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Department of Animal Science, Cornell University, Ithaca, NY 14853
2To whom correspondence should be addressed. E-mail: deb6{at}cornell.edu.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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9-desaturase activity
was inhibited at the two high doses of trans-10,
cis-12 CLA, but was unaffected by the low dose. Results
indicate minimal quantities of trans-10,
cis-12 CLA (0.016% of dietary dry matter)
markedly inhibited milk fat synthesis (25% reduction) and that a
curvilinear reduction in milk fat yield occurred with increasing
quantities of trans-10, cis-12 CLA.
KEY WORDS: • conjugated linoleic acid • milk fat • lactation • fatty acids • cows
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. One effect is on nutrient
partitioning in which CLA have been shown to dramatically alter lipid
metabolism during lactation and growth. Dietary supplements of CLA
reduce milk fat synthesis in lactating cows (2
3
4)
, pigs
(5)
and women (6)
, and decrease body fat
content of several species of growing animals (7
8
9
10
11)
.
Most investigations of lipid metabolism in lactating and growing
animals have used commercial supplements containing a mixture of CLA
isomers. As a consequence, it was unclear whether the physiological
effects were attributable to specific isomers. We recently demonstrated
that the trans-10, cis-12 CLA isomer inhibited
milk fat synthesis in dairy cows, but the cis-9,
trans-11 CLA had no effect (12)
. The
trans-10, cis-12 CLA isomer has also been shown
to elicit the reduction in body fat content of growing mice
(13)
.
The dietary level of CLA supplement used to reduce body fat content of
growing animals is typically 0.5–2.0% [see summary by Baumgard et
al. (14)
]. These supplements provided dietary levels of
trans-10, cis-12 CLA ranging from 0.2 to 0.5%.
In contrast, the quantity of CLA required to induce a substantial
reduction in milk fat synthesis in lactating animals is considerably
less. For example, a mixture of CLA isomers at 0.23% of dry matter
intake caused a reduction of >50% in milk fat yield (2)
,
and abomasal infusion of trans-10, cis-12 CLA at
a level of 10 g/d (0.05% of diet) resulted in a 44% reduction in milk
fat yield (12)
. However, there have been no
dose-response studies with pure CLA isomers, and accurate
comparisons among studies are difficult because of differences in the
content and isomer composition of CLA supplements. Our objective was to
determine the milk fat response to differing amounts of
trans-10, cis-12 CLA in lactating dairy cows. We
previously established that milk fat content of de novo synthesized
fatty acids and fatty acid products of
9-desaturase were markedly reduced during
abomasal infusion of trans-10, cis-12 CLA
(12)
. Effects on milk fat composition relate to the
potential mechanisms of action; therefore, a second objective was to
examine effects on milk fatty acid composition across the range of
trans-10, cis-12 CLA doses.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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All procedures involving animals were approved by the Cornell
University Institutional Animal Care and Use Committee. Multiparous
lactating Holstein cows (n = 4; 228 ± 54 d postpartum; mean ± SD) fitted with rumen fistulas
were randomly assigned in a 4 x 4 Latin square experiment. Cows
(608 ± 40 kg body weight) were housed in metabolic tie stalls in
an environmentally controlled room (23°C) with artificial ventilation
and 24-h lighting. They were fed a total mixed ration formulated using
the Cornell Net Carbohydrate and Protein System (15)
. The
diet was formulated to meet or exceed the predicted requirements for
energy, protein, minerals and vitamins (16)
. Chopped
alfalfa hay was the major forage component and cracked shelled corn the
primary concentrate (Table 1
). Cows consumed feed ad libitum with equal portions of fresh feed given
twice daily at 0600 and 1800 h. Orts were weighed and recorded on
a daily basis. Water was available at all times.
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. The CLA supplement was emulsified in skim milk to obtain an adequate
volume so that infusions would provide a uniform and continuous supply
of CLA. Emulsions were prepared each experimental period using a
microfluidizer as previously described (2)
. A daily volume
of 4 L of emulsion was infused; the concentrations of
trans-10, cis-12 CLA in emulsions were 0, 0.088,
0.175 and 0.350% for the 0, 3.5, 7.0 and 14.0 g/d doses, respectively.
Skim milk (control infusate) and the emulsions of CLA supplement were
stored at 4°C until infused.
|
. Emulsions were continuously infused
using pumps (Plum Infusion System XL 11555; Abbott Laboratories, North
Chicago, IL) that were programmed to provide the 4 L volume over a 24-h
period. Cows were milked at 0600 and 1800 h daily. Yield was determined and samples taken from each milking. One aliquot was stored at 4°C with a preservative (bronopol tablet; D&F Control System, San Ramon, Ca) until analyzed for fat and protein by infrared analysis (New York DHI, Ithaca, NY). A second aliquot was stored at -20°C until analyzed for fatty acid composition.
Fatty acid analysis.
Milk fat was extracted according to Hara and Radin (18)
and transesterified according to the method of Christie
(19)
with modifications (2)
. Fatty acid
methyl esters were quantified using a gas chromatograph (Hewlett
Packard GCD system HP 6890+; Avondale, PA) equipped with a SP-2560
fused silica capillary column [100 m x 0.25 mm (i.d.) with
0.2-µm film thickness; Supelco, Bellefonte, PA]. The
oven temperature was initially 80°C then ramped at 2°C/min to
190° and maintained for 15 min. Inlet and detector temperatures were
250°C and the split ratio was 100:1. The hydrogen carrier gas flow
rate was 1 mL/min. Hydrogen flow to the detector was 25 mL/min, airflow
was 400 mL/min, and the flow of nitrogen make up gas was 45 mL/min.
Peaks were identified using pure methyl ester standards (Nu-Chek Prep,
Elysian, MN). Additional standards for CLA isomers were obtained from
Natural Lipids. A butter oil reference standard (CRM 164; Commission of
the European Community Bureau of References, Brussels, Belgium) was
used to determine recoveries and correction factors for individual
fatty acids. High resolution nuclear magnetic resonance spectroscopy
(13C) verified that the CLA supplement was comprised almost
exclusively of the trans-10, cis-12 CLA
isomer (M. Aursand and A. Sæbø, Natural Lipids; personal
communication).
Statistical analysis.
Data were statistically analyzed as a 4 x 4 Latin square design
using the PROC MIXED procedure of SAS (20)
according to
the following model
 |
where Yijk is observation, µ is overall mean, Di is dose (i = 1, 2, 3 and 4), Pj is period (j = 1, 2, 3 and 4), Ck is cow (k = 1, 2, 3 and 4) and Eijk is residual error. Orthogonal contrasts were used to test for linear, quadratic and cubic effect of dose. Correlations among measurements were computed using the PROC REG procedure of SAS. To verify treatment effects and control for existing conditions, performance data were covariantly adjusted for preinfusion values. The only performance variable for which this had an effect was dry matter intake.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. The only other notable CLA isomer was
cis-9, trans-11 which represented 2.3% of the
total CLA isomers. All doses of trans-10, cis-12
CLA significantly reduced milk fat yield and content without affecting
milk yield, milk protein percentage or protein yield (Table 3
). Reductions in yield of milk fat ranged from 25% with the lowest dose
(3.5 g/d) to 50% with the highest dose (14.0 g/d) of
trans-10, cis-12 CLA. The temporal pattern of
milk fat content and yield demonstrated that effects on milk fat were
progressive over the first days of infusion, reaching a nadir by d 4
and 5 (Fig. 1
). Feed intake was slightly lower when cows received the two highest
doses (Table 3)
. However, when intake data were covariately adjusted
for preinfusion values, there were no treatment differences
(P = 0.10).
|
|
. The trans-10, cis-12 C18:2
isomer was undetectable (<0.01 g/100 g fatty acids) in milk fat during
the control period (zero dose), but concentrations increased to 0.7
g/100 g fatty acids when cows received the highest trans-10,
cis-12 CLA dose. Increased concentration of
trans-10, cis-12 CLA in milk fat was apparent for
all CLA doses by d 1 of infusion, and progressively increased reaching
a plateau by d 3. During infusion periods, the increase in milk fat
content of trans-10, cis-12 CLA closely
paralleled the pattern of decrease in milk fat yield and content. This
inverse relationship between milk fat percentage and milk fat content
of trans-10, cis-12 CLA is further illustrated in
Figure 3
in which values for individual cows are presented for each milking over
the last 2 d of CLA infusion. Transfer of abomasally infused
trans-10, cis-12 CLA to milk fat averaged 20.9
± 4.1% (mean ± SD for d 4 and 5) and ranged
from 24.9% for the low dose to 16.8% when cows received the high dose
(data not shown).
|
|
). Percentages of most C6 to
C14 fatty acids were reduced in cows receiving
the 3.5 and 7.0 g/d dose of trans-10, cis-12 CLA
and all were decreased in milk fat when cows were abomasally infused
with the highest dose. As a consequence, there was a corresponding
increase in the concentration of most long-chain fatty acids.
Infusion of trans-10, cis-12 CLA also altered
those fatty acids that are substrates and products of
9-desaturase (Table 4)
. Ratios of myristic to
myristoleic acid, stearic to oleic acid, and vaccenic acid to
cis-9, trans-11 C18:2 were
significantly increased in milk fat from cows receiving the highest
dose but were not affected by the lowest dose of trans-10,
cis-12 CLA. A similar trend was evident for the palmitic to
palmitoleic acid ratio, another precursor-product pair for
9-desaturase.
|
), and the decrease involved yields of all fatty acids. However, the
pattern (de novo vs. preformed) of reductions in yield of fatty acids
differed among treatments (Fig. 5
). In particular, the proportion of the reduced yield of milk fat varied
for de novo synthesized fatty acids (<C16),
representing 28, 44 and 47% of the decrease (mmol basis) for the 3.5,
7.0 and 14.0 g/d doses of trans-10, cis-12 CLA.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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3
4)
. On the basis of changes in
milk fat composition observed during diet-induced milk fat
depression (MFD) (21)
, we speculated that effects were due
to CLA isomers containing a trans-10 double bond
(12)
. Indeed, we showed that by d 4 of abomasal infusion,
10 g/d of trans-10, cis-12 CLA caused a 44%
decrease in milk fat yield, whereas infusing a similar amount of
cis-9, trans-11 CLA had no effect
(12)
. The present dose-response study extends these
results. We observed that trans-10, cis-12 CLA
resulted in a curvilinear reduction in milk fat ranging from 25% with
abomasal infusion of 3.5 g/d to 50% with 14.0 g/d (Fig. 4)
. Both the
temporal pattern and the magnitude of milk fat reduction observed in
the present study are consistent with our earlier work using a mixture
of CLA isomers (2
,3)
or a single dose of pure
trans-10, cis-12 CLA (12)
.
Milk fatty acid composition differs among species, but overall, the
fatty acid pattern must yield a triglyceride with fluidity properties
allowing for fat secretion (22)
. In dairy cattle, milk
fatty acids originate from de novo synthesis (short- and
medium-chain fatty acids plus a portion of palmitic and
palmitoleic acids) and the uptake of preformed lipids (a portion of
palmitic and palmitoleic acids plus all longer-chain fatty acids)
(23)
. In this study, the three doses of
trans-10, cis-12 CLA resulted in a reduction in
the yield of most fatty acids. On a molar basis, fatty acids
<C18:0 accounted for 
72% of the decline with
the two high doses of trans-10, cis-12 CLA (7.0
and 14.0 g/d) (Fig. 5)
. This change in milk fatty acid composition is
similar to our previous results with a 10.0 g/d dose of
trans-10, cis-12 CLA (12)
and
suggests that the mechanism may involve primarily an inhibition of de
novo synthesis of fatty acids. However, at the lowest dose of
trans-10, cis-12 CLA (3.5 g/d), in which milk fat
yield was decreased by 25%, the reduction among fatty acids was more
equally distributed between short- and medium-chain fatty acids
(28%), palmitic and palmitoleic acids (35%) and longer-chain
fatty acids (36%) (Fig. 5)
. Thus, the mechanism of inhibition must
also include a substantial reduction in uptake or utilization of
preformed fatty acids. Consistent with this, CLA supplements have been
reported to decrease milk fat in nursing women (6)
and
lactating sows (5)
, two species in which milk fatty acids
are derived predominantly from mammary uptake of preformed lipids.
Dietary CLA supplements have been shown to inhibit the enzyme activity
and gene expression of hepatic 9-desaturase in
rodents (24
,25)
. In vitro studies have shown that the
specific isomer responsible for this effect is trans-10,
cis-12 CLA (26)
. Desaturase in the mammary
gland has a critical effect on milk fat fluidity by introducing a
cis-9 double bond in fatty acids; the most notable
precursor:product pairs are
C14:0/C14:1,
C16:0/C16:1 and
C18:0/C18:1. Changes in
milk fatty acid ratios for these desaturase pairs indicate that
trans-10, cis-12 CLA reduced
9-desaturase when cows received the two
highest doses (Table 2)
. This is similar to our previous observations
with a CLA supplement containing a mixture of isomers (2)
and pure trans-10, cis-12 CLA at 10 g/d
(12)
. However, the lowest dose of trans-10,
cis-12 CLA (3.5 g/d) did not significantly alter the ratios
for the desaturase pairs even though milk fat yield was reduced 25%.
Therefore, a reduction in desaturase does not appear to be a
prerequisite for the decrease in milk fat yield, although it has
traditionally been observed when cows receive CLA supplements or pure
trans-10, cis-12 CLA.
The quantity of CLA as a percentage of diet required to substantially
reduce milk fat synthesis in lactating cows is markedly lower than that
required to reduce the body fat content of growing animals [see
summary by Baumgard et al. (14)
]. For example, abomasally
infusing a CLA supplement at 0.23% of the dietary dry matter reduced
milk fat yield by >50% (2)
, but a similar dietary CLA
supplement fed at 1.0% of the diet reduced fat accretion only by 31%
in growing pigs (10)
. Feeding purified
trans-10, cis-12 CLA at 0.25% of the diet
reduced body fat content of growing mice by >70% (13)
.
The potency of trans-10, cis-12 CLA is further
illustrated in our experiment in which trans-10,
cis-12 CLA at 0.016% of dry matter intake (3.5 g/d) reduced
milk fat yield by 25%.
Recent work has suggested a role for trans-10,
cis-12 CLA in diet-induced low fat milk syndrome,
commonly referred to as MFD in lactating dairy cows. MFD is caused by a
range of diets and prerequisites include an altered rumen environment
and the presence of dietary polyunsaturated fatty acids
(27)
. Thus, it appears that under certain dietary
conditions, rumen fermentation is altered so that the initial
biohydrogenation reaction is isomerization of the cis-9
double bond of linoleic acid yielding trans-10,
cis-12 C18:2, rather than the typical
isomerization of the cis-12 double bond producing
cis-9, trans-11 C18:2 [see
review by Bauman et al. (28)
]. Although rumen production
of trans-10, cis-12 CLA has not been quantified
with diet-induced MFD, there is a curvilinear relationship between
the reduction in milk fat yield and the increase in milk fat content of
trans-10, cis-12 C18:2
(29)
. This relationship is similar to the present study
with abomasal infusions of varying doses of trans-10,
cis-12 CLA. In addition, changes in milk fat composition
during diet-induced MFD (27)
are similar to those
observed in this study. The milk fat content of trans-10,
cis-12 CLA during diet-induced MFD is 0.10–0.15%
(29
,30)
, which is similar to that observed in milk fat
from cows receiving the low dose of trans-10,
cis-12 CLA. However, differences in the magnitude of the
reduction in milk fat suggest that additional unique biohydrogenation
intermediates may inhibit milk fat synthesis, e.g.,
trans-10, cis-12, cis-15 conjugated
octadecatrienoic acid, the intermediate formed in the isomerization of
the cis-9 double bond of 
-linolenic acid
(29)
. Indeed, Chouinard et al. (3)
reported
that a CLA supplement containing cis/trans 8,10
also caused MFD.
The biological mechanism(s) by which trans-10,
cis-12 CLA exerts its effects on lipid metabolism in
lactating animals is unknown, but clearly complex and multifaceted.
Reduced rates of lipogenesis are one mechanism by which it could
influence fatty acid synthesis, and this appears to be a major point of
inhibition, especially with the two highest doses of
trans-10, cis-12 CLA. Presumably, this would
involve changes in key lipogenic enzymes such as acetyl CoA carboxylase
and fatty acid synthetase. This is supported by our recent studies
indicating that trans-10, cis-12 CLA, but not the
cis-9, trans-11 CLA isomer, reduced the
expression of fatty acid synthetase in cultures of bovine mammary
epithelial cells (31)
. However, changes in milk fat
composition from cows receiving the lowest dose of trans-10,
cis-12 CLA indicate that mammary uptake or utilization of
preformed fatty acids was equally reduced. This may be the result of
decreased lipoprotein lipase as has been reported for CLA effects in
cultures of 3T3-L1 adipocytes (13)
.
This is the first dose-response trial using pure trans-10, cis-12 CLA to evaluate effects on milk fat synthesis. Results indicate that extremely low levels (3.5 g/d, 0.016% of diet dry matter) of trans-10, cis-12 CLA reduce milk fat yield by 25% and that 14.0 g/d of trans-10, cis-12 CLA inhibits milk fat synthesis by 50%. Further research is required to determine the mechanism by which trans-10, cis-12 CLA inhibits milk fat synthesis and to quantify rumen production of this CLA isomer under dietary conditions that result in MFD.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Manuscript received November 27, 2000. Initial review completed February 1, 2001. Revision accepted March 16, 2001.
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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J. K. Kay, T. R. Mackle, D. E. Bauman, N. A. Thomson, and L. H. Baumgard Effects of a Supplement Containing Trans-10, Cis-12 Conjugated Linoleic Acid on Bioenergetic and Milk Production Parameters in Grazing Dairy Cows Offered Ad Libitum or Restricted Pasture J Dairy Sci, February 1, 2007; 90(2): 721 - 730. [Abstract] [Full Text] [PDF]
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L. J. Odens, R. Burgos, M. Innocenti, M. J. VanBaale, and L. H. Baumgard Effects of Varying Doses of Supplemental Conjugated Linoleic Acid on Production and Energetic Variables During the Transition Period J Dairy Sci, January 1, 2007; 90(1): 293 - 305. [Abstract] [Full Text] [PDF]
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 R. J. Wynn, Z. C. T. R. Daniel, C. L. Flux, J. Craigon, A. M. Salter, and P. J. Buttery Effect of feeding rumen-protected conjugated linoleic acid on carcass characteristics and fatty acid composition of sheep tissues J Anim Sci, December 1, 2006; 84(12): 3440 - 3450. [Abstract] [Full Text] [PDF]
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 L. Badinga and E. S. Greene Physiological Properties of Conjugated Linoleic Acid and Implications for Human Health Nutr Clin Pract, August 1, 2006; 21(4): 367 - 373. [Abstract] [Full Text] [PDF]
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J. W. Perfield II, P. Delmonte, A. L. Lock, M. P. Yurawecz, and D. E. Bauman Trans-10, trans-12 conjugated linoleic acid does not affect milk fat yield but reduces delta9-desaturase index in dairy cows. J Dairy Sci, July 1, 2006; 89(7): 2559 - 2566. [Abstract] [Full Text] [PDF]
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A. L. Lock, B. M. Teles, J. W. Perfield II, D. E. Bauman, and L. A. Sinclair A Conjugated Linoleic Acid Supplement Containing trans-10, cis-12 Reduces Milk Fat Synthesis in Lactating Sheep J Dairy Sci, May 1, 2006; 89(5): 1525 - 1532. [Abstract] [Full Text] [PDF]
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E. Apper-Bossard, J. L. Peyraud, P. Faverdin, and F. Meschy Changing Dietary Cation-Anion Difference for Dairy Cows Fed with Two Contrasting Levels of Concentrate in Diets J Dairy Sci, February 1, 2006; 89(2): 749 - 760. [Abstract] [Full Text] [PDF]
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M. J. de Veth, S. K. Gulati, N. D. Luchini, and D. E. Bauman Comparison of Calcium Salts and Formaldehyde-Protected Conjugated Linoleic Acid in Inducing Milk Fat Depression J Dairy Sci, May 1, 2005; 88(5): 1685 - 1693. [Abstract] [Full Text] [PDF]
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E. Castaneda-Gutierrez, T. R. Overton, W. R. Butler, and D. E. Bauman Dietary Supplements of Two Doses of Calcium Salts of Conjugated Linoleic Acid During the Transition Period and Early Lactation J Dairy Sci, March 1, 2005; 88(3): 1078 - 1089. [Abstract] [Full Text] [PDF]
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R. Ringseis, D. Saal, A. Muller, H. Steinhart, and K. Eder Dietary Conjugated Linoleic Acids Lower the Triacylglycerol Concentration in the Milk of Lactating Rats and Impair the Growth and Increase the Mortality of their Suckling Pups J. Nutr., December 1, 2004; 134(12): 3327 - 3334. [Abstract] [Full Text] [PDF]
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L. S. Piperova, U. Moallem, B. B. Teter, J. Sampugna, M. P. Yurawecz, K. M. Morehouse, D. Luchini, and R. A. Erdman Changes in Milk Fat in Response to Dietary Supplementation with Calcium Salts of Trans-18:1 or Conjugated Linoleic Fatty Acids in Lactating Dairy Cows J Dairy Sci, November 1, 2004; 87(11): 3836 - 3844. [Abstract] [Full Text] [PDF]
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D. G. Peterson, E. A. Matitashvili, and D. E. Bauman The Inhibitory Effect of trans-10, cis-12 CLA on Lipid Synthesis in Bovine Mammary Epithelial Cells Involves Reduced Proteolytic Activation of the Transcription Factor SREBP-1 J. Nutr., October 1, 2004; 134(10): 2523 - 2527. [Abstract] [Full Text] [PDF]
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J. W. Perfield II, A. L. Lock, A. M. Pfeiffer, and D. E. Bauman Effects of Amide-Protected and Lipid-Encapsulated Conjugated Linoleic Acid (CLA) Supplements on Milk Fat Synthesis J Dairy Sci, September 1, 2004; 87(9): 3010 - 3016. [Abstract] [Full Text] [PDF]
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T. R. Overton and M. R. Waldron Nutritional Management of Transition Dairy Cows: Strategies to Optimize Metabolic Health J Dairy Sci, July 1, 2004; 87(13_suppl): E105 - 119. [Abstract] [Full Text] [PDF]
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C. E. Moore, H. C. Hafliger III, O. B. Mendivil, S. R. Sanders, D. E. Bauman, and L. H. Baumgard Increasing Amounts of Conjugated Linoleic Acid (CLA) Progressively Reduces Milk Fat Synthesis Immediately Postpartum J Dairy Sci, June 1, 2004; 87(6): 1886 - 1895. [Abstract] [Full Text] [PDF]
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J. W. Perfield II, A. Saebo, and D. E. Bauman Use of Conjugated Linoleic Acid (CLA) Enrichments to Examine the Effects of trans-8, cis-10 CLA, and cis-11, trans-13 CLA on Milk-Fat Synthesis J Dairy Sci, May 1, 2004; 87(5): 1196 - 1202. [Abstract] [Full Text] [PDF]
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M. H. Gillis, S. K. Duckett, J. R. Sackmann, C. E. Realini, D. H. Keisler, and T. D. Pringle Effects of supplemental rumen-protected conjugated linoleic acid or linoleic acid on feedlot performance, carcass quality, and leptin concentrations in beef cattle J Anim Sci, March 1, 2004; 82(3): 851 - 859. [Abstract] [Full Text] [PDF]
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K. T. Selberg, A. C. Lowe, C. R. Staples, N. D. Luchini, and L. Badinga Production and Metabolic Responses of Periparturient Holstein Cows to Dietary Conjugated Linoleic Acid and trans-Octadecenoic Acids J Dairy Sci, January 1, 2004; 87(1): 158 - 168. [Abstract] [Full Text] [PDF]
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 T. M. Larsen, S. Toubro, and A. Astrup Efficacy and safety of dietary supplements containing CLA for the treatment of obesity: evidence from animal and human studies J. Lipid Res., December 1, 2003; 44(12): 2234 - 2241. [Abstract] [Full Text] [PDF]
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A. A. AbuGhazaleh, D. J. Schingoethe, A. R. Hippen, and K. F. Kalscheur Conjugated Linoleic Acid and Vaccenic Acid in Rumen, Plasma, and Milk of Cows Fed Fish Oil and Fats Differing in Saturation of 18 Carbon Fatty Acids J Dairy Sci, November 1, 2003; 86(11): 3648 - 3660. [Abstract] |
