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Fatty acid metabolism and
milk fat depressionJennifer Stamey and Benjamin Corl
VSFA Conference and Nutritional Management “Cow” CollegeFebruary 18, 2011
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Milk Fat
• Fat is the major energy component of milk– Economic value– Physical and manufacturing properties
• Milk fat content is markedly affected by diet– High grain– Vegetable oils– Marine oils
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Fatty Acids
• Long carbon chains that contain a methyl group (CH3) at one end and a carboxyl group (COOH) at the other
• Fatty acids make lipids energy rich
• Characterized by:– Number of carbons
• Chain length– Number of double bonds
• Degree of unsaturation– Location and orientation of these bonds
• Non‐conjugated, conjugated, cis, trans
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Nomenclature and Structure
Saturated – single bonds
Unsaturated – double bonds
C C CC CC C
C C CC CC C
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CCC
H
C
H H
H HH
trans
CC
H H
C
H
HC
H
H
cis
Nomenclature and Structure
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conjugated
CC
H H
C
H
C
H
non‐conjugated
H H
C CC
H H
C
H
CH
Nomenclature and Structure
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Lipids
Free fatty acids
Hydrolysis
OH
OH
OH
H2OBacterial lipases
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Biohydrogenation
Linoleic acid(cis‐9, cis‐12 18:2)
trans‐10, cis‐12 CLA
trans‐10 18:1
Stearic acid (18:0)
Rumenic acid(cis‐9, trans‐11 CLA)
Vaccenic acid(trans‐11 18:1)
Stearic acid (18:0)
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Biohydrogenation
Linolenic acid(cis‐9, cis‐12, cis‐15 18:3)
cis‐9, trans‐11, cis‐15 18:3
trans‐11, cis‐15 18:2
trans‐15 or cis‐15 18:1 Vaccenic acid(trans‐11 18:1)
Stearic acid (18:0)
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Rumen Biohydrogenation
Unique conjugated linoleic acid (CLA)
isomers
Stearic Acid C18:0
Linolenic Acidcis‐9, cis‐12, cis‐15 C18:3
Linoleic Acidcis‐9, cis‐12 C18:2
trans‐11, cis‐15 C18:2
trans‐15 or cis‐15 C18:1 trans‐11 C18:1
cis‐9, trans‐11, cis‐15 C18:3 cis‐9, trans‐11 CLA
Numerous trans‐18:1 isomers
altered fermentation
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Fat Digestion in the Rumen
Rumen
Inert fats
TG
Glycolipids
TG or FFA
Glycerol and VFAs
FFAs
TG or FFA
Hydrolysis Biohydrogenation
transFFAs
FFAs
MicrobesPL
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Rumen Biohydrogenation Pathways
Unsaturated FA
Trans intermediates
Saturated FA
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Polyunsaturated fatty acid losses
Loor et al. (2004)
0
50
100
150
200
250
Linoleic Acid Stearic Acid
g/d
ConsumedDuodenum
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Major Fatty Acids in Milk FatFatty Acid % (weight basis) Common Name
4:0 4 Butyric6:0 3 Caproic8:0 2 Caprylic10:0 3 Capric12:0 4 Lauric14:0 11 Myristic16:0 29 Palmitic16:1 2 Palmitoleic18:0 12 Stearic18:1 25 Oleic18:2 2 Linoleic18:3 1 Linolenic
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Triglyceride Synthesis
• 98% of milk fat is triglcyeride
• Glycerol backbone with 3 ester‐linked FA
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Basal membrane ER‐membrane Apical membrane
LPL DGAT
ACC FAS
FA synthesis de novo (C4 ‐ C16)
TAG
synthesis
Glycerol
Glucose
SFA (C16 ‐ C18)
Synthesis Secretion
Acetate
ßHBA
VLDL
TAG
Glycerol
Glucose
Circulation Translocation
UFA
DesaturaseGPAT
FABP
Milk Fat Synthesis
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Major Fatty Acids in Milk FatFatty Acid % (weight basis) Fatty Acid Source
4:0 46:0 38:0 2
De novo synthesis10:0 312:0 414:0 1116:0 29
De novo and preformed16:1 218:0 1218:1 25 Uptake of preformed18:2 2
18:3 1
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Factors Influencing Milk Fat
Nutritional Factors
• Dietary fiber• Specific feeds• Feeding strategy• Ionophores
Non‐nutritional Factors
• Genetics• Stage of lactation• Season• Parity• Ambient temperature
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Milk Fat Depression in the Dairy Cow
• Recognized by Boussingault in 1845
• Naturally occurs with certain diets
• Milk fat reduced but milk yield and other components unaffected
Boussingault
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Milk Fat Depression Characteristics
• Diet‐induced– High concentrate, low fiber– Low in effective fiber– Plant and marine oil supplements– Unsaturated fatty acids
• Specific for milk fat, up to 50% decrease
• Decreased yield of all fatty acids, but greatest for de novo synthesized fatty acids
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-40
-20
0
20
40
60
C6 to C14:1 C16 +C16:1 C18 + C18:1
HG/LF dietPlant oil supplement
Fatty Acids
MFD Changes Milk Fat Composition
Bauman and Griinari (2003)
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Biohydrogenation Theory
• MFD is the result of direct inhibition of milk fat synthesis at the mammary gland by unique fatty acid intermediates formed during rumen biohydrogenation of PUFA.
Bauman and Griinari (2003)
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trans‐10, cis‐12 CLA in Milk Fat
-60
-50
-40
-30
-20
-10
0
10
0 0.1 0.2 0.3 0.4 0.5
Change in Milk Fat trans -10, cis -12 CLA, %
Cha
nge
in M
ilk F
at Y
ield
, %
Adapted from de Veth et al. (2004)
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Post‐Ruminal Infusion vs. Diet‐Induced MFD
-60
-50
-40
-30
-20
-10
0
10
0 0.1 0.2 0.3 0.4 0.5
Change in Milk Fat trans -10, cis -12 CLA, %
Cha
nge
in M
ilk F
at Y
ield
, % Infusion
Diet-induced MFD
Adapted from Peterson et al. (2003) and Griinari and Bauman (2005)
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0
1
2
3
4
5
6/8 9 10 11 12 13/14
0
1
2
3
4
5
6/8 9 10 11 12 13/14
Double Bond Position
Compo
sitio
n (%
)Co
mpo
sitio
n (%
)
Normal Milk Fat
MF Depressed
Griinari et al. (1997)
C18:1 trans Fatty Acids
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012345
6/8 9 10 11 12 13/14
012345
6/8 9 10 11 12 13/14
Double Bond Position
Compo
sitio
n (%
)Co
mpo
sitio
n (%
)
Normal Milk Fat
MF Depressed
Linoleic acid
trans‐10, cis‐12 CLA
trans‐10 18:1
Stearic acid (18:0)
Rumenic acid
Vaccenic acid
Stearic acid (18:0)
C18:1 trans Fatty Acids
Griinari et al. (1997)
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.
©2007 by American Society for NutritionLock A L et al. J. Nutr. 2007;137:71-76
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.
Lock A L et al. J. Nutr. 2007;137:71-76©2007 by American Society for Nutrition
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Role for trans‐10 18:1
• trans‐10, cis‐12 CLA is the most extensively studied potent inhibitor of milk fat synthesis
• MFD is correlated with trans‐10 rumen outflow– Does not directly inhibit milk fat synthesis– Marker of altered biohydrogenation
• Other trans and conjugated PUFA may decrease milk fat
Lock et al. (2007)
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Monensin and Milk Fat Depression
• Ionophores disrupt biohydrogenation
• Monensin targets gram positive bacteria– Includes group “B” bacteria that hydrogenate monenes
– Potentially results in build‐up of intermediates– Not a problem in normal biohydrogenation pathways
Fellner et al. (1997)
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Biohydrogenation
Linoleic acid(cis‐9, cis‐12 18:2)
trans‐10, cis‐12 CLA
trans‐10 18:1
Stearic acid (18:0)
Rumenic acid(cis‐9, trans‐11 CLA)
Vaccenic acid(trans‐11 18:1)
Stearic acid (18:0)
1) Isomerization
2) Hydrogenation
Group “A”
3) HydrogenationGroup “B”Monensin‐targeted
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Monensin and Milk Fat Depression
• No single risk factor for MFD
• Monensin has potential to amplify the effect of other risk factors
• Monensin decreased milk fat content 0.13%
• Decreases in fat yield seem related to increased presence of dietary unsaturated FA
Duffield et al. (2008)
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Rumen Unsaturated FA Load
• RUFAL reflects total dietary unsaturated FA supply entering the rumen daily– Total feed ingredient fatty acid composition
• Oleic (C18:1)• Linoleic (C18:2)• Linolenic (C18:3)
– Marker for altered biohydrogenation
Lock and Jenkins (2009)
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Unsaturated FA ×Monensin
• Lack of available data to support interaction of monensin and unsaturated FA
• Heterogeneity of data in meta‐analysis
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0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 0.5 1 1.5 2 2.5 3 3.5Dietary C18:1 % DM
Die
tary
C18
:2 %
DM
37
Dietary C18:1 and C18:2 Concentrations
37
MOML (7.0%)
HOLL (7.0%)MOLL (5.9%)
NoFat (3.0%)
LOML (5.9%)
LOLL (4.7%)
LOHL (7.0%)
• Total dietary EE% in parentheses• 6 fat blend trts test C18:1, C18:12, C18:2, C18:22, C18:1×C18:2 interaction
©Ming and Armentano; 2010, UW‐Madison
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No monensin×C18:1 or C18:2 effect on milk fat yield
©Ming and Armentano; 2010, UW‐Madison
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Monensin and Milk Fat Depression
• Monensin changes the rumen environment
• Diets with the capacity to lead to MFD are further influenced by monensin
• With most diets, an effect is not observed and reductions are only apparent for content, not yield
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http://inventorspot.com/articles/food_sculpture_16966
“Butter is just a little stick of smiles and happiness” – Paula Deen
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Increasing Milk Fat Yield
• Milk fat composition is easily manipulated
• Increases with saturated LCFA infusion– Decreases proportion of de novo FA– Unsaturated FA can reduce DMI
• LCFA are derived from dietary sources
• Short‐ and medium‐chain FA are essential for milk triacylglycerol synthesis
Kadegowda et al. (2008)
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Abomasal Butterfat Infusion
• Treatments:– 400 g/d butterfat – 245 g/d LCFA mixture matching LCFA in butterfat
• Compare effects of short‐ and medium‐chain FA
• Limited infusions to avoid DMI reduction
Kadegowda et al. (2008)
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Kadegowda et al. (2008)
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Abomasal Infusion of Butterfat Increases Milk Fat Yield
Item Control Butterfat LCFA SEMMilk, kg/d 31.8 33.7 33.1 2.5FCM, 3.5% 32.87 37.72 35.04 2.71Fat, % 3.74 4.26 3.79 0.19Fat yield, g/d 1,178 1,421 1,279 107.7
Kadegowda et al. (2008)
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Abomasal Infusion of Butterfat Increases Milk Fatty Acid Yields
Kadegowda et al. (2008)
0
50
100
150
200
250
300
350
400
450
500
<16:0 16:00 >16:0 MUFA PUFA
g of FA
ME/d
Control
Butterfat
LCFA
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Increasing Milk Fat Yield
• Infusion of LCFA did not alter milk fat yield– FA <16:0 were not reduced, but maintained
• Butterfat and LCFA similarly increased FA >16:0– Changes in palmitate to stearate ratios may have influenced LCFA treatment fat yields
• Medium‐chain FA transfer efficiency increased with chain length– Yield of 14:0 was greater for cows infused with butterfat
• Short‐ and medium‐chain FA may be limiting factors for increasing milk fat synthesis
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Take Home Message
• Milk fat yield can be increased with fat supplementation
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Take Home Message
• Milk Fat Depression requires:– Altered rumen environment– Supply of PUFA
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Take Home Message
• No single factor is responsible for MFD –interactions of potential risk factors can change the rumen environment and increase MFD risk.
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Questions?