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What Dairy Cows are FedImpacts Manure Chemistry
and the Environment
J. Mark Powell and Glen A. BroderickUSDA-ARS
US Dairy Forage Research CenterMadison, WI
Waste-to-Worth ConferenceDenver, COApril 4, 2013
USDA
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Why this Research?
Manure management had been included in two legislative initiatives of USEPA
(1) Clean Water Act Abate phosphorus (P) loss in runoff from agricultural land
(focus on manure P management)
(2) Clean Air Act Abate ammonia from animal agriculture
Animal agriculture implicated in global climate change
(focus on CO2, CH4 and N2O)
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Researchsummary
points
•Dairy nutritionists evaluate dietary impacts on cows
•Soil scientists evaluate dietary impacts on manure chemistry and the environment
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•All diets are representative of what is fed on commercial dairy farms in Wisconsin
•Very few of the tested diets had any significant impacts on milk production
(just on manure and the environment)
Researchsummary
points
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Manure Nutrients and the Environment
Nutrient Environmental Implication
Phosphorus Runoff (Clean Water Act)
Nitrogen Leaching (Clean Water Act)Ammonia volatilization (Clean Air Act)Denitrification (Global Climate Change)
Carbon Methane emissions (Global Climate Change)Soil CO2 flux (Global Climate Change)
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ChronologyDairy Nutrition – Environmental Research
Research periods
2000 2003 2006 2012
Dietary Phosphorus
Dietary CP and Forages
2009
NH3
loss
Soil C and N transformations,plant response
Diet CP-MUN-UUNNH3 and N2O emissions
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Forage45 - 65%
Grain20-30%
Protein Suppl.20-30%
Minerals &Vitamins
1-2%
Manure65-80%
Milk20-35%
Typical Lactating Dairy Cow Diet
Feed protein and phosphorus conversion efficiency
Typical Lactating Cow Rations & Conversion Efficiencies
(confinement dairy)
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Some dairy ration impacts on manure chemistry
Phosphorus
Fecal PFecal soluble P
NitrogenFecal N: Urinary N ratio
Fecal endogenous N Fecal fiber N
Urinary urea N
CarbonFecal structural CHO
Fecal Non-structural CHO
Forage
Grain
Protein Suppl.
MineralsVitamins
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Phosphorus
• Fecal P excretions• Manure land spreading • Soil test P (Bray-1)• Runoff P
Minerals
The dietary P story (A response to water quality
legislation)
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Ration P above NRC recommended level (0.35%) is excreted as water-soluble P in feces
P e
xcre
tion
in f
eces
(g/
cow
/d) insoluble-P soluble-P
Ration P (% DMI)
Satter et al., 2005
Requirement
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…..which increases runoff of water-soluble P after manure application (no-till corn silage)
0
20
40
60
80
100
0.32%
0.48%
Spring application
Fallapplication
DR
P l
oad
(g
/ha)
b b
a
a
Ebeling et al., 2002
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…..which increases the cropland requirementfor manure P spreading
(P-based regulations)
Acres
Ration P (%)
Powell et al., 2004
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-5
0
5
10
15
20
25
0.35I
0.55I
0.38I
0.48I
0
1.25
2.50
Annual Increase in Bray-1 P (ppm)
Ration P (%)
…..and increases soil-test P levels(N-based management)
Powell et al., 2004
Manure P in excess of crop needs (kg/ha)
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Nitrogen and the
Environment
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Impacts of ration
CP level and CP forms
• Fecal N: Urinary N ratio• Urinary urea N• Ammonia emissions • Nitrous oxide emissions• Fecal N mineralization in
soil• Plant N uptake
The dietary CP story
(A response to air quality legislationand global climate change)
Protein Suppl.
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Castillo et al., 2000
Excessive CP in rations reduces CP use efficiency and increases urine N
excretion
Castillo et al., 2000
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13.6% CP
19.4% CP
Manure Ng/cow/d
222 314
% Urine N 52 68
% Fecal N 48 32
Excess ration CP increases manure N
and urine N excretions
a
ab
b
….and also ammonia emissionsafter manure land application
% o
f m
anu
re
N l
ost
as
amm
on
ia
Manure type
Misselbrook et al., 2005
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TRADEOFFSRation CP impacts ammonia lossbut also manure N availability to plants
Powell et al., 2011
LP HP
So
il in
org
anic
N
After cessation of NH3 volatilization (48h)
Slurry
Powell et al., 2006
-120-100-80-60-40-20
0204060
0 100 200 300 400
HP LP
Net so
il I
N (
mg k
g-1
)
Days after feces application to soil
Y=-15.8+0.57x-0.002x2 R2 =0.77
Y=-49.2+0.18x-0.0009x2 R2 =0.91
LP
HP
So
il in
org
anic
N
Feces
Day after application to soil
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0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
LCP HCP
0
5
10
15
20
25
b
a
b
a
b
Oat DM Oat N
N u
pta
ke (
mg
pot-
1)
DM
yie
ld (
g p
ot-
1)LP HP
0
0.2
0.4
0.6
0.8
1.0
1.6
1.2
1.4
0
5
10
15
20
25
Powell et al., 2006
……and crop yield and N uptake
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Dairy cow component
Ammonia Amino acids
Liver
Bloodstream (BUN)
Urea
Udder Kidney
MUN UUN
Dietary Nitrogen
Urea
Rumen Intestine
Post UUN excretion components
NH4+ NO3
-
NH3N2O
NO3-NH4
+
(barns, manure storage, soils)
RelationshipsDietary N,
Milk urea N, Urinary Urea N
andNH3 and N2Oemissions
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Relationships Dietary CP, MUN, UUN
UUN = 16.2 * MUN - 34.2R² = 0.79
100
120
140
160
180
200
220
240
8 10 12 14 16 18MUN (mg/100mL)
UU
N e
xcre
tion
(g/c
ow p
er d
ay)
I154
I166
I178
I190
I201
Ration CP (g/kg) a
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Distribution of milk urea N (MUN)197 herds, 37,800 cows
WisconsinP
erc
en
t o
f a
ll c
ow
s
≤10 11-12 13-14 15-16 >16
0
5
10
15
20
25
30
MUN (mg/100mL)
53% to 73% overfed dietary CP}Desirable MUN
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Use MUN as management toolto minimize dietary N, UUN excretion
NH3 and N2O emissions
0
30
60
90
120
150
180
10 11 12 13 14 15 16
- 3
- 6
MUN (mg/100mL)
NH3-N N2O-N
- 9
Dai
ly U
UN
loss
as
NH
3 –N
and
N2O
-N(g
/cow
)
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• NH3 emissions by 35 to 42%
• N2O emissions by 18 to 21%
On Wisconsin dairy farms
feeding balanced rations for MUN concentrations
of 12 to 10 mg/dL
would reduce
Per
cen
t o
f al
l co
ws
≤10 11-12 13-14 15-16 >16
0
5
10
15
20
25
30
MUN (mg/100mL)
53% to 73% overfed dietary CP}Desirable MUN
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Forage
• Fecal endogenous N excretion
• Fecal fiber N excretion • Mineralization of fecal N in
soil• Plant N uptake of fecal N
The forage story (Enhanced energy & protein use
efficiency)
Forage
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Feed components
NDIN (%)
C:N
CS LP 8.3 15.5
CS HP 6.4 14.8
AS LP 4.8 18.3
AS HP 5.3 18.1
Powell et al., 2006
Forage type in dairy ration impacts C:N ratio in manure, manure N mineralization,
crop N availability and crop yield
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Silage type impacts fecal N mineralization in soil
Days of feces incubation in soil
|100
|200
|300
|400
a
bb
Oat DM Oat N
CS AS
DM
yie
ld (
g/p
ot)
0
0.5
1.0
1.5
2.0
2.5
3.0
N u
pta
ke (
mg
/po
t)
0
5
10
15
20
25
a
b
3.5
….which impacts crop production and N uptake
Powell et al., 2006
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12 14 16 18 200
10
20
30
40
50
60
f(x) = − 3.96611418047882 x + 106.58861878453R² = 0.652978528959628
Carbon/Nitrogen ratio in dairy feces
Oat
N u
pta
ke
(% a
pp
lied
fec
al N
)
Forage type in dairy ration impacts C:N ratio in manure, manure N mineralization,
crop N availability and crop yield
Powell et al., 2006
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Forage tannins reduce urine N excretion
Alf BF-T-Low
BF-T-High
Manure Ng/cow/h
12.3 15.8 17.1
% Urine N
55 60 40
% Fecal N
45 40 60
….and ammonia emissionsafter manure land application
0
5
10
15
20
25
30
35
Fresh manure Stored manure
% m
anur
e N
lost
as
amm
onia
a a
b bc
a
Misselbrook et al., 2005
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Feces (Organic N)
+Urine (urea N)
NH3 solNH4 sol
NH3 gas
ureaseenzymes
Mineralization
Dietary Tannins Decrease Urease Activity in Dairy Feces
0
2
4
6
8
10
12
0 3 6 9 1215182124273033363942454851
0T LT MT HT
NH 3
-N (m
g)
**
*
1 3 6 12 24 36 48
*
Time after dairy slurry application (h) Powell et al., 2011
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SummaryRation Impacts
• Minerals, protein supplements and forages impact manure P, N and C excretions, and their transformations in water, air and soil
• Dietary P can be monitored using fecal P
• Dietary N can be monitored using MUN
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SummaryRation Impacts
•Dairy rations can be formulated to satisfy the nutrition requirements of healthy, high producing cows while producing excreta less susceptible to environmental loss
•These are win-win strategies that enhance feed use (and in most cases reduces costs) and environmental impacts of dairy production