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

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)

Researchsummary

points

•Dairy nutritionists evaluate dietary impacts on cows

•Soil scientists evaluate dietary impacts on manure chemistry and the environment

•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

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)

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

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)

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

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)

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

…..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

…..which increases the cropland requirementfor manure P spreading

(P-based regulations)

Acres

Ration P (%)

Powell et al., 2004

-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)

Nitrogen and the

Environment

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.

Castillo et al., 2000

Excessive CP in rations reduces CP use efficiency and increases urine N

excretion

Castillo et al., 2000

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

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

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

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

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

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

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

)

• 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

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

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

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

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

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

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

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

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