What We Feed Dairy Cattle Impacts Manure Chemistry and the Environment


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For more: http://www.extension.org/67674 During the last part of the 20th century, animal manure management became an environmental concern. In response to these concerns, legislation was enacted to control manure management and the emission of undesirable gasses (e.g., methane, ammonia, nitrous oxide) from animal production systems. The purpose of this paper is to illustrate how mineral phosphorus (P) supplements, forage types and amounts, and the crude protein (CP) fed to lactating cows impact manure chemistry and the fate of manure nutrients in the environment.

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What We Feed Dairy Cattle Impacts Manure Chemistry and the Environment

  1. 1. What Dairy Cows are FedImpacts Manure Chemistryand the EnvironmentJ. Mark Powell and Glen A. BroderickUSDA-ARSUS Dairy Forage Research CenterMadison, WIWaste-to-Worth ConferenceDenver, COApril 4, 2013USDA
  2. 2. Why this Research?Manure management had been includedin two legislative initiatives of USEPA(1) Clean Water ActAbate phosphorus (P) loss in runoff from agricultural land(focus on manure P management)(2) Clean Air ActAbate ammonia from animal agricultureAnimal agriculture implicatedin global climate change(focus on CO2, CH4 and N2O)
  3. 3. Researchsummarypoints•Dairy nutritionists evaluate dietaryimpacts on cows•Soil scientists evaluate dietary impacts onmanure chemistry and the environment
  4. 4. •All diets are representative of what is fedon commercial dairy farms in Wisconsin•Very few of the tested diets had anysignificant impacts on milk production(just on manure and the environment)Researchsummarypoints
  5. 5. Manure Nutrientsand the EnvironmentNutrient Environmental ImplicationPhosphorus Runoff (Clean Water Act)NitrogenLeaching (Clean Water Act)Ammonia volatilization (Clean Air Act)Denitrification (Global Climate Change)Carbon Methane emissions (Global Climate Change)Soil CO2 flux (Global Climate Change)
  6. 6. ChronologyDairy Nutrition – Environmental ResearchResearch periods2000 2003 2006 2012DietaryPhosphorusDietary CP and Forages2009NH3lossSoil C and Ntransformations,plant responseDiet CP-MUN-UUNNH3 and N2Oemissions
  7. 7. Forage45 - 65%Grain20-30%ProteinSuppl.20-30%Minerals &Vitamins1-2%Manure65-80%Milk20-35%Typical Lactating Dairy Cow DietFeed protein and phosphorusconversion efficiencyTypical Lactating Cow Rations& Conversion Efficiencies(confinement dairy)
  8. 8. Some dairy ration impactson manure chemistryPhosphorusFecal PFecal soluble PNitrogenFecal N: Urinary N ratioFecal endogenous NFecal fiber NUrinary urea NCarbonFecal structural CHOFecal Non-structural CHOForageGrainProteinSuppl.MineralsVitamins
  9. 9. Phosphorus•Fecal P excretions•Manure land spreading•Soil test P (Bray-1)•Runoff PMineralsThe dietary P story(A response to water quality legislation)
  10. 10. Ration P above NRC recommended level (0.35%)is excreted as water-soluble P in fecesPexcretioninfeces(g/cow/d) insoluble-P soluble-PRation P (% DMI)Satter et al., 2005Requirement
  11. 11. …..which increases runoff of water-soluble Pafter manure application (no-till corn silage)0204060801000.32%0.48%SpringapplicationFallapplicationDRPload(g/ha)b baaEbeling et al., 2002
  12. 12. …..which increases the cropland requirementfor manure P spreading(P-based regulations)AcresRation P (%)Powell et al., 2004
  13. 13. -505101520250.35I0.55I0.38I0.48I01.252.50Annual Increasein Bray-1 P (ppm)Ration P (%)…..and increases soil-test P levels(N-based management)Powell et al., 2004Manure P in excessof crop needs (kg/ha)
  14. 14. Nitrogenand theEnvironment
  15. 15. Impacts of rationCP level and CP forms• Fecal N: Urinary N ratio• Urinary urea N• Ammonia emissions• Nitrous oxide emissions• Fecal N mineralization in soil• Plant N uptakeThe dietary CP story(A response to air quality legislationand global climate change)ProteinSuppl.
  16. 16. Excessive CP in rations reduces CP useefficiency and increases urine N excretionCastillo et al., 2000
  17. 17. 13.6% CP 19.4% CPManure Ng/cow/d222 314% Urine N 52 68% Fecal N 48 32Excess ration CPincreases manure Nand urine N excretionsaabb….and also ammonia emissionsafter manure land application%ofmanureNlostasammoniaManure typeMisselbrook et al., 2005
  18. 18. TRADEOFFSRation CP impacts ammonia lossbut also manure N availability to plantsPowell et al., 2011LP HPSoilinorganicNAfter cessation of NH3 volatilization (48h)SlurryPowell et al., 2006-120-100-80-60-40-2002040600 100 200 300 400HP LPNetsoilIN(mgkg-1)Days after feces application to soilY=-15.8+0.57x-0.002x2 R2 =0.77Y=-49.2+0.18x-0.0009x2 R2 =0.91LPHPSoilinorganicNFecesDay after application to soil
  19. 19. HCP0510152025bababOat DM Oat NNuptake(mgpot-1)DMyield(gpot-1) LP HP00. et al., 2006……and crop yield and N uptake
  20. 20. Dairy cow componentAmmonia Amino acidsLiverBloodstream (BUN)UreaUdder KidneyMUN UUNDietary NitrogenUreaRumen IntestinePost UUN excretion componentsNH4+NO3-NH3N2ONO3-NH4+(barns, manure storage, soils)RelationshipsDietary N,Milk urea N,Urinary Urea NandNH3 and N2Oemissions
  21. 21. RelationshipsDietary CP, MUN, UUNUUN = 16.2 * MUN - 34.2R² = 0.791001201401601802002202408 10 12 14 16 18MUN (mg/100mL)UUNexcretion(g/cowperday)I154I166I178I190I201Ration CP (g/kg)a
  22. 22. Distribution of milk urea N (MUN)197 herds, 37,800 cowsWisconsinPercentofallcows≤10 11-12 13-14 15-16 >16051015202530MUN (mg/100mL)53% to 73% overfeddietary CP}Desirable MUN
  23. 23. Use MUN as management toolto minimize dietary N, UUN excretionNH3 and N2O emissions030609012015018010 11 12 13 14 15 16- 3- 6MUN (mg/100mL)NH3-N N2O-N- 9DailyUUNlossasNH3–NandN2O-N(g/cow)
  24. 24. • NH3 emissions by 35 to 42%• N2O emissions by 18 to 21%On Wisconsin dairy farmsfeeding balanced rationsfor MUN concentrationsof 12 to 10 mg/dLwould reducePercentofallcows≤10 11-12 13-14 15-16 >16051015202530MUN (mg/100mL)53% to 73% overfeddietary CP}Desirable MUN
  25. 25. Forage• Fecal endogenous N excretion• Fecal fiber N excretion• Mineralization of fecal N in soil• Plant N uptake of fecal NThe forage story(Enhanced energy & protein use efficiency)Forage
  26. 26. FeedcomponentsNDIN(%)C:NCS LP 8.3 15.5CS HP 6.4 14.8AS LP 4.8 18.3AS HP 5.3 18.1Powell et al., 2006Forage type in dairy ration impacts C:N ratioin manure, manure N mineralization,crop N availability and crop yield
  27. 27. Silage type impacts fecal Nmineralization in soilDays of feces incubation in soil|100|200|300|400abbOat DM Oat NCS ASDMyield(g/pot)….which impactscrop production and N uptakePowell et al., 2006
  28. 28. y = -3.9661x + 106.59R2 = 0.653010203040506012 14 16 18 20Carbon/Nitrogen ratio in dairy fecesOatNuptake(%appliedfecalN)Forage type in dairy ration impacts C:N ratio inmanure, manure N mineralization,crop N availability and crop yieldPowell et al., 2006
  29. 29. Forage tanninsreduce urine N excretionAlf BF-T-LowBF-T-HighManure Ng/cow/h12.3 15.8 17.1% Urine N 55 60 40% Fecal N 45 40 60….and ammonia emissionsafter manure land application05101520253035Fresh manure Stored manure%manureNlostasammoniaaabbcaMisselbrook et al., 2005
  30. 30. Feces(Organic N)+Urine (urea N)NH3 solNH4 solNH3 gasureaseenzymesMineralizationDietary TanninsDecreaseUrease Activityin Dairy Feces0246810120 3 6 9 12151821242730333639424548510T LT MT HTNH3-N(mg)***1 3 6 12 24 36 48*Time after dairy slurry application (h) Powell et al., 2011
  31. 31. SummaryRation Impacts• Minerals, protein supplements and foragesimpact manure P, N and C excretions, andtheir transformations in water, air and soil• Dietary P can be monitored using fecal P• Dietary N can be monitored using MUN
  32. 32. SummaryRation Impacts•Dairy rations can be formulated to satisfythe nutrition requirements of healthy, highproducing cows while producing excreta lesssusceptible to environmental loss•These are win-win strategies that enhancefeed use (and in most cases reduces costs) andenvironmental impacts of dairy production