effects of amount and profile of aa supply on mammary aa metabolism
TRANSCRIPT
Effect of amount and profile of AA supply on mammary AA metabolismDado, B.M.1; Danes, M.A.C.1 ; Broderick, G.A.2; Wattiaux, M.A.1
1University of Wisconsin, Madison; 2Broderick Nutrition & Research, LLC
Introduction
Objective
Materials and Methods
Results and Discussion
• There is room for improvement for efficiency of nitrogen use in dairy cattle
• The mammary gland (MG) synthesizes milk protein from the amino acids (AA) it takes up from the arterial blood• AA not used for protein synthesis are
catabolized, representing an inefficiency
• Assumption: milk protein is synthesized from blood AA with a high and fixed efficiency (~67%)
• However, evidence suggests efficiency is variable and dependent upon:• amount of AA supplied to the MG• possibly profile of these AA
• Change in efficiency occurs in MG metabolism through AA uptake and AA fate within the MG
• To alter arterial AA concentrations through diet manipulation and abomasal infusions
• To evaluate the effects of different amounts and profiles of AA in the arterial blood on:• mammary AA uptake from the blood• mammary AA metabolism
• 10 Holstein cows blocked by DIM into two 5x5 Latin squares
• 14-d periods• 5 treatments: 3 dietary CP levels and 2 abomasal
infusions of EAA• Blood samples collected on d14• Plasma analysis with isotope dilution and GCMS• Calculated:
• What is taken up by the MG• What is secreted in the milk protein
• Proc Mixed of SAS - 4 contrasts:
• 16%CP vs 15%CP• 15%CP vs 13.5%CP
• Individual AA responded differently to treatments• Chose to focus on Met and Leu, which represent
group1 and group 2 AA
• Arterial AA concentration, fractional removal, and mammary uptake: milk output analyzed
• Treatments were mostly effective in altering amounts and profiles of AA in arterial blood
• Mammary metabolism is specific for each AA• Greater Met supply did not increase mammary Met
uptake something else limited milk protein yield• Mammary AA uptake seems regulated more by cellular
demand than by arterial AA concentrations• MU:MO results were somewhat unexpected
• 15%CP vs 15+AA• 13.5%CP vs 13+AA
Conclusion
Arterial AA Concentration
Fractional Removal (%)
Mammary uptake: milk output
Introduction
67% Efficiency (NRC, 2001)
Mammary efficiency is variable
and dependent upon:
• Amount of AA
• Profile of AA
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PLASMA FLOW
Introduction
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• How is the change in efficiency achieved?
– Mammary gland metabolism
• AA uptake from the blood
• Fate of each AA within the mammary gland
• Manipulate to increase efficiency, but we
need more understandingmilk
ENERGYNEAA
Objective
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• Effects of different amounts and
profiles of AA in the arterial blood on:
– mammary AA uptake from the blood:
fractional removal
– mammary AA metabolism: ratio between
mammary AA uptake and milk AA output
Materials and Methods – Formulated Diets
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Formulated Diets• 60% Forage
• Soybean Meal and Canola
Meal
• Soy Hulls and High Moisture
Corn
• Vitamins and minerals
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Materials and Methods – Amino Acid Infusions
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Diets16.5% CP 15.0% CP 13.5% CP
No infusion
Infusion of:11 g/d Met11 g/d Lys5 g/d His5 g/d Leu
No infusion
Infusion of:15 g/d Met27 g/d Lys11 g/d His22 g/d Leu6 g/d Val
• AA solution prepared according to AminoCow
to provide limiting EAA in each diet
• Infused continuously into the abomasum HOME
Materials and Methods – Feeding
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4 last days of each 14-d period Split feeding into 4x/day for steady state
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Materials and Methods – Blood Sampling
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• Last day of each 14-d period
• 4x between AM and PM milking
• From coccygeal vessel and mammary vein HOME
Materials and Methods – Plasma Analysis
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Add Internal Standard Protein Precipitation Purification Evaporate NH4OH Derivatize
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Materials and Methods - Calculations
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Materials and Methods – Statistical Analysis
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• Proc Mixed of SAS
• Significance declared at P< 0.10
• Trend declared at P < 0.15
• Contrasts:
– To evaluate the effects of amounts of AA
1.16% CP vs 15% CP
2.16% CP vs 13.5% CP
– To evaluate the effects of profiles of AA
3.15% CP vs 15% CP + EAA
4.13.5% CP vs 13.5% CP + EAA
Results and Discussion
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15.6 14.5+AA 14.5 13.2+AA 13.2CP, % DM 15.6 14.5 14.5 13.2 13.2DMI, kg/d 23.2 22.6 23.7 23.8 23MP, % DM 9.5 9.1 9.1 8.4 8.4
MP and AA supply (g/d)MP 2201 2094 2162 2084 1934Met 42 51 42 55 38Lys 146 150 145 160 130His 45 47 44 51 39Leu 192 187 191 199 174Val 124 118 123 120 112
AA supply (%MP)Met 1.9% 2.4% 1.9% 2.6% 2.0%Lys 6.6% 7.2% 6.7% 7.7% 6.7%His 2.0% 2.2% 2.0% 2.4% 2.0%Leu 8.7% 8.9% 8.8% 9.5% 9.0%Val 5.6% 5.6% 5.7% 5.8% 5.8%
Lys/Met 3.48 2.94 3.45 2.91 3.42
• Actual CP content vs. expected
• NRC estimates for metabolizable
protein (MP) and AA in each treatment
• CP levels mainly changed amount of
MP (thus amount of AA) supplied to
animal
• Infusions mainly changed profile of AA
• Ideal ratio Lys:Met of 3
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Results and Discussion
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• Individual AA responded differently to the treatments
• Two AA were chosen to be discussed
– Methionine (Met)
•group 1: metabolized in the liver and not in the MG
•usually the most limiting AA in dairy rations
– Leucine (Leu)
•group 2: metabolized in the MG and not in the liver
•highest % of milk protein (19.5% of EAA)
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Results and Discussion – Arterial AA Concentrations
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15.6 14.5+AA 14.5 13.2+AA 13.20
10
20
30
40
50
60
26
38
23
49
24
Methionine (uM)
15.6 14.5+AA 14.5 13.2+AA 13.295
100
105
110
115
120
125 123
104110
120
108
Leucine (uM)
16% CP vs 15% CP P > 0.20
16% CP vs 13.5% CP P > 0.20
15% CP vs 15% CP + EAA P < 0.01
13.5% CP vs 13.5% CP + EAA P < 0.01
16% CP vs 15% CP P < 0.10
16% CP vs 13.5% CP P < 0.05
15% CP vs 15% CP + EAA P > 0.20
13.5% CP vs 13.5% CP + EAA P < 0.15
Met, g/d 15.6 14.5+AA 14.5 13.2+AA 13.2Diet 42 40 42 40 38Infusion 0 11 0 15 0Total 42 51 42 55 38
Leu, g/d 15.6 14.5+AA 14.5 13.2+AA 13.2
Diet 192 182 191 177 174Infusion 0 5 0 22 0Total 192 187 191 199 174
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Results and Discussion – Fractional Removal
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Mammary gland AA
uptake as a
proportion of AA
arterial concentration
15.6 14.5+AA 14.5 13.2+AA 13.205
101520253035404550
Met fractional removal (%)
15.6 14.5+AA 14.5 13.2+AA 13.205
101520253035404550
Leu fractional removal (%)
16% CP vs 15% CP P > 0.20
16% CP vs 13.5% CP P > 0.20
15% CP vs 15% CP + EAA P < 0.01
13.5% CP vs 13.5% CP + EAA P < 0.01
16% CP vs 15% CP P > 0.20
16% CP vs 13.5% CP P > 0.20
15% CP vs 15% CP + EAA P > 0.20
13.5% CP vs 13.5% CP + EAA P > 0.20
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Results and Discussion – Mammary Uptake: Milk Output
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Met: group 1metabolized in the liver
Leu: group 2metabolized in the MG
16%CP 15%CP+EAA 15%CP 13.5%CP+EAA 13.5%CP0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
MU:MO for Met
16%CP 15%CP+EAA 15%CP 13.5%CP+EAA 13.5%CP0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
MU:MO for Leu
16% CP vs 15% CP P < 0.1016% CP vs 13.5% CP P < 0.05
15% CP vs 15% CP + EAA P > 0.2013.5% CP vs 13.5% CP + EAA P > 0.20
16% CP vs 15% CP P > 0.2016% CP vs 13.5% CP P > 0.20
15% CP vs 15% CP + EAA P > 0.2013.5% CP vs 13.5% CP + EAA P > 0.20
Conclusion
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• Treatments were mostly effective in altering amounts and profiles of AA in arterial
blood
• Mammary metabolism is specific for each AA: concerns about treating them as a
single entity (MP)
• Greater Met supply did not increase mammary Met uptake, suggesting something
else limited milk protein yield
• Mammary AA uptake seems to be regulated more by the cellular demand than by the
arterial AA concentrations
• MU:MO results were somewhat unexpected: possible methodology limitation