This document discusses managing dietary phosphorus in dairy cattle to reduce phosphorus pollution. It notes that phosphorus intake is directly related to phosphorus excretion in manure. A study in Virginia found that reducing dietary phosphorus levels in dairy rations by 5-15% through nutritionist guidance and incentive payments lowered the amount of phosphorus being fed to and excreted by dairy cows on farms. The challenges of reducing phosphorus include the high phosphorus content of common byproducts like distillers grains and needing more information on the availability of organic phosphorus from feed sources.

1. 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

2. Nutrient concentration Specialization Nutrient Importation Nutrient Concentration Ground and Surface Water

3. Sources of nutrients Smith & Alexander, 2000

4. 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

5. Does diet matter?

6. 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

7. Why overfeed? Uncertainty about requirements - What’s the “bare minimum”? Marketing Link to reproduction? Bad habits Undetected variation in feed P, “problem feeds”

8. Phosphorus Dietary requirement

9. 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

10. “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.”

11. “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?”

12. “(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.”

13. Precision Phosphorus Feeding for Virginia Dairy Farms

14. 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

15. 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?

16. 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

17. 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.”

18. 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.

19. The distillers grain challenge

20. 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

22. “If it was easy, everyone would do it.”

23. 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

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

27. Huffard dairy General manure & crop management Impact of dietary changes on manure P Outlook for future, concerns and opportunities

28. In the real world… 0.49% 0.40% < 0.4% Dietary P:

29. 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 .