Dietary nutrient management:

What goes in, must come out.

Dr. Katharine Knowlton, Dep’t of Dairy Science, Virginia Tech

Jimmy Huffard, Huffard Dairy Farm, Crockett VA

Nutrient concentration

• Specialization

• Nutrient Importation

• Nutrient Concentration

• Ground and Surface Water

Sources of nutrients

Smith & Alexander, 2000

Soil P accumulation

• Phosphorus• Manure N and P in

imbalance

• Manure application to meet N needs = excess P

• P accumulates

• P can runoff from saturated soil, even without erosion

• Contaminates surface water

Low4%

Med

8%

High22%

Very

High66%

Soil test P in Rockingham county, VA, ‘07-10

Does diet matter?

P intake and excretion

• Relationship between P intake and excretion?

• 13 early-lactation cows

• Fed diets containing one of 3 levels of dietary P

• Days 7-75 of lactation

• Total collection study (milk, urine, feces)

• Direct, linear relationship between P intake and excretion

0.34% 0.52% 0.67%0

20

40

60

80

100

120

Dietary P content

P e

xcre

tion

, g/d

Knowlton et al., 2002

Why overfeed?

• Uncertainty about requirements - What’s the “bare minimum”?

• Marketing

• Link to reproduction?

• Bad habits

• Undetected variation in feed P, “problem feeds”

Survey says???

• Survey of dairy nutritionists across US

• Independent & company affiliated

• 131 respondents

• Range from 1 client to 150

• From 200 cows to 95,000

1 2 3 4 5 6 7 8 9 100

5

10

15

20

25

30

35

3

9 8 8

24

9

23

29

107

On a scale of 1 to 10 (10 being the most important), is balancing for ration P a

priority?

53% say ‘yes, a priority’

“Energy balance is more critical to reproductive success than "over-loading" P to replace heat detection management. “

“I work close to the Bay, so I constantly monitor the P levels in my diets.”

“Clients are being regulated with nutrient management plans, so it is a priority, but ration cost dictates the use of higher levels of byproduct feed that contain more P.”

“P requirements are met or exceeded by natural sources in almost all cases. We do not address excesses unless nutrient management plans dictate.”

Adequate

Too low

Too high

Do you feel the current NRC recommenda-tion of P for lactating cows is:

“Most of the problem is with availability data”

“I feed at NRC recommendations and production, health and reproduction among the 25,000 cows I serve is excellent.”

“I am very confident that the 0,31% P requirement was well researched. Dr. Larry Satter's group at USDA Dairy Forage center did good work looking at bone strength with 0.31 P diets in lactating first calf heifers, the class of animal with the greatest P requirements.”

“Why is Germany's bioavailability correct at 80% when the 1989 NRC used a lower figure?”

“Slightly high”

“Only a tad low”

Higher; 1%

Lower; 99%

Have you changed your recommenda-tions for dietary P content over the last 3

to 5 years?

“Public perceptions of animal agriculture & CAFO's may prevent future expansion of many dairy farms. If we’re not proactive , we’ll be seen as "hiding" poor practices.”

“I changed because of research showing we did not need to supplement as much.”

“(Our company) has recommended lower P levels for years and I always try to keep at the low end.”

“I reduced my recommendations because of

manure management concerns and how feeding management can impact P

levels in manure.”

“The mindset of vets and educators has changed allowing us to run lower P levels.”

Precision Phosphorus Feeding for Virginia Dairy Farms

Components

• Feed sampling, analysis, bimonthly 3 years

• Calculate P requirements, P intake

• Incentive payments based on ( intake / req’t )

• $12 / $6 / $3 per cow per year

• Payment capped at 400 cows

• No penalty for overfeeding

Did it work?

• 215 herds

• Each year, more farms succeeded in reducing dietary P to receive incentive payment

• P feeding down by ~5-15%

• Next steps?Year 1 Year 2 Year 3

0102030405060708090

100

% o

f fa

rms

re

ce

ivin

g i

nc

en

tiv

e

pa

ym

en

t

Survey says???

• Survey of dairy nutritionists across US

• Independent & company affiliated

• 131 respondents

• Range from 1 client to 150

• From 200 cows to 95,000

“Price is easy - the problem is trusting the P value on Soy, DD, Wheat, Brew etc.”

“Sometimes higher P feeds, like distillers dried grains, are cost effective feeds. Hence, overfeeding P may be more economical than keeping P at NRC 2001 levels.”

“We need new research considering the availability of organic P.”

“P availability????”

“I sample, so content is not a worry. The biggest problem is that low cost byproducts like DDG have too much P.”

The most challenging aspect of reducing dietary P?

Uncertainty in ration ingredients

Cost

Uncertainty of P content of feedstuffs

0% 20% 40% 60%

More documentation that current NRC recommendations for P are adequate

Updated requirements for maintenance, production and reproduction

Availability of P from different sources

0% 20% 40% 60% 80%

“Not all software programs are "current"

and I question myself on how low is too low.”

Adequate data and field experience exist. Train people. Or do a P tax like Netherlands.

“I think current NRC recommendations are adequate. The biggest thing is making sure our feedstuffs have the true amounts and that they are available to the animals.”

What about new and well designed research?

Need to work on true bioavailability of P in feedstuffs

What new information do you need?

The distillers grain challenge

Organic P availability?

• Endogenous phytase activity is affected by diet.

• Phytate escape from rumen

• Heat treated grains

• High rate of passage

• High organic P100% hay

55% barley

90% barley

0

2

4

6

8

10

12

14

16

18

Pi r

elea

se, u

g/m

l RF

/min

Yanke et al., 1998

487*

483

57*

34*8* 5*

82*

1* 25*7*8* 32*

64*

222330

8*

53*Rumen

Salivation

Blood

DietPi

PiPm

Pi

Small Intestine

Pi

Large Intestine

Pm

Feces

Pi

Bone

Pi

Urine

PT

Milk

PT

Po

Po

Po

Po

Pp

Pp

Pp

Pp

Pp

Pi

0

4*

19*

Po

14*

52*

2

0*

0

“If it was easy, everyone would do

it.”

Virginia regulations

• Virginia Pollution Abatement permit• CAFO is > 300 animal units, liquid manure storage

• P-based nutrient mgmt planning since 2007

• Storage required, no discharge to surface water• 120-150 days manure storage

• Annual inspections of permitted facilities

• Farm in the family for >200 years• Jerseys arrived in 1929• 350 milking cows, plus 360 heifers• Milk 2X

Huffard dairy

• General manure & crop management• Impact of dietary changes on manure P• Outlook for future, concerns and opportunities

In the real world…

1994

1996

1998

2000

2002

2004

2006

2008

2010

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

Spring

Fall

Ma

nu

re P

, %

of

DM

0.49% 0.40% < 0.4%Dietary P:

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S.D.A., Award No. 2009-55206-05267 .