Perspectives in ruminant Urea recycling protein efficiency, - - PowerPoint PPT Presentation

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Perspectives in ruminant Urea recycling protein efficiency, - - PowerPoint PPT Presentation

Topics for today Perspectives in ruminant Urea recycling protein efficiency, recycling, Should I add urea to the diet? and amino acids Amino acid requirements Evan Titgemeyer Should be believe the NRC? Kansas State University Decreasing


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SLIDE 1

Perspectives in ruminant protein efficiency, recycling, and amino acids

Evan Titgemeyer Kansas State University Topics for today

Urea recycling Should I add urea to the diet? Amino acid requirements Should be believe the NRC?

Decreasing dietary CP

Reproduction, diet cost, environment Still meet MP requirement?

  • Increase RUP
  • Supplement AA

But, are the bacterial happy?

Predicting RDP requirements

Estimate MCP (microbial protein) Estimate efficiency of N capture RAN requirement = MCP ÷ efficiency RAN supply = RDP + recycled urea

(MCP = Microbial Crude Protein) (RAN = Ruminally Available N)

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SLIDE 2

Kennedy, 1980 Rumen ammonia, mg/L Ruminal clearance of urea (L/day) With sucrose Without sucrose

Ruminal Clearance of Urea

Urea Urea VFA (pH 6.2-6.6) NH3

+

  • Urease

NH3 Urea movement across epithelium

Serosa Mucosa

Urea Urea NH3 NH3

Serosa Mucosa

MCP Urease NH3

Urea supplementation (% of DM) 0.4 0.8 Diet CP, % 12.6 13.7 14.9 DMI, kg/d 18.1 18.9 19.0 Milk, kg/d 32.7 33.8 34.0 Milk protein, kg/d 0.90 0.94 0.96 Rumen NH3, mM 3.8 6.2 8.2 PUN, mM 3.3 5.5 7.8 Lactating dairy cattle

Rojen et al., 2011

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SLIDE 3

Urea supplementation (% of DM) Nitrogen 0.4 0.8 N Intake, g/d 366 416 457 Urea Production, g/d 113 174 186 Recycled, g/d 75 104 96 Salivary, g/d 11 16 Recycled, % 66 60 52 Lactating dairy cattle

Rojen et al., 2011

Urea = 113 Liver Diet RDP = 240 75

Rojen et al., 2011

Dairy cows fed 12.6% CP diet Urine = 27 NH3 = 105 ??

Saliva = 11

How do we use this information?

Target optimal supply of RAN: ‐ If we know MCP and ruminally recycled urea, then we can calculate the necessary RDP My perspective: ‐ For most lactation diets, deficiencies in RAN are unlikely to exist and certainly not likely to be severe

MP Requirements

‐ NRC (2001) MP requirement = maintenance + milk protein/0.67 ‐ Estimate of efficiency is key! ‐ Efficiency < 0.67 ‐ Efficiency not constant, at least for a herd

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SLIDE 4

Amino acid utilization

Input Output

‐2 ‐1 1 2 3 4 2 4 6 8 10 12

NRC

MP Requirements

NRC, 2001 40 50 60 70 80 90 200 400 600

Milk N Productive N Efficiency = 64% 42% 23% 15%

Casein supplementation, g/d Nitrogen, g/d

Efficiency of MP use in lactating cows

Whitelaw et al., 1986

Efficiency of nutrient use (Individuals vs. herds)

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SLIDE 5

Plasma Lysine

16 20 24 28 32 20 30 40 50 60 70 80 90 100 110

3 6 9 12 15

Nitrogen Retention

Lysine supplementation, g/d

Lesser affinity Greater affinity

AA Requirements

Efficiency of AA use isn’t static ‐ Energy effects ‐ AA role as anabolic stimulus

16 18 20 22 24 26 1 2 3

N retention, g/d Effect of Energy Supply on Methionine Use Supplemental L-Methionine, g/d Schroeder et al., 2006

Efficiency = 11% +Glucose Control +Fat +Propionate +Acetate Efficiency = 21%

75 100 125 150 175 200 225 250 150 300 450 600 750

Low energy intake High energy intake Amino acid supply, g/d Milk protein secretion

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SLIDE 6

MP Requirements

‐ Estimates of maintenance and efficiency are correlated with each other

Input Output

‐2 ‐1 1 2 3 4 2 4 6 8 10 12

NRC Reality

Efficiency of use varies among AA

Average efficiency of AA utilization for growth ‐ Methionine = 26% (11 trials) ‐ Leucine = 38% (4 trials) ‐ Histidine = 64% (2 trials) ‐ Lysine = 47% (3 trials)

AA Requirements

Why hasn’t the 0.67 efficiency ruined the dairy industry? ‐ No one uses it as gospel ‐ Overestimated maintenance requirement balances the underestimated efficiency ‐ MP supply correlated to energy supply ‐ We work over a fairly narrow range

AA Requirements

We have a lot to learn! ‐ Empirical observations of responses to methionine and lysine are useful in predicting times to supplement ‐ At some point, perhaps in 10‐15 years, we’ll have answers on some other amino acids