How Low Can We Go: Nitrogen in Dairy Rations- Mike Van Amburgh


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Mike Van Amburgh presented this material during DAIReXNET's March 7, 2011 webinar on nitrogen in dairy rations. He discussed how low we can formulate nitrogen in rations, as well as what this means for the cost of the ration and for environmental impact.

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  • This material was presented as part of DAIReXNET’s March 7, 2011 webinar entitled 'How Low Can We Go: Nitrogen in Dairy Rations'. The recorded versions of all of our webinars are located at
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How Low Can We Go: Nitrogen in Dairy Rations- Mike Van Amburgh

  1. 1. Protein Formulation for High Producing Lactating Dairy Cattle: What are our practical limits?<br />Mike Van Amburgh<br />Department of Animal Science<br />
  2. 2. Outline<br /><ul><li>What are the efficiencies of nitrogen utilization </li></ul> for lactating dairy cattle and what that might<br /> mean for ration formulation<br /><ul><li>Discuss some of what we have learned about </li></ul> nitrogen metabolism<br /><ul><li>Some research studies and farm examples
  3. 3. Summary</li></li></ul><li>Improving Efficiency of Use of Intake Nitrogen<br />Opportunities exist – need refining<br />On farm N efficiencies (milk N:feed N) <br />20 to 32%<br />Theoretical efficiency limit 40 to 45% in lactating dairy cattle (Van Vuuren and Meijs, 1987; Hvelplund and Madsen, 1995)<br />Practical limit is ~ 38 to 40% (groups are achieving this)<br />Requires refinement of current ration formulation models – better balancing for rumen N and post-ruminal amino acids<br />Requires refinement of feeding management – reduce variation associated with feed, management<br />
  4. 4. Improving Efficiency of Nitrogen Use<br />Milk protein output is a function of energy supply and amino acid balance<br />Urine N is variable and is a function of excess nitrogen intake and recycling<br />Urine N is most volatile form – so reducing it will reduce the environmental impact and improve efficiency<br />High levels of urinary indicate:<br />Overfeeding total protein<br />High rumen N balance relative to microbial demand<br />Can use monitoring tools like milk urea nitrogen to diagnose independent of production responses<br />
  5. 5. Value of the “Safety Factor”<br />500 cows <br />With forage availability, ration can be balanced at 15% CP for level of production (85 lbs/d, 52.5 lb DMI)<br />Nutritionist level decision – “safety factor” – doesn’t want cows to lose milk, doesn’t want to lose customer<br />Management considerations - variation<br />Cost of 15% vs 15.5% in SBM equiv. ~1 lb = $0.20/cow/d or $36,500/year<br />
  6. 6. Impacts of source and amounts of CP on intestinal supply of N and performance of cows<br />Ipharraguerre and Clark, 2005<br />
  7. 7. Urinary N is variable form of excreted N Fecal N is fairly constant<br />
  8. 8. Nitrogen excretion in milk, feces and urine based on N intake in lactating dairy cattle – under controlled conditions of energy as first limiting: 88 lb milk/d @53 lb DMI range in CP intake 14 to 18.7%<br />
  9. 9. CNCPS v6.1 Nutrient Excretion – Manure <br />and Manure Nitrogen<br />
  10. 10. RDP Required in Diet DM<br /><ul><li>Determined by the amount and type of fermentable carbohydrates in the diet
  11. 11. Dairy NRC (2001): 9 – 11% of diet DM
  12. 12. For diets common to the Northeast: 10.4 – 10.8%
  13. 13. Rely on feed intake and MUN to make final decision
  14. 14. MUN levels of 8 to 10 mg/dl are ideal – need to manage well
  15. 15. CNCPSv6.1 RDP levels as low as 7.6% with good performance – again need to manage well</li></li></ul><li>Blood Urea<br />Ammonia<br />N intake<br />Urinary <br />Urea<br />
  16. 16. Effect of forage preservation method on urea N production and recycling (Ouellet et al., 2004)<br />6 cows, 3x3 Latin square<br />Diets:<br />60% forage, 40% concentrate (14.5% CP) fed 12x/d<br />3 different forages:<br />Sun-cured hay, 10.1% CP<br />Formic acid-treated silage (12.0% CP)<br />Microbial inoculated silage (12.2% CP)<br />
  17. 17. Ouellet et al., 2004<br />Form of forage preservation had little effect on urea N <br />production and recycling<br />
  18. 18. Lysine and Methionine ratios<br /><ul><li>Current recommendations</li></ul>Rulquin<br /><ul><li>MET: 2.50% of metabolizable protein supply
  19. 19. LYS: 7.30% of metabolizable protein supply
  20. 20. These are similar to 2001 Dairy NRC (2.40 and 7.20%)</li></ul>Current Recommendations<br /><ul><li>MET: >2.20% of MP supply
  21. 21. LYS: >6.80% of MP supply
  22. 22. While maintaining a 3:1 ratio of LYS:MET</li></ul>With new implementation of CNCPS v6.1, factorial calculations appear more in line with ratios.<br />
  23. 23. Limiting amino acids in lactating dairy cows<br />Met, Lys, and His identified most often as first limiting (but His is questionable in US diets)<br />Met: when most RUP is provided by oilseed meals, animal-derived proteins, or a combination of the two<br />Lys: when corn or feeds of corn origin provide most or all dietary RUP<br />His: when grass silage, barley and oat diets are fed with or without feather meal as sole source of supplemental RUP <br /> Chuck Schwab<br />
  24. 24. Herd Level Examples of Improved Nitrogen Efficiency<br />
  25. 25. Example Herd A – 54 lb DMI, 92 lb Milk<br />
  26. 26. Example Herd Ingredients – 54 lb DMI, 92 lb Milk<br />
  27. 27. Example herd B - 53 lb DMI, 89 lb milk <br />
  28. 28. Example herd B - 53 lb DMI, 89 lb milk<br />
  29. 29. Herd C <br />Current stats<br />DMI 50 lb <br />CP 15.8%<br />NDF 30.2%<br />Actual milk 84 lb <br />ME allowable 83.5 lb<br />MP allowable 91 lb<br />True protein 3.1%<br />Fat 3.7%<br />Met 2.3% MP<br />Lys 6.77% MP<br />
  30. 30. Herd C <br />Concentrate mix contains Smartamine and Alimet<br />
  31. 31. Herd C<br />
  32. 32. Herd C<br />
  33. 33.
  34. 34.
  35. 35. What was the impact on N excretion?<br />Our calculations indicate ~60 g N/cow/d <br />less urinary excretion <br />1100 cows = ~26.5 tons N less in the <br />environment over 365 d lactation<br />In 2009, that was $0.40/cow/d reduced<br />feed costs<br />
  36. 36. Herd Example - D<br />1050 cows – High group characterized<br />1,542 lb BW <br />~100 DIM<br /> 59.5 lb DMI<br />15.8% CP<br />60% Forage<br />120 lb milk/d<br />Milk:Feed (Feed efficiency): 1.99<br />
  37. 37. Herd Example - D<br />NDF, %DM: 30.9<br />Starch, % DM: 28.7<br />Sugar, % DM: 5.4<br />Ether extract, % DM: 5.1<br />%Forage: 60.1<br />Forage NDF, %BW: 0.94<br />
  38. 38. Herd Example - D <br />Productive N : N Intake – 38%!<br />Remember – most farms are <br />25 to 30%<br />Productive N: Urinary N – 1.33:1<br />Most farms are 0.6 to 0.8:1<br />
  39. 39. Summary:We have the opportunity to lower protein intakes to reduce the environmental impact of dairy farms and improved income over feed costsWe are getting better at balancing at the limits of protein requirements for lactating cowsAs we approach the absolute requirement, it provides us with the opportunity to estimate the opportunity cost of feed and nutrient managementAny effort to do this will require greater intensity of management and adherence to SOP’s <br />