Slide 1: Exploring flexibilities in protein nutrition for a sustainable dairy industry
Exploring flexibilities in protein nutrition for a sustainable dairy industry Kelly Nichols, PhD August 5th, 2025 Balchem – Real Science Lecture Series
Slide 2: Acknowledgements
Acknowledgements The Nichols Lab
Slide 3: Protein nutrition intersects with sustainability concerns
Protein nutrition intersects with sustainability concerns Feces NH3 N2O Urine FEED PROTEIN MANURE N MILK PROTEIN N runoff NO3- Imported feed is the largest N input to whole-farm N balance • Approximately 2x the volume of fertilizer N Dutch dairies: Jarvis et al. 2011; The European Nitrogen Assessm
Slide 4: The “Nitrogen Crisis”: Not just a European problem
The “Nitrogen Crisis”: Not just a European problem
Slide 5: The “Nitrogen Crisis”: Not just a European problem
The “Nitrogen Crisis”: Not just a European problem Top 20 US regions with the greatest cropland N surplus Probability that groundwater systems violate nitrate regulations Pennino et al. 2020; Sci. Total Environ. 722:137661 Roy et al. 2021; Environ. Res. Lett. 16:035004
Slide 6: Protein nutrition intersects with sustainability concerns
Protein nutrition intersects with sustainability concerns Ruminants deliver efficiencies and inefficiencies with their transfer of dietary N into human-edible protein Growing emphasis on N discharge regulations and N-source air pollution is likely to continue in agriculture-intensive areas of th
Slide 7: Exploring flexibilities in protein nutrition
Exploring flexibilities in protein nutrition POST- RUMEN ABSORPTIVE POST-RUMEN FEED MANURE N PROTEIN MILK PROTEIN
Slide 8: Exploring flexibilities in protein nutrition
Exploring flexibilities in protein nutrition 1) Impact of energy source 2) Rumen N balance 3) Mammary gland amino acid metabolism
Slide 9: Exploring flexibilities in protein nutrition
Exploring flexibilities in protein nutrition 1) Impact of energy source 2) Rumen N balance 3) Mammary gland amino acid metabolism
Slide 10: Metabolizable protein efficiency is related to energy supply
Metabolizable protein efficiency is related to energy supply 20 MJ/d n = 825 10 MJ/d Energy-expensive 0 MJ/d protein synthesis -10 MJ/d -20 MJ/d Glucogenic potential of amino acids Energy-induced endocrine signaling regulates protein synthesis Metabolizable protein supply (g/d) Daniel et al. 2
Slide 11: Energy source affects the transfer of dietary N into milk N
Energy source affects the transfer of dietary N into milk N GLUCOGENIC • Starch-rich feedstuffs • Post-ruminal glucose • Ruminal propionate LIPOGENIC • Rumen-inert fat supplements (Ca-salts, saturated long-chain fatty acids) • Fiber-rich feedstuffs acetate, butyrate • Post-ruminal infusion of fat
Slide 12: Energy source affects the transfer of dietary N into milk N
Energy source affects the transfer of dietary N into milk N 28.6% GLUCOGENIC 32.3% 12% CP - fiber 12% CP - starch 24.3% 16.5% CP - fiber 16.5% CP - starch LIPOGENIC 30.5% Cantalapiedra-Hijar et al. 2014; Animal 8:275-285
Slide 13: Energy source affects the transfer of dietary N into milk N
Energy source affects the transfer of dietary N into milk N ↑ milk N efficiency with glucogenic energy 0.36 0.34 0.35 PGG < 0.01 0.32 PPT x FT = 0.07 0.34 0.30 Milk N/N Intake Milk N/N Intake 0.33 0.28 0.32 0.26 0.31 0.24 0.30 0.29 0.22 0.28 0.20 C L-C GG L-GG LG L-LG C H-C GG H-GG LG H-LG LF LP-L
Slide 14: Energy source affects the transfer of dietary N into milk N
Energy source affects the transfer of dietary N into milk N Milk N efficiency tends to ↑ with fat supplementation at low protein levels 0.36 0.34 0.35 0.342 0.32 PPT x FT = 0.07 0.34 0.30 Milk N/N Intake 0.324 Milk N/N Intake 0.33 0.28 0.32 0.31 0.307 0.307 0.26 0.24 0.30 0.29 0.22 0.28 0.20 C L-C
Slide 15: Energy type affects amino acid partitioning
Energy type affects amino acid partitioning Glucogenic energy stimulates partitioning of branched-chain AA (BCAA) towards extra-mammary peripheral tissues Lemosquet et al. 2009; J. Dairy Sci. 92:6068-6082 Nichols et al. 2016; J. Dairy Sci. 99:1145-1160 Curtis et al. 2018; J. Dairy Sci. 101:4542-45
Slide 16: Summary: Impact of energy source on protein efficiency
Summary: Impact of energy source on protein efficiency GLUCOGENIC • Stimulates milk protein yield and ↑ N efficiency • Stimulates insulin cascade re-partitioning of BCAA and energy metabolites towards extra-mammary peripheral tissues (muscle and adipose) = ↑ mammary blood flow LIPOGENIC • Positive
Slide 17: Exploring flexibilities in protein nutrition
Exploring flexibilities in protein nutrition 1) Impact of energy source 2) Rumen protein balance 3) Mammary gland amino acid metabolism
Slide 18: Refining rumen protein balance
Refining rumen protein balance Rumen protein balance: difference between maximum possible microbial protein synthesis from rumen-available N and energy Everything >0 79% of additional is excess rumen available N Urinary N, g/kg BW = excreted in urine Y = 0,22 + 0,79 X (NTREAT = 251, NEXP = 62, R
Slide 19: Refining rumen protein balance
Refining rumen protein balance Diet formulation parameters are dimensioned to achieve ruminal synchrony between protein and energy supply • Assumes N metabolism, N recycling, and N utilization are constant • Ignores contribution from endogenous N In practice, may lead to excessive safety margins
Slide 20: Refining rumen protein balance
Refining rumen protein balance Base + Met Base + Met + Urea P-value Rumen N requirement* 0.83 0.96 - CP, g/kg DM 136 146 - * Calculated based on bacterial growth depression % from CNCPS v7 estimate based on ruminal nitrogen requirements given the number of bacteria that can be produced from the fe
Slide 21: Refining rumen protein balance
Refining rumen protein balance Base + Met Base + Met + Urea P-value Rumen N requirement* 0.83 0.96 - CP, g/kg DM 136 146 - DM intake, kg/d 24.1 24.7 0.05 ≤ P < 0.10 ECM yield, kg/d 38.7 39.4 > 0.05 Milk true protein, g/kg 29.5 29.7 > 0.05 Milk true protein, kg/d 1.14 1.14 > 0.05 Higgs et al. 2023; J
Slide 22: Refining rumen protein balance
Refining rumen protein balance Base + Met Base + Met + Urea P-value Rumen N requirement* 0.83 0.96 - CP, g/kg DM 136 146 - DM intake, kg/d 24.1 24.7 0.05 ≤ P < 0.10 ECM yield, kg/d 38.7 39.4 > 0.05 Milk true protein, g/kg 29.5 29.7 > 0.05 Milk true protein, kg/d 1.14 1.14 > 0.05 Milk urea N, mg/dL 7
Slide 23: Refining rumen protein balance
Refining rumen protein balance Base + Met Base + Met + Urea P-value Rumen N requirement* 0.83 0.96 - CP, g/kg DM 136 146 - Balancing for estimated rumen N requirements by adding urea (likely) DM intake, kg/d 24.1 24.7 0.05 ≤ P < 0.10 ↑ N excretion with no positive impact on ECM yield, milk protein
Slide 24: Can we rely on endogenous urea to compensate?
Can we rely on endogenous urea to compensate? Proportion of hepatic urea output that recycles LIVER KIDNEY to the GIT ↑ as dietary CP content ↓ URINE Urea Mutsvangwa et al. 2016; J. Dairy Sci. 99:6298-6310 synthesis Chibisa and Mutsvangwa, 2013; J. Dairy Sci. 96:6550-6563 Absorbed ammonia Urea rec
Slide 25: Summary: Reconsidering rumen protein balance
Summary: Reconsidering rumen protein balance Cattle can use endogenous N to support short-term periods of ruminal N insufficiency may be able to ↓ safety margin on rumen-available N Lowering ruminal N supply is a route to reducing dietary CP content and N excretion • In practice, assess the ne
Slide 26: Exploring flexibilities in protein nutrition
Exploring flexibilities in protein nutrition 1) Impact of energy source 2) Rumen protein balance 3) Mammary gland amino acid metabolism
Slide 27: Digestible amino acid profile
Digestible amino acid profile • Microbial CP assume a fixed AA profile RUMEN • RUP this can be changed based on feed ingredients • microbial • rumen undegradable Optimizing N efficiency = aiming for RUP AA profile (RUP) that complements microbial AA flow SMALL INTESTINE But what is the compl
Slide 28: Absorbed amino acid profile affects marginal efficiency
Absorbed amino acid profile affects marginal efficiency Post-ruminal profile AA dose (g/d) Marginal Reference (infused or rumen-protected) efficiency Complete essential AA (EAA) 359 0.31 Doepel and Lapierre, 2010 J. Dairy Sci. 93:3264-3274 Complete non-EAA (NEAA) 356 0.03 EAA+NEAA 715 0.25
Slide 29: Absorbed amino acid profile affects marginal efficiency
Absorbed amino acid profile affects marginal efficiency Post-ruminal profile AA dose (g/d) Marginal Reference (infused or rumen-protected) efficiency Complete essential AA (EAA) 359 0.31 Doepel and Lapierre, 2010 J. Dairy Sci. 93:3264-3274 Complete non-EAA (NEAA) 356 0.03 EAA+NEAA 715 0.25 Complete
Slide 30: Absorbed amino acid profile affects marginal efficiency
Absorbed amino acid profile affects marginal efficiency Post-ruminal profile AA dose (g/d) Marginal Reference (infused or rumen-protected) efficiency Complete essential AA (EAA) 359 0.31 Doepel and Lapierre, 2010 J. Dairy Sci. 93:3264-3274 Complete non-EAA (NEAA) 356 0.03 EAA+NEAA 715 0.25 Complete
Slide 31: Absorbed amino acid profile affects marginal efficiency
Absorbed amino acid profile affects marginal efficiency Post-ruminal profile AA dose (g/d) Marginal Reference (infused or rumen-protected) efficiency Complete essential AA (EAA) 359 0.31 Doepel and Lapierre, 2010 J. Dairy Sci. 93:3264-3274 Complete non-EAA (NEAA) 356 0.03 EAA+NEAA 715 0.25 Complete
Slide 32: Absorbed amino acid profile affects marginal efficiency
Absorbed amino acid profile affects marginal efficiency Post-ruminal profile AA dose (g/d) Marginal Reference (infused or rumen-protected) efficiency Complete essential AA (EAA) 359 0.31 Doepel and Lapierre, 2010 J. Dairy Sci. 93:3264-3274 Complete NEAA 356 0.03 Marginal efficiency ↑ as digestible
Slide 33: Flexibility in mammary gland amino acid metabolism
Flexibility in mammary gland amino acid metabolism Milk Protein Yield 1200 b Group 1 His, Met, Phe, Trp b P < 0.01 ab 1000 a a ILV Ile, Leu, Val ALT Arg, Lys, Thr g/d 800 600 ↑ milk protein yield with 400 incomplete EAA profiles when SAL EAAC ILV Gr1+ILV Gr1+ALT group 1 AA are present Nichols et al.
Slide 34: Flexibility in mammary gland amino acid metabolism
Flexibility in mammary gland amino acid metabolism VEIN ARTERY AA UPTAKE = sequestration (irreversible loss) of AA structural TRANSFORMATION protein oxidation ~90% galactose fatty acids MILK PROTEIN
Slide 35: Mammary gland adaptation to essential AA profiles
Mammary gland adaptation to essential AA profiles Blood flow altered by changes in vasodilatory systems and intramammary metabolite and energy balance • AA deficiency and imbalance ↑ mammary blood flow 1200 1000 His deletion ↑ mammary 800 plasma flow Plasma flow, L/h 600 P-HIS = 0.05 400 200 0
Slide 36: Mammary gland adaptation to essential AA profiles
Mammary gland adaptation to essential AA profiles Blood flow altered by changes in vasodilatory systems and intramammary metabolite and energy balance • AA deficiency and imbalance ↑ mammary blood flow 1100 a 1000 ↑ plasma flow with greater 900 ab ab imbalance in EAA profile Plasma flow, L/h 8
Slide 37: Intramammary flexibility
Intramammary flexibility 1:1 >1:1 >1:1 Group 1 Ile, Leu, Val Arg, Lys, Thr Group 1 ILV NEAA ALT MAMMARY CELL PROTEIN Nichols et al. 2022; J. Dairy Sci. 105:7354-7372
Slide 38: Intramammary flexibility
Intramammary flexibility 1:1 >1:1 >1:1 Group 1 Ile, Leu, Val Arg, Lys, Thr Group 1 ILV NEAA ALT MAMMARY CELL N and carbon skeletons from PROTEIN Ile, Leu, Val Nichols et al. 2022; J. Dairy Sci. 105:7354-7372
Slide 39: Intramammary flexibility
Intramammary flexibility 1:1 >1:1 >1:1 Group 1 Ile, Leu, Val Arg, Lys, Thr Group 1 ILV NEAA ALT MAMMARY CELL N and carbon skeletons from PROTEIN Arg, Lys, Thr Nichols et al. 2022; J. Dairy Sci. 105:7354-7372
Slide 40: Summary: Mammary amino acid metabolism
Summary: Mammary amino acid metabolism The profile of digestible AA will impact the efficiency of use of dietary protein sources • Look for ingredient profiles that enrich digestible protein with EAA that more closely match the AA profile of casein Intramammary compensation for N and carbon betw
Slide 41: Harnessing flexibility: Take-home messages
Harnessing flexibility: Take-home messages Energy source matters with respect to improving protein efficiency • Glucogenic and lipogenic energy elicit different effects on postabsorptive AA metabolism but both can improve N efficiency Minimize rumen degradable protein balance • Can achieve moder
Slide 42: UC Davis
UCDAVIS