Precision Feeding of Phosphorus for Dairy Farms- Katharine Knowlton

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
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
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”

Phosphorus
Dietary requirement

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

“Energy balance is more critical to reproductive success than "over-loading" P to replace heat detection management. “
53% say ‘yes, a priority’
“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.”
“I work close to the Bay, so I constantly monitor the P levels in my diets.”
“P requirements are met or exceeded by natural sources in almost all cases. We do not address excesses unless nutrient management plans dictate.”

“Slightly high”
“Only a tad low”
“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.”
“Most of the problem is with availability data”
“Why is Germany's bioavailability correct at 80% when the 1989 NRC used a lower figure?”

“(Our company) has recommended lower P levels for years and I always try to keep at the low end.”
“The mindset of vets and educators has changed allowing us to run lower P levels.”
“I reduced my recommendations because of manure management concerns and how feeding management can impact P levels in manure.”
“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.”

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?

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

The most challenging aspect of reducing dietary P?
“I sample, so content is not a worry. The biggest problem is that low cost byproducts like DDG have too much P.”
“Price is easy - the problem is trusting the P value on Soy, DD, Wheat, Brew etc.”
“P availability????”
“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.”

What new information do you need?
What about new and well designed research?
“Not all software programs are "current" and I question myself on how low is too low.”
“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.”
Need to work on true bioavailability of P in feedstuffs
Adequate data and field experience exist. Train people. Or do a P tax like Netherlands.

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 P
Yanke et al., 1998

“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…
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 .

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Precision Feeding of Phosphorus for Dairy Farms- Katharine Knowlton

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