea
100
∞
∞
STRATEGIES TO REDUCE N EXCRETION BY
RUMINANTS
• Increase microbial protein production in the rumen
– Maximize feed intake
• High quality feed ingredients
• Properly balanced diet
– Adequate fiber
– Adequate minerals
– Avoid excess fat
• Proper adjustment to dietary changes
– Feed highly digestible grains
• Grain species
– Barley>Corn or sorghum
• Grain variety
– Waxy corn > normal corn
• Grain processing
– Grinding
Digestibility of corn 5 – 10%
– Steam-flaking
Digestibility of corn 10 – 20%
– Ensiling (High moisture) Digestibility of corn 10%
– Feed forages with high digestibility, but low concentration of
degradable protein
Low
Medium
Digestibility
High
Corn silage
Alfalfa silage
Alfalfa hay
Grass hay
Grass or grass-legume pasture
Crude protein
Corn silage
Alfalfa silage
Alfalfa hay
Grass hay
Grass or grass-legume pasture
Ruminal degradability of protein
Corn silage
Alfalfa silage
Alfalfa hay
Grass hay
Grass or grass-legume pasture
– Balance other nutrients needed for microbial growth
• Sulfur
– Need a 10:1 N:S ratio
• Balance supply of rumen degradable protein and
undegraded protein
– Supplemental protein source dependent on forage protein
degradability and energy level
– If forage contains a highly degraded protein and moderate energy (like
alfalfa silage), then feed a protein supplement with low ruminal
degradability.
– If forage contains a protein with low to moderate degradability and high
energy level (like corn silage), then feed a protein supplement with a
high ruminal degradability.
– If forage contains a low concentrations of crude protein and a moderate
energy level (like corn stalks), then feed a protein supplement with a
high ruminal degradability.
• Ruminal degradability of protein
Dry corn
High moisture corn
Soybean meal
Expeller soybean meal (Soyplus)
Corn gluten meal
Dry corn gluten feed
Dried distillers grains
Urea
Ruminal degradability of protein, %
50
55-60
65
40
25
70
50
100
• With proper balance of RDP and RUP, dietary N can be reduced by
10 to 15% and N excretion can be reduced by 20%
– Optimal balance of degradable and undegradable protein is
dependent on the animals’ body weights (growing-finishing
cattle) or stage of lactation (dairy cows)
• In young, light-weight cattle or dairy cows in early lactation,
metabolizable protein requirements exceed the amounts of
microbial protein produced
– Therefore, feed a supplement that is high in undegraded
protein
• In feedlot cattle near finish or dairy cows in late lactation,
microbial protein is adequate for metabolizable protein
needs
– Therefore, no supplemental protein needed if degradable N
needs are met.
• Implications
– Phase feed
» Beef Feedlot
Needs
Weight range
RDP
UDP
Light (450-650 lb) High
High
Med. (650-800 lb) High
Mod.
Heavy (800-Finish) Mod.
Mod.
________Implications__________
Supplement with high RUP source
Supplement with high RDP source
(Depending of forage protein %
and degradability)
No supplemental protein for a
corn-based diet
– Example
Yearlings fed for 132 days
Diets balance for metabolizable protein and RDP requirements
Control diet
Phase feeding
13.6 % CP
12.7% CP
___________
__10.1% CP
Lb/steer
N intake
72.8
59.4
N retained in carcass
7.9
7.9
N excreted
64.9
51.5
% of excreted N volatilized
70.9
60.7
as NH3
» Lactating dairy cow
Needs
Stage of lactation RDP
UDP
Early
High
High
Mid to late
High
Mod.
Dry period
Mod.
Mod.
________Implications__________
Supplement with high RUP source
Supplement with high RDP source
(Depending on forage protein % and degradability)
Forage-based dry period diet likely
needs no protein supplementation
» Mature beef cows (Spring-calving)
Needs
Stage
RDP
UDP
Early lactation
Mod.
Mod.
Mid to late lactation Mod.
Low
Gestation
Mod.
Very low
________Implications__________
Forage-based diet usually adequate
Forage-based diet usually adequate
Forage generally meets requirements
unless low quality roughage
• Balance diets for essential amino acids by
supplementing amino acids that are protected from
ruminal degradation
– Ruminal degradation of some amino acids are protected by
binding with minerals or poorly degraded proteins
– Protected amino acids currently economically viable
• Lysine
• Methionine
– Only economically viable for lactating dairy cows
– Reduces N excretion by 13 to 20%
• Monitor protein status of cattle
– Monitor growth or milk production
– Measure milk urea nitrogen content
• Normal range, 12 -18 mg/dl
• Analyze feeds
– Frequently
• Particularly with wet feeds
– Sample appropriately
• Minimize feed losses
–
–
–
–
Check feed bunks daily
Clean bunks frequently
Adjust diets for feed intake to limit waste
Limit-feed large round bales to beef cows
• Feed losses from large round bales can be as high as 35%
• Utilize technologies to enhance incorporation of N into meat or
milk
– Implants
• Trenbolone acetate (TBA) and/or Estradiol or Zeranol
• For finishing beef cattle
• Increases daily gain 10-20%
– Primarily increases lean gain (improving N efficiency of N use)
• Increases feed efficiency 6 – 11%
– Feed additive
•
•
•
•
Ractopamine (sold for cattle as Optiflex)
Used for finishing cattle for last 28 to 42 days
Shifts energy use for fat production to protein production
Increases daily gain by 10-12% and feed efficiency by 14-20%.
– Injection
• Bovine somatotropin (sold for daily cattle as Posilac)
• Injected every 2 weeks after first 9 weeks of lactation
• Increases daily protein excretion in milk by 15%