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Departments of
*
Animal Science and
Food Science, Cornell University, Ithaca, NY 14853
4To whom correspondance should be addressed.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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KEY WORDS: • cows • conjugated linoleic acid • lactation • fatty acids • milk fat
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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, Ip et al. 1994
), antiobesity effect
(Park et al. 1997
), modulation of the immune system
(Cook et al. 1993
) and reductions in atherogenesis
(Nicolosi et al. 1997
) and diabetes (Houseknecht et al. 1998
). The specific CLA isomer(s) responsible for these
various biological effects has not been clearly established, although
cis-9, trans-11 CLA is thought to be key in the
anticarcinogenic effects (Ha et al. 1990
, Ip et al. 1991
).
Food products from ruminants, particularly dairy products, are the
major dietary source of CLA for humans. CLA are intermediates in the
biohydrogenation of linoleic acid, and it is generally accepted that
CLA in ruminants originate from the incomplete biohydrogenation of
unsaturated fat by rumen bacteria (Kelly et al. 1998
).
However, recent work has demonstrated that cows can also synthesize CLA
from trans-11 octadecenoic acid, another intermediate in the
rumen biohydrogenation process (Griinari et al. 1998b
).
The major CLA isomer in food products from ruminants is
cis-9, trans-11, although other CLA isomers are
present and these may vary under different rumen conditions
(Griinari et al. 1997a
, Ha et al. 1989
).
CLA levels in food products derived from ruminants can be altered by affecting ruminal production of CLA or trans-11 18:1, or by dietary supplement with these fatty acids. Our objective was to examine the effect of dietary supplementation of CLA on performance and milk composition of dairy cows, and the efficiency with which CLA were transferred to milk fat. To do this, we utilized a commercial source of CLA that represented a mixture of CLA isomers; the CLA supplement was infused abomasally to by-pass rumen fermentation processes.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Four multiparous Holstein cows (258 ± 43 d postpartum; mean
± SD) fitted with rumen fistulas were used. Cows were
fed a total mixed diet formulated according to the Cornell Net
Carbohydrate and Protein System (Fox et al. 1992
,
Russell et al. 1992
, Sniffen et al. 1992
). The major forage component was chopped alfalfa hay and
the major concentrate component was cracked shelled corn (Table 1
). The diet contained 16.3% crude protein and net energy for lactation
of 6.54 MJ/kg (dry matter basis), and was balanced for protein, energy,
minerals and vitamins to meet the predicted requirements (NRC
1989
). Cows were fed ad libitum with equal portions of feed
were offered every other hour to minimize postprandial effects on
nutrient supply. In addition, water was available at all times.
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Abomasal infusions involved a 0.5-mm (i.d.) Nalgen tubing that passed
through the rumen fistula and sulcus omasi into the abomasum as
previously described (Griinari et al. 1997b
). Emulsions
were continuously infused by a peristaltic pump (Harvard Apparatus,
South Natick, MA) calibrated to deliver 5 L/d. A sanitized carboy
served as the reservoir for the emulsion; the carboy and emulsions were
replaced daily.
Cows were milked at 600 and 1800 h daily. At each milking, yield
was determined and milk was sampled. 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 content by infrared analysis
(New York DHI, Ithaca, NY). Because of the low milk fat content
observed for some milk samples, we verified the accuracy of the
infrared analysis of milk fat according to Association of Official
Analytical Chemists [method #989.05; (AOAC 1995
)] and
results were in agreement (±3%). A second set of milk samples without
preservative was combined proportionately to milk yield on an
individual cow basis for each day and stored at -20°C until analyzed
for fatty acid composition.
For fatty acid analysis, an aliquot of thawed milk (~30 mL) was
centrifuged at 17,800 x g for 30 min at 8°C, and
then 300–350 mg of fat cake were removed. Lipid extraction of milk fat
was performed according to Hara and Radin (1978)
using a
hexane/isopropanol (3:2, v/v) solution (18 mL/g of fat cake) followed
by a 67 g/L sodium sulfate solution (12 mL/g of fat cake). Milk fatty
acids were transesterified with sodium methoxide prepared in our
laboratory according to the method of Christie (1982)
with modifications. The sodium methylate was obtained from Fluka Chemie
Ag (Buchs, Switzerland). Hexane (2 mL) was added to 40 mg of butter oil
followed by 40 µL of methyl acetate. After the mixture was
vortexed, 40 µL of methylation reagent (1.75 mL
methanol:0.4 mL of 5.4 mol/L sodium methylate) was added. The mixture
was vortexed and allowed to react for 10 min; then 60 µL
of termination reagent (1 g oxalic acid/30 mL diethyl ether) was added.
The sample was then centrifuged for 5 min at 2400 x g
at 5°C leaving a clear layer of hexane; an aliquot of the hexane was
taken and used directly for chromatographic determination.
Fatty acid methyl esters (FAME) in hexane were then injected (split inlet 87.5:1) into a gas chromatograph (Hewlett Packard GCD system HP G1800 A; Avondale, PA) equipped with an electron ionization detector. Separation of FAME was performed with a Supelcowax-10 fused silica capillary column [60 m x 0.32 mm (i.d.), with 0.25-µm film thickness] (Bellefonte, PA). Helium was used as the carrier gas. The oven temperature was programmed from 50 to 190°C at 10°C/min and held for 41.5 min. Injector and detector were at 250°C. Peak area was measured using a HP G107A GCD integrator. Each peak was indentified and quantified using pure methyl ester standards (Nu-Chek-Prep, Elysian, MN).
For the fatty acid analysis of CLA supplement, free fatty acids were
methylated using 1% sulfuric acid in methanol as described by
Christie (1989)
. Fatty acid profiles were determined
following the gas chromatographic procedure described for milk fat.
With our particular column and conditions, we were able to obtain
partial separation of distinct peaks of the major CLA isomers
cis/trans (c/t) 8,10,
c/t 9,11, c/t 10,12, and
c/t 11,13. We identified these peaks using pure
standards (Nu-Chek-Prep, Matreya, Pleasant Gap, PA) and various
enrichments of CLA isomers (Natural Lipids). Further, we validated our
ability to determine specific amounts of each CLA isomer from
comparisons with the various CLA isomer mixtures (Natural Lipids).
Data were analyzed as a 4 x 4 Latin square design using the
general linear model models procedure of SAS (1989)
according to the following model:
 |
where Yijkl is the observation, µ is the overall mean, Ti is the treatment (i = 1, 2, 3 and 4), Pj is the period (j = 1, 2, 3 and 4), Ck is the cow (k = 1, 2, 3 and 4) and Eijkl is the residual error. Contrasts were used to test the linear, quadratic or cubic effect of the dose of CLA-60 infusion. Values in the text are presented as means ± SEM.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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). The actual rates of infusion of CLA supplement were 0, 51.2 ± 3.7, 94.3 ± 5.1 and 147.1 ± 6.6 g/d during the four periods
of the experiment for the 0, 50, 100 and 150 g/d treatments,
respectively. Thus, actual amounts of CLA isomers infused for the
treatments were 0, 31.3, 57.7 and 90.0 g/d. When expressed on the basis
of intake, the three levels of CLA isomers represented ~0.14–0.42%
of total dry matter.
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). Moreover, the CLA supplement had minimal effects on milk yield except
at the highest dose (150 g/d). CLA supplement infusion also had no
effect on milk protein content and yield. In contrast, abomasal
infusion of CLA supplement resulted in a dramatic reduction of milk fat
synthesis. The reduction in milk fat was essentially maximized at the
lowest level of CLA supplement infusion (31.3 g/d of total CLA
isomers); this represented a reduction of >50% for both milk fat
content and milk fat yield across the three levels of CLA infusion.
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shows the temporal pattern of milk fat content at each of the twice
daily milkings during the 5-d infusion and the 4-d postinfusion
intervals. The reduction in milk fat was already maximized after 5–6
milkings (d 3 of infusion). During the postinfusion interval, milk fat
progressively increased, but it had not fully returned to normal by
4 d postinfusion. This residual effect resulted in a milk fat
content that averaged only 2.8% on d 0 of the infusion periods (Fig. 1)
. This is lower than typical for the cows used in this study; milk
fat content averaged 3.3% for the four cows during the week preceeding
the initial infusion period. Thus, estimates of the magnitude of milk
fat reduction by CLA infusion represent an underestimate.
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). The proportions of most of these fatty acids (6:0–14:0) were altered
in a quadratic pattern with the decrease already maximized at the
lowest level of CLA supplementation. Moreover, the proportions of 18:0,
18:2 and 18:3 were increased by the infusion of CLA supplement, whereas
18:1 remained unchanged. The ratios of 14:0 to 14:1, 16:0 to 16:1 and
18:0 to 18:1 were increased linearly with increasing amounts of CLA
supplement infused.
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). All of the major CLA isomers present in the CLA supplement were
transferred to milk fat in a dose-dependent manner. The proportion
of each individual isomer increased gradually over the 5-d infusion
interval and had generally reached a plateau by d 4. The apparent
transfer efficiency of the abomasally infused CLA isomers (amount of
isomer excreted in milk fat as a percentage of the amount infused) was
~22–26% for most of the isomers present in the CLA supplement
(Fig. 3
). The exception was the cis/trans 10,12 CLA isomer, which
was transferred to milk fat with a much lower efficiency (10.2%).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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), we infused the CLA supplement abomasally to by-pass
rumen fermentation processes. The addition of the CLA supplement
increased the milk fat content of CLA in a dose-dependent manner
from ~7 mg/g fat at the zero dose to 64 mg/g fat at the high dose of
150 g/d of CLA supplement (90 g/d of actual CLA isomers). The milk
content of CLA had typically reached a constant value by 4–5 d after
initiation of the daily CLA supplement infusion. Milk fat normally
contains cis-9, trans-11 as the major CLA isomer,
whereas the CLA supplement contained a mixture of isomers with
cis/trans 8,10, cis/trans 9,11,
cis/trans 10,12 and cis/trans 11,13 as the major
isomers (Table 2)
. We observed that all of the major isomers in
the CLA supplement were transferred to milk fat in a dose-dependent
manner (Fig. 2)
. However, there were differences among the isomers in
the efficiency of transfer. Only ~10% of the dietary supplement of
cis/trans 10,12 CLA isomer was transferred to milk fat,
whereas the cis/trans 8,10, cis/trans 9,11 and
cis/trans 11,13 CLA isomers were transferred to milk fat
with over twice the efficiency (22–26%) (Fig. 3)
.
The abomasal infusion of the CLA supplement had a dramatic effect on
milk fat yield. Across all CLA doses, the content and yield of milk fat
were reduced by 52 and 55%, respectively (Table 3)
. This was
surprising because earlier studies in which lactating rats were fed a
CLA supplement at 0.25 and 0.50% of diet dry matter showed no
indication of reduction in milk fat secretion as indicated by growth
rates of the nursing pups (Chin et al. 1994
).
Loor and Herbein (1998)
also observed a reduction in
milk fat in dairy cows that received a 24-h abomasal infusion of CLA
(100 g). In our study, the reduction in milk fat was of a similar
magnitude at all levels of CLA supplement infusion; the low dose of 50
g/d of CLA supplement (31.3 g/d of CLA isomers) represented a dietary
level of CLA isomers of 0.14% on a dry matter basis.
Certain dietary situations reduce milk fat in lactating cows; this is
referred to as milk fat depression or low milk fat syndrome
(Davis and Brown, 1970
, Sutton, 1989
).
High concentrate diets, addition of rumen-active fats and diets in
which the forage is of small particle size are examples of conditions
that lead to decreased milk fat yield. Typically, these situations
cause reciprocal changes in fat synthesis in which mammary synthesis of
milk fat is reduced and fat accretion in adipose tissue is increased
(Davis and Brown 1970
, Griinari et al. 1997a and 1997b
, Sutton 1989
). It is not known whether a
reciprocal increase in fat synthesis occurred in adipose tissue from
cows exhibiting the CLA-induced reduction in milk fat. However,
reciprocal changes may not have occurred in lactating cows because
dietary CLA supplements (mixture of isomers) have been shown to
decrease body fat accretion in several species of growing animals,
including mice (DeLany et al. 1998
, Park et al. 1997
) and pigs (Cook et al. 1998
, Dugan et al. 1997
, Dunshea et al. 1998
). If fat
accretion was decreased or not altered in the CLA
supplement-infused cows, we would expect voluntary intake to
decrease by an amount energetically equal to the reduction in milk fat.
We observed minimal changes in voluntary intake over the 5-d infusion
period (Table 3)
, but longer-term studies would be required to
assess this adequately.
The effect of the CLA supplement on the performance of lactating cows
was specific for milk fat; the yield of milk protein was not affected,
and effects on milk yield were minimal except at the highest CLA dose
(Table 3)
. The milk fat of dairy cows contains a distinct pattern of
fatty acids that originates from de novo fatty acid synthesis, uptake
of preformed fatty acids and desaturation of a portion of the
long-chain fatty acids. The reduction in milk fat due to the CLA
supplement was relatively greater for the short- and medium-chain
fatty acids (Table 4)
. These represent the portion synthesized de novo
by the mammary epithelial cells. In addition, 
-9 desaturase
catalyzes the desaturation of longer-chain fatty acids, and the
ratios of 14:0 to 14:1, 16:0 to 16:1 and 18:0 to 18:1 were all
increased with CLA supplement infusion (Table 4)
. This raises the
possibility that the mechanism of the CLA inhibition involves both de
novo fatty acid synthesis and the desaturation process. However, it is
important to recognize that the full complement of fatty acids is
required to obtain a pattern of triglycerides with appropriate fluidity
characteristics. Thus, the specific site(s) at which CLA inhibits milk
fat synthesis could involve any of these pathways as well as the
esterification, packaging and secretion of milk fat triglycerides.
It is also not known whether the inhibition of fat synthesis is
specific for one or more of the CLA isomers. We do not think that the
cis-9, trans-11 CLA isomer is involved because we
have observed that milk fat content of cis-9,
trans-11 CLA is not correlated with fat content of milk
(Griinari et al. 1997a
). Furthermore, Lee et al. (1998)
observed that a dietary supplement containing a mixture
of CLA isomers decreased rat liver expression of -9 desaturase mRNA,
but the effect involved isomers other than cis-9,
trans-11 CLA. Recently, we have shown that the classical
diet-induced milk fat depression is associated with an increase in
the milk fat content of trans-10 18:1 (Griinari et al. 1998a
). Thus, it may be that the specific CLA isomers
affecting fat synthesis in the mammary gland (lactation) and adipose
tissue (growth) are those with a trans-10 double bond
(cis-8, trans-10 CLA and trans-10,
cis-12 CLA).
Overall, this study demonstrated that the milk fat content of CLA can be increased via CLA supplement infusion. However, the most pronounced effect of the CLA supplement was to cause a reduction in milk fat yield of >50% and a shift in the fat composition to more long-chain fatty acids. The possibility of specific roles for the different CLA isomers and the specific site(s) of inhibition of mammary synthesis of milk fat remain to be elucidated.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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2 Supported in part by Dairy Management,
(Rosemont, IL), Northeast Dairy Foods Research Center and the Cornell
Agricultural Experiment Station.
3 Current address: Département des sciences
animales, Pavillon Paul-Comtois, Université Laval,
Québec, Canada G1K 7P4.
5 Abbreviation used: c,
cis; CLA, conjugated linoleic acids, FAME, fatty acid
methyl esters; t, trans.
Manuscript received October 16, 1998. Initial review completed January 13, 1999. Revision accepted April 27, 1999.
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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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K. J. Harvatine and M. S. Allen Effects of Fatty Acid supplements on milk yield and energy balance of lactating dairy cows. J Dairy Sci, March 1, 2006; 89(3): 1081 - 1091. [Abstract] [Full Text] [PDF]
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S. L. Allred, T. R. Dhiman, C. P. Brennand, R. C. Khanal, D. J. McMahon, and N. D. Luchini Milk and Cheese from Cows Fed Calcium Salts of Palm and Fish Oil Alone or in Combination with Soybean Products J Dairy Sci, January 1, 2006; 89(1): 234 - 248. [Abstract] [Full Text] [PDF]
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C. Leonardi, S. Bertics, and L. E. Armentano Effect of Increasing Oil from Distillers Grains or Corn Oil on Lactation Performance J Dairy Sci, August 1, 2005; 88(8): 2820 - 2827. [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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C. E. Moore, J. K. Kay, R. J. Collier, M. J. VanBaale, and L. H. Baumgard Effect of Supplemental Conjugated Linoleic Acids on Heat-Stressed Brown Swiss and Holstein Cows J Dairy Sci, May 1, 2005; 88(5): 1732 - 1740. [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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B. J. Bradford and M. S. Allen Milk Fat Responses to a Change in Diet Fermentability Vary by Production Level in Dairy Cattle J Dairy Sci, November 1, 2004; 87(11): 3800 - 3807. [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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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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 J. K. Kramer, C. Cruz-Hernandez, Z. Deng, J. Zhou, G. Jahreis, and M. E. Dugan Analysis of conjugated linoleic acid and trans 18:1 isomers in synthetic and animal products Am. J. Clinical Nutrition, June 1, 2004; 79(6): 1137S - 1145S. [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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V. Bontempo, D. Sciannimanico, G. Pastorelli, R. Rossi, F. Rosi, and C. Corino Dietary Conjugated Linoleic Acid Positively Affects Immunologic Variables in Lactating Sows and Piglets J. Nutr., April 1, 2004; 134(4): 817 - 824. [Abstract] [Full Text] [PDF]
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S. G. Onetti, S. M. Reynal, and R. R. Grummer Effect of Alfalfa Forage Preservation Method and Particle Length on Performance of Dairy Cows Fed Corn Silage-Based Diets and Tallow J Dairy Sci, March 1, 2004; 87(3): 652 - 664. [Abstract] [Full Text] |
